[RayLivingston]

I have an '07 335i. Due to the Corona virus lockdown here in the SF Bay area, we had not driven for 6-7 weeks, until yesterday. All is well, except the AC is totally kaput. It was, briefly, making a strange screeching noise that sounded like it was coming from somewhere in the center console, but that has gone away. Near as I can tell, the AC clutch is never engaging. When I look down the front of the engine with the engine idling, the front of the compressor clutch is NOT spinning.

The climate control panel operates normally. Both fuses associated with the "snowflake" icon (fuses #29 and #60) are fine. There is pressure in the system, about 30PSI static on the low side with engine off. I seem to recall when I topped off the system about 3 years ago that is where it ended up.

When I start then engine, the high side pressure jumps up just very slightly off the bottom of the gauge, I'm guessing to about the same pressure as the low side, then just stays there. Never goes any higher.

Pressing the A/C "snowflake" switch has no visible effect on the compressor, so it appears the clutch has either completely failed, or there is a fault somewhere preventing it from ever being engaged.

I assume there is a low pressure switch somewhere that could cause this. Where is it?

What else should I be looking at/for?

Regards,
Ray L.

[ewicky]

FYI Our aircon compressors don't have a clutch.

[RayLivingston]

Originally Posted by ewicky

FYI Our aircon compressors don't have a clutch.

OK, so what can cause no pressure on the high side?

I'm also a bit confused by your statement. I can Google and find tons of places that will sell me a replacement A/C clutch. And, as I said, when I look at the front of the compressor pulley with the engine running, it is NOT spinning. The belt is moving, the pulley itself is spinning, but the center part of the pulley is sitting still. How can that be?

Regards,
Ray L.

[gbalthrop]

Originally Posted by RayLivingston

...'07 335i...not driven for 6-7 weeks, until yesterday... It was, briefly, making a strange screeching noise [Sound like a slipping Serpentine Belt? Is the belt still intact?] that sounded like it was coming from somewhere in the center console, but that has gone away. Near as I can tell, the AC clutch is never engaging. When I look down the front of the engine with the engine idling, the front of the compressor clutch is NOT spinning. [Do you actually have a compressor CLUTCH? Most E9x models I know of, at least sold in US, have "Compressor Valve" instead of clutch, and NOTHING changes visibly on the front of the compressor, at the drive pulley, between when compressor is "Pumping" (Snowflake LED Lit) or NOT pumping.]

The climate control panel operates normally. Both fuses associated with the "snowflake" icon (fuses #29 and #60) are fine. [I presume your 2007 model was built BEFORE 3/1/2007 if those are correct fuses? (F29 is just AUC) I assume IHKA Climate Control Panel lights & functions as normal & Blower operation is Normal?] There is pressure in the system, about 30PSI static on the low side with engine off. [See Below] I seem to recall when I topped off the system about 3 years ago that is where it ended up.
When I start then engine, the high side pressure jumps up just very slightly off the bottom of the gauge, [Do you mean High Side Pressure was "0" BEFORE engine started? If engine has NOT been run for several hours (Normal A/C Components) the "Equilibrium Pressure" on both sides should be the same, and that should be MORE in the range of 60 PSIG or more. I don't think the IHKA or JBE Modules would activate the Compressor Valve if the "Refrigerant Pressure Sensor, located on the High Side refrigerant line running from the Condenser to the Evaporator, just forward of the Washer Fluid filler tube, did NOT sense pressure higher than 30 PSIG.] I'm guessing to about the same pressure as the low side, then just stays there. Never goes any higher.
Pressing the A/C "snowflake" switch has no visible effect on the compressor, so it appears the clutch has either completely failed, or there is a fault somewhere preventing it from ever being engaged.
I assume there is a low pressure switch somewhere that could cause this. Where is it?

