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BMW 3-Series (E90 E92) Forum > BMW E90/E92/E93 3-series General Forums > General E90 Sedan / E91 Wagon / E92 Coupe / E93 Cabrio > Help with A/C - images included



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      07-27-2017, 05:49 PM   #1
lucius
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Question Help with A/C - images included

Hi, I'm in the process of troubleshooting my A/C issue.

Symptoms: A/C not blowing no cold air.

During the week of the June 11th, I had my A/C recharged. The A/C was somewhat cold during the time of this recent recharge, but I do recall it being much colder.
I've been noticing the A/C is not as cold as it once was when I last had it recharged. I'm suspecting a leak but am having trouble determining what specifically could be the cause of my A/C issue.

The center vents on the driver's side appears to be just a hair cooler than the passenger's side.

I've performed the following tests:
  1. Confirmed A/C compressor engages (based on small wining noise when snowflake button is pressed)
  2. Both ISTA and INPA have no IHKA fault codes
  3. INPA is reporting the evaporator pressure being 4.5 bars when A/C off and 5.0 bars with A/C on. (I'm hoping I'm reading this information correctly)
  4. ISTA is reporting the refrigerant pressure to being 7.00-/+
  5. At the time of my last recharge, UV dye leak detector was added into the low pressure side
  6. And yes, the temp dials are set to 60 degrees - INPA is reporting that both dials are set to 16



My gauges (mountain gauges) read the following while the outside temp was approx 65 degree:

This was performed with the engine running for approx 5 mins+ and A/C set to max. From my understanding the low pressure side is supposed to read with the range of 28~35 PSI

Low side: 28 - 35 psi
High side: 2x - 2.5x ambient temperature + 100

I'm a bit unclear to what range the the high pressure side needs to be in; but please feel to correct me if I'm wrong.




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I'm unable to detect any signs of leaks with my black light.









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I'm willing to re-test by adding refrigerant and cleaning the low pressure valve to make sure it's not the actual valve that could potentially be leaking shown below:


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Questions:
Is there anything else I should be checking?
How about testing the expansion valve?
Is there anyway to check the evaporator for potential leak without having to unnecessarily rip my dash out?

With the system evacuated and vacuumed, how many of those 12oz R134A cans would it take to properly fill the cooling system? From what I've gathered, it's approx 18oz. Again, please correct me if I'm wrong.

Admins / mods - please move this to the appropriate forum if this is the incorrect forum.

Any help will be appreciated.
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      07-27-2017, 09:35 PM   #2
kkasson
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Total capacity should be about 20.8 ounces, I believe. There should be a sticker under the hood with the correct amount.

The pressure readings get less and less useful as the temperature goes down; at 65 degrees it's kind of hard to use them. But the range you're looking for is approximately 25-35 psi on the low side and 135-155 psi on the high side. I've found it's hard to use the pressures in general with the E90's clutchless compressor.

What's confusing me, though, is that your gauge is reading only about 70 psi but the pressure sensor is reporting 100psi (7 bar). I'm not sure where exactly the sensor is in the system so it may be that the pressure is slightly different between where the sensor is and the high-side port is.

But in any case it seems like it is a bit low on refrigerant. When it was recharged before did you do it yourself or have a shop recharge it? Do you know how much was added then?

It's usually pretty easy to tell if it's leaking from the low pressure port; you can often see it kind of bubbling out. You don't want to look straight into it, obviously, in case it sprays out at you, but you should be able to see evidence of it in there. It's normal for it to bubble a little bit after removing the hose from it, but if it's been sitting and you see something then it might be the problem. I'd guess that's probably not the issue though.
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      07-28-2017, 11:14 AM   #3
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Quote:
Originally Posted by kkasson View Post
What's confusing me, though, is that your gauge is reading only about 70 psi but the pressure sensor is reporting 100psi (7 bar). I'm not sure where exactly the sensor is in the system so it may be that the pressure is slightly different between where the sensor is and the high-side port is.
Those readings were done one separate days, which may be the reason why the readings aren't reflecting each other. I can pull ISTA / INPA pressure values while the manifold gauges are installed to get more of a less confusing reading.

Quote:
Originally Posted by kkasson View Post
But in any case it seems like it is a bit low on refrigerant. When it was recharged before did you do it yourself or have a shop recharge it? Do you know how much was added then?
I had a shop that specializes in BMWs recharge my system. The tech used a device similar to Cool-Tech 34788



What's unknown is the amount of refrigerant I had in the system before the recharge and how much was added.

Is there a way to properly test the evaporator?
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      07-28-2017, 01:12 PM   #4
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It's probably the evaporator. That's a common issue with our cars. Mine is on its third one already. I believe it's located behind the dash. Look under there with your black light for UV-dye dribbles....