Hi Ray,

First thing is to determine which type of compressor you have. Here are two TIS videos, the first showing the different types, and the second showing one way to test the Compressor Valve (NON-clutch) type:
https://www.newtis.info/tisv2/a/en/e...eos/1VnY9cKgnR
https://www.newtis.info/tisv2/a/en/e...eos/1VnXysZKkb

If the noise you heard on startup after sitting was NOT from the Blower Motor, it must have come from the Compressor or Drive Belt. Please supply any additional description/thoughts on WHAT that noise sounded like, when exactly it occurred, and the SOURCE.

My concern is the fact of the SOUND. If you simply had low refrigerant pressure (BEFORE starting the engine), the compressor clutch or VALVE (?) would NOT have been active and the Compressor would NOT have tried to pump R-134a, and it should NOT have made any noise. You WOULD simply have NO refrigeration. Be aware that if you have the Compressor Valve type compressor, with NO Clutch/Magnetic Coupling, there have been several reports of Pulley Shaft Failure.

Several photos of the front of your compressor would be helpful. Also, precise gauge readings on High & Low side, after engine OFF for several hours, would be helpful, along with Blower Speed function using manual speed buttons on Control Panel. "Static" or "Equilibrium" pressure on High & Low sides should be the same after engine NOT run for hours, and that pressure should be in range of 60 PSIG or more.

I would start with examination & testing of the compressor, testing whether the shaft is intact & can be turned as shown in TIS vidio, and if there IS a magnetic clutch, you can always test that for "click" by applying power with engine OFF.

Please let us know what you find,
George

[gbalthrop]

Originally Posted by RayLivingston

OK, so what can cause no pressure on the high side?
I'm also a bit confused by your statement. I can Google and find tons of places that will sell me a replacement A/C clutch. And, as I said, when I look at the front of the compressor pulley with the engine running, it is NOT spinning. The belt is moving, the pulley itself is spinning, but the center part of the pulley is sitting still. How can that be?

What you describe suggests YOUR compressor does indeed have a clutch, and if you have Refrigeration Manifold Gauge Set and know how to use it, I PRESUME you can tell the difference between the TWO types of Compressors used (see videos linked in my earlier post).

My only concerns are (1) what caused the NOISE, and (2) is compressor type properly identified.

IF equilibrium pressure is 30 PSIG or less on BOTH High & Low sides, then simply adding 12 oz of R-134a (Engine OFF) should allow the compressor clutch/valve to engage and pump refrigerant, which will result in HIGH side pressure going UP, and Low side pressure going DOWN. If that doesn't happen, then your Refrigerant Pressure Sensor or its Connector/ wiring are likely faulty.

CAUTION: IF you have a significantly lower reading on High Side than Low Side with system "at Equilibrium" after engine off for hours, that suggests a blockage or damage somewhere in the system, and I would NOT try to run the engine with compressor "Pumping" until further investigation.

George

[RayLivingston]

George,

Thanks for replying. This thing is driving me nuts!!

Noise - the noise sounded to me more like a noisy expansion valve, though it seemed to be coming from the passenger (RH) side of the center console, and I believe the expansion valve is more over on the driver (LH) side. Turning the "snowflake" switch on and off would make the noise start and stop. Snowflake lit, the noise was present. Snowflake not lit, no noise. Fans work fine, and make normal noise. Also there was NO audible noise in the engine bay with the snowflake on or off. The noise was definitely coming from inside the car (Sounds like the beginning of a bad horror movie...).

Compressor - So it's normal for the center part of the compressor pulley to be stationary when the engine is running?

Fuses - Don't recall when this car was built, but I used the fuse "map" in the fuse box door to identify the appropriate fuses. Those were #29 (5A, located second row from the top, second fuse from the right in the fusebox), and #60 (7.5A, located in the bottom row, 5th fuse from the left). Both are fine.

Climate Control Panel - All functions operate 100% normally, except there is no cold air.

Pressures - I clearly remember when I charged this system, several years ago, ending up with ~35 PSI low-side pressure - could not get it any higher. high side was, IIRC, ~160PSI. The system has worked fine for the last 3 years or so, and worked fine last time we drove it in March. I started it a while ago, and let it run ~10 minutes with AC set to MAX, and low-side crept from 30PSI up to 35PSI, and settled there, but high-side just sat at 0. Never came up at all.

Page 43 of this document:

http://www.ariazone.com/wp-content/u...ing-manual.pdf

indicates 30-35PSI is correct, if not a bit high, for low-side pressure with 134a at 20C, which is where we are today. I can't explain how the high side can be 0. I am going to check again with a different gauge.

I was looking earlier for the pressure switch. It appears to me to be located on the driver side, perhaps alongside the air filter box? I assume it should be closed with there is enough pressure, and can be tested with a continuity tester?

Regards,
Ray L.

[RayLivingston]

OK, two red herrings:

High-side pressure is the same a low-side pressure - 35PSI, engine on or off. My high-side pressure gauge was stuck on 0. I gave it a whack, and it started behaving.

Compressor is spinning. I was looking at the wrong thing. This being a 335i, there is so much in the way it is impossible to see the compressor itself, and only barely possible to see a little bit of the pulley. But I can see the center bolt on the compressor shaft, and it is spinning when the engine is running.

I looked, again, for the pressure switch, and could not find it, again. Is it on the high-side line, on the passenger (RH) side of the car, or on the low-side line, on the driver (LH) side of the car? Is it buried beneath the coolant overflow tank, or the two little vacuum reservoirs, just in front of that?

Regards,
Ray L.

[Unknown_Car]

Originally Posted by RayLivingston

I have an '07 335i. Due to the Corona virus lockdown here in the SF Bay area, we had not driven for 6-7 weeks, until yesterday. All is well, except the AC is totally kaput. It was, briefly, making a strange screeching noise that sounded like it was coming from somewhere in the center console, but that has gone away. Near as I can tell, the AC clutch is never engaging. When I look down the front of the engine with the engine idling, the front of the compressor clutch is NOT spinning.

The climate control panel operates normally. Both fuses associated with the "snowflake" icon (fuses #29 and #60) are fine. There is pressure in the system, about 30PSI static on the low side with engine off. I seem to recall when I topped off the system about 3 years ago that is where it ended up.

When I start then engine, the high side pressure jumps up just very slightly off the bottom of the gauge, I'm guessing to about the same pressure as the low side, then just stays there. Never goes any higher.

Pressing the A/C "snowflake" switch has no visible effect on the compressor, so it appears the clutch has either completely failed, or there is a fault somewhere preventing it from ever being engaged.

I assume there is a low pressure switch somewhere that could cause this. Where is it?

What else should I be looking at/for?

Regards,
Ray L.

I have a ac compressor for sell if interested 50k miles on it. I did a ac delete and it's sitting in the garage.

[RayLivingston]

Originally Posted by Roma_335i

I have a ac compressor for sell if interested 50k miles on it. I did a ac delete and it's sitting in the garage.

Thanks, but I see nothing so far that suggests the compressor is bad. I suspect the pressure switch, or perhaps another !@#$%^&*( rat chewed through some wire somewhere...

Regards,
Ray L.

[RayLivingston]

OK, so I found the pressure sensor (sensor, not switch), just behind the coolant overflow tank, under a heat shield. Since it appears to be an electronic sensor, rather than a simple switch, I see no way of testing it, or bypassing it.

So, how do I tell if it's working or not?

Regards,
Ray L.

[marvinstockman]

Ray, you don't have enough R134a in the system. Listen to George.

Follow the link to a chart for static, engine and AC off pressures:

https://handypdf.com/doc/f7c181629c8...dd7b4e236a7369

Best time to do this is in the morning after the car has sat overnight.

Remember, adding too much freon is worse than adding too little.

[RayLivingston]

Originally Posted by marvinstockman

Ray, you don't have enough R134a in the system. Listen to George.

Follow the link to a chart for static, engine and AC off pressures:

https://handypdf.com/doc/f7c181629c8...dd7b4e236a7369

Best time to do this is in the morning after the car has sat overnight.

Remember, adding too much freon is worse than adding too little.

That link does not work...

What SHOULD the pressure be? Because, like I said, it's been working fine for years like this. Always blew icy cold on the hottest days.