Quote:
Is there a way to properly test the evaporator?
Other than looking for the dye, what the dealer will do is hook you up to their machine, pull all the refigerant out, pull a strong vacuum on the system and see if it will hold. If not - evaporator time. If so, the machine puts your refrigerant back in and they/you need to look elsewhere for the culprit. I believe this is a $200-$300 diagnostic.
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      08-02-2017, 01:25 PM   #5
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So I found my refrigerant leak...

I would rather perform an evacuation then do a vacuum, but shops around here are charging approx $100+; even if it's just to evacuate the a/c system of refrigerant.
To make things feasible, I decided to recharge the system with refrigerant on my own since the pressure in the a/c system was decaying. I wanted to test for leaks with the system recharged.


Once my system was recharged, my a/c was blowing cold and crisp. Actually colder than ever.

I begged and prayed to the BMW gods, that my refrigerant detector didn't pick up anything near the evaporator.


Using ISTA, I triggered both the front and footwell ventilation flaps.
With the ventilation flaps opened, I used my refrigerant sniff detector and probed deep inside each vent but the sniffer detected nothing. To make sure I didn't have a faulty sniffer unit, I used the sniffer near an empty can of R134a and sure enough, it was able to detect fumes from an empty can.


I rechecked the compressor, ports, lines and all the connections and still was unable to find a leak. Only thing left to do was scrub across the condenser through the kidney grills. This was a but of a difficult process since the grills limited my movement of the wand from the sniffer.
After scrubbing the evaporator for approx 5 minutes, the detector singled a potential leak.
At first I thought it was a false positive, so I scrubbed near the area of detection. Sure enough it signaled again. I set the sniffer to low which lowers the sensitivity and it definitely picked up a refrigerant leak. The leak appeared to be in a difficult spot that I was unable to see.

I removed my front bumper to get a better view since it was difficult to see.


The leak was in the center; right in the middle. This would be difficult to see with a black light.


Here is the leak under the black light at night


I'm unsure how the condenser started leaking right in the middle. One would expect damages right behind the grills or lower portion of the bumper.

Next steps will be to evacuate the refrigerant and replace the condenser.
Once the condenser is replaced, I will pull a vacuum to ensure there are no leaks, then recharge the system.

Again, thank you all for your responses. I'm in a happy/sad mood right now because I'm so glad it's not the evaporator but I still have to dish out some money for the condenser; just not $3,500.
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      08-02-2017, 09:52 PM   #6
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Nice detective work! Glad it's not the evaporator. Even though the unit itself isn't that costly, that job is like 8 hours of labor.
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      08-03-2017, 10:33 AM   #7
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Question

I plan on pulling a vacuum after I replace my condenser. Does anyone know if compressor oil (Pag 100) is needed? If so how many ounces?
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      08-04-2017, 03:14 PM   #8
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I was able to determine how much pag oil I may need once I replace the condenser and torque specs for the condenser lines.

However, I am unable to determine if I "actually" need to add pag oil when I'm only replacing the condenser; not the compressor when majority of the oil resides. vacuum pulls air and moisture out of the system, but does it pull pag oil as well?

Please advise
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      08-05-2017, 02:44 AM   #9
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Quote:
Originally Posted by lucius View Post
I plan on pulling a vacuum after I replace my condenser. Does anyone know if compressor oil (Pag 100) is needed? If so how many ounces?
Go to following link & enter your model info; When you open TIS for your model, select Repair Manuals & Technical Data > Heating & Air Conditioning > Condenser & Dryer with Lines; also see Operating Fluids (refrigerant oil) for fluid specification:

https://www.newtis.info/tisv2/a/en/

BMW specifies an amount of oil to add for each component replaced, and ALSO specifies a SWAG amount based upon how much refrigerant was lost over a specific period of time since last system service (see table in TIS). Also, don't forget the desiccant.

George
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      08-06-2017, 03:26 PM   #10
lucius
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Quote:
Originally Posted by gbalthrop View Post
Go to following link & enter your model info; When you open TIS for your model, select Repair Manuals & Technical Data > Heating & Air Conditioning > Condenser & Dryer with Lines; also see Operating Fluids (refrigerant oil) for fluid specification:

https://www.newtis.info/tisv2/a/en/

BMW specifies an amount of oil to add for each component replaced, and ALSO specifies a SWAG amount based upon how much refrigerant was lost over a specific period of time since last system service (see table in TIS). Also, don't forget the desiccant.

George
Thank you so much for this.
I rcv my condenser tomorrow. Unfortunately I won't be able to install it til next weekend. I'll post updates.
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      08-07-2017, 08:17 AM   #11
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The condenser in my E36 was replaced under warranty for the same type of leak.
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