And how do you get more to go in? When I hook up the little can, the pressure does not change. When I replaced the condenser and dryer 3 years ago, I pumped down the whole system, and put new refrigerant in, and ~30-35 PSI was all I could ever get on the low side. That was well less than two cans. But it worked fine. So what SHOULD it be, and HOW do I get it to take more?

Regards,
Ray L.

[RayLivingston]

I should point out I am also well above sea level - about 2800 feet, so ambient pressure is lower. And, temperature here is a bit cool - no more than 60F. Every chart I can find indicates under these conditions, low-side pressure for an R143a system should be 25-35PSI, which is exactly where I am.

If pressure IS low, then there has to be a leak, as it's been working fine for years. So, before adding more refrigerant, perhaps I should do a leak test. No point wasting expensive refrigerant if it's just going to leak out.

How to do leak test? UV dye? What about the electronic "sniffers"? Do they really work? Are they good enough to find what must be a fairly small leak?

Regards,
Ray L.

[gbalthrop]

Originally Posted by RayLivingston

... Noise - the noise sounded to me more like a noisy expansion valve... Turning the "snowflake" switch on and off would make the noise start and stop... Fans work fine, and make normal noise. Also there was NO audible noise in the engine bay with the snowflake on or off...
Compressor - So it's normal for the center part of the compressor pulley to be stationary when the engine is running? [NOT if it is "Compressor Valve" model with NO clutch; see below]
Fuses - Don't recall when this car was built, [see Build Month/Year on sticker at bottom of Driver Door opening, B-Pillar, and let us know if NOT <2/2007]...
Climate Control Panel - All functions operate 100% normally, except there is no cold air.
Pressures - I clearly remember when I charged this system, several years ago, ending up with ~35 PSI low-side pressure - could not get it any higher. high side was, IIRC, ~160PSI. [See Below]...
I was looking earlier for the pressure switch. It appears to me to be located on the driver side, perhaps alongside the air filter box? I assume it should be closed with there is enough pressure, and can be tested with a continuity tester?...
High-side pressure is the same a low-side pressure - 35PSI, engine on or off. My high-side pressure gauge was stuck on 0. I gave it a whack, and it started behaving.
Compressor is spinning. I was looking at the wrong thing. This being a 335i, there is so much in the way it is impossible to see the compressor itself, and only barely possible to see a little bit of the pulley. But I can see the center bolt on the compressor shaft, and it is spinning when the engine is running...
OK, so I found the pressure sensor (sensor, not switch), just behind the coolant overflow tank, under a heat shield. Since it appears to be an electronic sensor, rather than a simple switch, I see no way of testing it, or bypassing it. [INPA, see below]...
What SHOULD the pressure be? [It depends, see what I wrote in prior post & see below ]
And how do you get more to go in? When I hook up the little can, the pressure down not change. When I replaced the condenser and dryer 3 years ago, I pumped down the whole system, and put new refrigerant in, and ~30-35 PSI was all I could ever get on the low side. That was well less than two cans. But it worked fine. So what SHOULD it be, and HOW do I get it to take more?...

Hi Ray,

YOU can Diagnose this with help of the Forum and your Gauges, so pretend it's someone else's car you're working on & relax.

NOISE:
Only noise I've ever heard an expansion valve make is a "hissing/ringing" noise, usually when the system is low on Refrigerant (R-134a).

COMPRESSOR TYPE -- CLUTCH OR NOT:
Do I understand correctly that you NOW are looking at the Compressor, and NOT the alternator, P/S Pump, etc., AND the entire center section WITHIN the pulley belt grooves is ALWAYS turning, regardless of whether the Snowflake is LIT or NOT, or A/C system is ON or OFF? THAT is the way the "Clutch-less" "Compressor Valve" model of the compressor functions. ALSO, if it had a clutch, you would see wires for clutch activation running over the top of compressor to behind the pulley, as shown in this TIS video, the compressor on RIGHT of screen:
https://www.newtis.info/tisv2/a/en/e...eos/1VnY9cKgnR
We need to at least get clarity on WHICH compressor you have.

SYSTEM PRESSURE:
A) Static Pressure, or "Equilibrium Pressure": There are several ways/modes of reading system pressure. The FIRST thing to check is WHAT pressure there is on High Side when system is OFF, and has BEEN OFF for several hours. The compressor is NOT pumping Refrigerant (R-134a), and BOTH High & Low side port pressure (both Manifold Gauges) should read the same. Even Static Pressure varies with Ambient temperature, as the Refrigerant expands and has a higher "Vapor Pressure" as Ambient Temp increases.

I just rechecked my system this evening, engine OFF, when ambient temp was 67F and the engine/ compressor had not been run for ~ 8 hours. INPA showed Refrigerant Pressure Sensor Value of 5.5 bar, and Manifold Gauge connected to High side ONLY showed 83 PSIG. Conversion of 5.5 bar to PSIG computes 79.77 PSIG, so close enough for this purpose. My A/C operates & cools properly at that value, although it may be just a bit low on Refrigerant, as the Evaporator Temp doesn't get quite as low as it should. Remember, that is STATIC pressure, with Engine OFF and has BEEN OFF for > 8 hours. Under those conditions BOTH High Side & Low Side Pressures should be SAME, but what we are concerned with is WHY your compressor is NOT pumping, whether due to LOW Refrigerant Pressure, Bad Pressure Sensor, or Faulty Compressor.

You indicate your High & Low side pressures are the SAME, ~ 35 PSIG with engine OFF. You do NOT indicate WHAT Ambient Temp is, but I assume if you're in CA, it's at least in the 60's if NOT 70's. 35PSIG at the Refrigerant Pressure Sensor on the High Side line on top of the frame rail, located between the Coolant Reservoir and Washer Filler Tube is probably NOT enough for the IHKA/JBE to activate the Compressor Valve. The PROOF is in the Low Side pressure being as HIGH as the High Side Pressure, whether engine is running or not, Snowflake LIT or NOT. The Compressor is NOT pumping.

III. Adding R-134a:
I have never added any refrigerant to my 328xi system. HOWEVER, I have done all my own refrigeration system work for 50 years, and never had an issue with 12-oz cans NOT being able to charge the system. Even after pumping out the system, simply attaching the Can/Can Tap to the Low Side Port has always gotten enough refrigerant into the system to engage the Compressor. If the system was completely empty, at least a PART of a 2nd 12-oz can is needed to get a full charge and proper gauge readings. If "Can Pressure" were NOT enough to get sufficient refrigerant into the system for the Pressure Switch to engage clutch or activate Compressor Valve, HOW would one ever "inject" enough refrigerant to get the compressor to run to "pump in" MORE?

IV. Charging by Gauges:
There is NO way to know "For Sure" how much refrigerant is IN your system NOW (measured by WEIGHT, which is the only absolutely safe way to measure). If you read the label under the hood, it indicates what the TOTAL refrigerant charge should be, BY WEIGHT. My 2007 328xi says "590 grams, 20.812 oz." So that is ONE FULL 12-oz can and 73% of a 2nd 12-oz can.
There is probably a way that one could reliably calculate the weight of refrigerant LEFT in your system if he had the proper information about total system Volume (space in empty system), R-134a vapor pressure charts at different ambient temps, etc. Since only a few "Chemical Engineers" or such have that information or know how to use it, the rest of us would have to evacuate the system and recharge by weight.
Personally, I have NEVER had an issue with charging my own A/C systems just using a Temperature/Pressure chart to SLOWLY bring the High Side UP, and Low Side Down to essentially the MIDDLE of the range shown in a chart such as the one linked below:
http://acprocold.com/faq/r-134a-system-pressure-chart/
https://www.autozone.com/diy/climate...echarge-car-ac
Those charts don't mention the need to have AIR FLOW across BOTH the Condenser (Radiator Fan running) AND Evaporator (Blower Fan Running), but otherwise, look like something you could safely charge by with the following caveat.

As long as you know how much Refrigerant it would take to charge an empty system, and don't keep adding AFTER you get within range for BOTH High & Low Side Pressures, it would take something very STRANGE to actually OVER-charge the system, and I have never experienced such a thing.

If you have a Windows Laptop, I would suggest getting BimmerGeeks K+DCAN cable for $45 and FREE BMW Standard Tools (includes INPA) download from MEGA site linked on BimmerGeeks "Downloads" page, along with E89 Datens. You can then SEE what value the Refrigerant Pressure Sensor is reporting to the JBE/IHKA Modules. You can also see Evaporator Temp, Flap Positions, and all the other INPUT values to IHKA/JBE that you need to diagnose an A/C issue. Absent INPA or other BMW-specific Scan Tool or Software to read that INPUT/Value, I do NOT know of any way to test the Sensor. It IS a Sensor (NOT just a switch), capable of showing changing values as the High Side Pressure increases with Compressor Pumping, so I presume it is similar in function to a thermistor which has changing Resistance (Ohms) with changing Temperature (Pressure for this Sensor). I have approximate temp/resistance values for temp sensors, but NOTHING for this pressure sensor.

SUMMARY:
You need A/C. Your's is NOT working. Summer is coming. You need a "Plan":

1) Plan A (Safe & gives Future Diagnostic Capability): Download/Install INPA & check back for specific "How To" instructions on reading Live Data.

2) Plan B (Safe, but requires purchase of Vacuum Pump if you don't have one): Evacuate system and recharge with EXACT WEIGHT of refrigerant specified for YOUR model. HOWEVER, if compressor still does NOT run after recharge, you have wasted your time, as either the Refrigerant Pressure Sensor, its wiring/ connector, or the compressor itself is NOT functioning, and likely requires replacement, so you have to (i) guess which of above; (ii) get proper diagnosis with INPA or similar; and/or (iii) Open system (losing all new refrigerant) and replace Sensor OR Compressor.

3) Plan C (Stands for CHOOSE this one ;-): ADD a can of R-134a, SLOWLY, to your system through the Low Side port (Engine OFF), as you monitor the High Side port pressure with Red Gauge attached. If High Side pressure reaches 90 PSIG, quit adding refrigerant (it probably will NOT get near that with a 12-oz can). NOTE/Record High Side Pressure after adding 12-oz can. Connect Low Side Gauge (High Side Gauge remains connected), and RECORD pressure of Low Side, which should be ~ Same as High side until engine is started. Start engine, activate Compressor Valve (Snowflake button), and NOTE gauge pressures & ambient temp, shutting down engine if pressures do NOT change, or if EITHER pressure is HIGHER than the Chart Value for Ambient Temp.

If your Equilibrium/Static Pressure (Engine OFF) is 35PSIG on BOTH High/Low Sides now, your system is GROSSLY undercharged, and I see no way adding 12 oz of R-134a to a system that is designed for 20.8 oz total charge is going to damage anything. If you add SLOWLY with High Side gauge measuring system pressure, and do NOT exceed 90 PSIG (Engine still OFF & Ambient Temp ~ 70F), I can't imagine how that will damage anything.

Please let us know what you find,
George

[RayLivingston]

George,

I think you've highlighted the flaw in my logic - I clearly recall seeing ~35 PSI pressure when I replaced the condenser ~3 years ago. But that would have been with the engine on, AC running. Now I see the static pressure, on both high and low sides, when the system is off and stabilized, should be MUCH higher. I was not expecting that, but it now makes sense. So, I now see you are right, my system must have lost pressure over the last couple of months. Given that it has worked fine for the last 3 years, I have to conclude there is now a leak somewhere. So, first order of business has to be to find and fix that leak, before wasting any more refrigerant by topping it off now. I have a vacuum pump, so no problems properly evacuating the system after repairing whatever is leaking.

BTW - ambient temp here is 55-60F lately.

I also accept that I must have a clutchless compressor. AFAICT, ALL E90s have clutchless compressors.

So, the question now is: How to find the leak? This is something I've never had to do. I can see two common methods - UV dye, or an electronic "sniffer". Both seem straight-forward, but both have their advantages and disadvantages.

The dye sounds messy, and I assume the whole system would need to be flushed and refilled to remove the dye once the leak is located, no?

The sniffer sounds convenient, but seems to me may likely not locate the leak as precisely as the dye would, and I would be concerned about the difficulty of even reaching many of the points that would need to be checked. This is a 335i, so you cannot even SEE the compressor without removing a bunch of stuff, particularly the airbox and several of the intake ducts to/from the turbos and intercooler. There is no part of the compressor even partially visible, either above or below, much less accessible, without removing all of that. I have similar concerns about the evaporator.

Do you have experience with either approach? Which do you recommend? Any tips or pointers?

Thanks again for your help.

Regards,
Ray L.

[gbalthrop]

Originally Posted by RayLivingston

... So, the question now is: How to find the leak? [I have had good luck with UV Dye -- see below] The dye sounds messy, and I assume the whole system would need to be flushed and refilled to remove the dye once the leak is located, no? [NO, see below]
The sniffer sounds convenient, [so IF the sniffer detects refrigerant coming from a facia vent, does THAT mean the Evaporator is LEAKING? What about leak under the hood with air being drawn through the Microfilter into the Blower? I've seen pro's make gross errors with "sniffers" particularly when first used widely in early 90's.] but seems to me may likely not locate the leak as precisely as the dye would [KEEP that thought ]...

I would suggest getting a 12-oz can of R-134a containing UV Dye, and a kit that contains Blacklight & UV Glasses. Here are examples of BOTH for less than $35. I have used the "A/C Pro" UV Kit for years, and there is NO reason to pay $MORE$:
https://www.amazon.com/Interdynamics...NsaWNrPXRydWU=
https://www.amazon.com/Chemours-R134...269408&sr=8-12

You do NOT need to evacuate the system to add the R-134a that includes the UV dye. Since your system is already nearly empty (~2 bar system pressure), You can serve TWO functions at once:
1) Charge your system (as described in prior post) to test Refrigerant Pressure Sensor & Compressor Function, and be able to look for leaks if/when Refrigerant Pressure/ charge is lost. MOST leaks are at o-rings at fittings, which are usually in spots you can visualize without dismantling the entire car, such as the High/Low side port Schrader valves, where hoses attach to components, the Pressure Sensor, the Condenser coil face (stone damage).

I don't know how well an endoscope (~ $20 for USB scope to connect to your laptop) would do inspecting the Evaporator coil, or Compressor fittings, but I would try that if I had a leak that was NOT in an obvious spot. "Seeing is believing" -- sniffing works for dogs.

With that Refrigerant Pressure Sensor in a "High-heat" area over the turbo's, I would inspect that with UV light FIRST after recharging with dye. As you note, if you had to replace ANY component, even an O-Ring or Schrader Valve, in the refrigeration lines, then would need to open the system which means discharging or pumping out the refrigerant. Although you don't want to spray dye all over (makes future leak testing problematic ;-) there ARE ways you could do that yourself. DJT might even send you a commendation for being a "Bad-Ass Scofflaw" instead of reporting you to the EPA (Are they still in business?) for Clean Air Act violation.

I'm NOT aware of any reason leaving the dye charge in the system can cause damage. My 32-year-old Jag XJ-S has had dye in the system for years, with NO issues. UNLESS there is a reasonable theory of dye causing damage to something in the system, then if it leaks again, you ALREADY have your evidence -- just inspect with "blacklight" & glasses.

George

[RayLivingston]

George,

I'll be doing exactly what you suggested. After doing some research, I decided dye was the better way to go, so I will put some in, check for leaks, and fix anything I find. Then I will probably evacuate the whole system and re-fill, to make sure it has the proper charge.

It'll be a few days before I have time to do ti all, but I'll report back when I know more.

Just for grins, I put the gauges on my E46, and found it had about 55 PSI on both sides after sitting over-night.

Thanks again for your help.

Regards,
Ray L.

[krob]

Ive got similar issues, I evacuated the system, added new 134a and Pag Oil, pressurized to proper levels, but my problem is that my evporator temp is 60F ish. Not nearly what it should be. System is holding pressure, Could this be a clogged expansion valve? System circulation is low?

[RayLivingston]

If your expansion valve is clogged, you should be getting wonky pressures, like very low high-side pressure. With engine running, AC on MAX, what pressures do you see?

Regards,
Ray L.

[mweisdorfer]

Originally Posted by RayLivingston

I have an '07 335i. Due to the Corona virus lockdown here in the SF Bay area, we had not driven for 6-7 weeks, until yesterday. All is well, except the AC is totally kaput. It was, briefly, making a strange screeching noise that sounded like it was coming from somewhere in the center console, but that has gone away. Near as I can tell, the AC clutch is never engaging. When I look down the front of the engine with the engine idling, the front of the compressor clutch is NOT spinning.

The climate control panel operates normally. Both fuses associated with the "snowflake" icon (fuses #29 and #60) are fine. There is pressure in the system, about 30PSI static on the low side with engine off. I seem to recall when I topped off the system about 3 years ago that is where it ended up.

When I start then engine, the high side pressure jumps up just very slightly off the bottom of the gauge, I'm guessing to about the same pressure as the low side, then just stays there. Never goes any higher.

Pressing the A/C "snowflake" switch has no visible effect on the compressor, so it appears the clutch has either completely failed, or there is a fault somewhere preventing it from ever being engaged.

I assume there is a low pressure switch somewhere that could cause this. Where is it?

What else should I be looking at/for?

Regards,
Ray L.

What codes are you getting?

[RayLivingston]

I finally got into town to buy some R134 with dye, but the result just leaved me more confused that ever. I hooked up the gauges and the can of dye. It sloooowly got sucked in, and the pressures started coming up. Both sides started at about 30 PSI. After perhaps 10 minutes, both sides got up to the high 30s, and the high-side then rather quickly (over just a few seconds) shot up to about 75PSI. After a few seconds, there was a loud hissing sound that seemed to be coming from somewhere near the front exhaust side of the engine bay, and the pressures both dropped very quickly - the low side dropped to something like 15 PSI, and the high-side dropped back down to the low 30s.

Now here's the really weird part - I can see no hint of dye anywhere. I have a 60W UV light, so the slightest hint of dye lights up so bright a blind man could see it. The only explanation I can come up with is the dye had not circulated around to that part of the system yet. I would guess (based on weight) it had sucked in perhaps one quarter to one third of the can of dyed refrigerant by the time the hiss appeared.

I repeated the test a second time, with exactly the same result. So, there seems to be something that is acting like a pressure relief valve that is blowing off somewhere. What on earth could that be? And where? And why is there NO dye showing up anywhere?

Regards,
Ray L.

[RayLivingston]

Well, this is a comedy of errors, minus the comedy. The hiss was due to a fitting on my gauge set that had come slightly loose, preventing the high-side hose from locking onto the fitting properly. My guess is it was sealing enough to hold up to about 40 PSI, then blowing off after that. I tightened the loose fitting, and got the rest of the dye, and a remains of another can of R134 in there. I believe the charge is still a bit less than adequate, but I do have 36F air coming out of the center vents.

I noticed as it was charging, which took a loooooong time, both low and high side pressures would move around quite a bit. At first, when the charge was quite low, the pressures would vary from 15-20 PSI on the low side, and 125-175PSI on the high side. They would roughly track each other - both would slowly work up to their highest readings, then they'd both slide back down to their lowest readings, on about a 3 minute cycle. As the charge got closer to spec, the range of variation on both decreased dramatically. The low side now varies, slowly, between 27-30PSI (60F ambient), while the high side ranges around 150-165PSI. I assume this is normal?

I have no more refrigerant on-hand, but the system is working ok for the time being. I will drive it like this for a few days, monitor the pressures, and periodically use the UV light to check for leaks. After a week or two, if all seems ok, I'll evacuate the whole system, and re-charge it from scratch, to get the correct charge in there.

Regards,
Ray L.