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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 > AC not cold (INPA screenshots inc.)



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      07-03-2018, 06:31 AM   #1
stashio
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Cool AC not cold (INPA screenshots inc.)

To coincide with the heatwave we're having the UK my AC has decided it doesn't want to blow cold/cool air anymore. At first I thought it was the refrigerant and so took it to a specialist to have it refilled, the guy said it was a little low but not empty but I had him recharge it just in case. It didn't fix it. I've read around the forums and checked the usual things, blower motor works, fuses (15 and 61 on mine) are fine. I read somewhere someone fixed it by installing new IHKA software, mine was already up to date but I did it anyway - no luck, still no AC.

I got INPA going, no error messages at all but did notice the evaporator wasn't getting cold - could that be a sign of broken compressor or evaporator? Screenshots below if they're useful, any suggestions? Thanks.






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      07-03-2018, 03:35 PM   #2
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Anyone? I know there's a few AC posts around at the moment but I've gone through those already. We're in the middle of a heatwave
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      07-03-2018, 03:47 PM   #3
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First off, it's great that you've already checked the common failure points AND posted all this raw data.

When you enable your AC, can you hear/feel the compressor going to work? Our compressors are clutchless, but the nature of their variable-displacement design is such that you can usually feel them 'kick in.' This is where I'd start. If you feel nothing, then I'd say that's a good indication of compressor issues. If you're unsure, you could try using a suitable pressure gauge for diagnosing whether the compressor is cycling.

I wish I could help more.
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      07-03-2018, 11:26 PM   #4
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Quote:
Originally Posted by stashio View Post
...my AC has decided it doesn't want to blow cold/cool air anymore...I got INPA going, no error messages at all but did notice the evaporator wasn't getting cold - could that be a sign of broken compressor or evaporator? Screenshots below if they're useful, any suggestions? Thanks.
I assume (if you have the IHKA system) that you have pressed "MAX" in the Driver-side Thermostat switch, or set both Driver & Passenger Thermostats to 60F/34C (that is what the INPA readout suggests) and Compressor "Snowflake" green indicator is lit. My take from your data is that the Compressor Valve is NOT opening. I would check (engine off & cool so fan does NOT run) to make sure that connector to compressor is clean, wiring intact, and correctly attached. If so, then check wiring between JBE & Compressor Connector.

It appears that the IHKA Module (via JBE module) is reading the Refrigerant Pressure Sensor output (8.5 bar), but that the Compressor Valve is NOT opening. Ask someone who really knows INPA what "Y-Value" or "Y-Wert" means. My SWAG is that it is either the signal to or from the Compressor Valve that determines how much it is supposed to be (or is) open, and in your case, the "Y-Value" is as low as it can get, which would explain system pressure, but NO cooling of the Evaporator. See the TIS circuit diagram for the Compressor Valve (Y2a)for the N55 335i E93:
https://www.newtis.info/tisv2/a/en/e...ution/CkVAsJaJ

The definitive way to determine compressor function is to put manifold gauges on the High Side and Low Side quick connectors with engine off. If engine is off and the compressor has NOT been pumping refrigerant recently, the system will be "at equilibrium" and BOTH High Side and Low Side gauge readings will be ~ the same (~ 8.5 bar = 123 PSIG per your INPA data). Then, if you start the engine, press MAX button and gauges STILL remain the same, or nearly so, they you KNOW the Compressor Valve is NOT opening, and NO refrigerant pumping is taking place.

Didn't the shop that recharged your system DO THAT???

Your INPA data screenprints are VERY helpful diagnostics.
1) Even when outside ambient temp was only 19C = 66F, the Evaporator Temp was 34C = 93F, which is warmer than any vent temp (footwell, etc.).
2) Refrigerant Pressure (That would be the CORRECT translation of "Druck Kaltemittel" instead of 'Print Cooling agent' for the 4th Analog bar graph in the 1st column) is 8.5 bar = 123 PSIG. That is certainly enough R-134a system pressure to allow the Compressor Valve to open and have the compressor pumping the refrigerant to cool the Evaporator, BUT it appears the Compressor Valve is NOT opening.
3) Check with someone who knows what Y-Value means in INPA, but on my 328xi, with compressor functioning, and Evaporator temp ~ 9C, my Y-Value is ~ 41, or 65% of way from min to max on the bar graph. As stated above, my best guess is your "Min Y-Value" indicates Compressor Valve (Y2a) is NOT opening.
4) I'm ignoring flap positions, since the critical thing is the Evaporator Temp reading, which is consistent with NO cooling from vents, and the min Y-Value.

Please let us know what you find,
George
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      07-04-2018, 09:48 AM   #5
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Y-Value???

Quote:
Originally Posted by gbalthrop View Post
...Ask someone who really knows INPA what "Y-Value" or "Y-Wert" means. My SWAG is that it is either the signal to or from the Compressor Valve that determines how much it is supposed to be (or is) open, and in your case, the "Y-Value" is as low as it can get
Hooked up INPA to my 328xi today, and I could NOT determine ANY relationship between Y-Value reading and whether the Compressor Valve cutoff (snowflake) was pressed/lit or not. Bottom line, is I do NOT know what "Y-Value" is supposed to represent. ANYONE who does know, please enlighten us.

In ANY event, on my properly functioning IHKA system, I have NEVER seen that bar graph at anything less than ~ 25% of way from min to max (-130 to +130), so in your case, with Y-Value at -128 (1% or less of range), that would appear to be significant (if we only knew what it meant ;-)

George
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      07-04-2018, 09:59 AM   #6
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The shop charged the system and couldn't look at the pressure gauges while the system is running to determine what is wrong... wow. Purchase a high and low pressure gauge and google R134a pressure temp chart to give you an idea of where they are. The pressures will indicate what component is not working or if you have a blockage, you can google pressure readings interpretation and that gives you possible causes: ie failed expansion valve, etc. If your pressures are good, that means you don't have a leak which is a good thing because replacing an evaporator is a pain in the ass.
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      07-04-2018, 03:16 PM   #7
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Wow! Thanks for the wonderful contributions so far I genuinely appreciate it. I'm working away at the moment but will be home Friday so brace yourselves for more then
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      07-04-2018, 03:51 PM   #8
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Quote:
Originally Posted by stashio View Post
Anyone? I know there's a few AC posts around at the moment but I've gone through those already. We're in the middle of a heatwave
There is a DIY video on YouTube for AC.

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      07-05-2018, 07:52 AM   #9
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I had a quick look on TIS and wonder if the Y-value is this:
https://www.newtis.info/tisv2/a/en/e...i-cab/HnocbPkO

which looks like the control valve for the compressor. That's a complete guess going off nothing else but the name of valve being Y2b.

Anyway I'll be home tomorrow so will inspect connectors, wires, etc... and let you guys know.

PS thanks for the youtube link, typically it's blocked at work but I'll have a look when I back home.

EDIT: George had already posted about the Y value in his first post - that'll teach me for speed reading!

Last edited by stashio; 07-05-2018 at 08:03 AM..
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      07-05-2018, 07:55 AM   #10
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Quote:
Originally Posted by mecheng77 View Post
The shop charged the system and couldn't look at the pressure gauges while the system is running to determine what is wrong... wow. Purchase a high and low pressure gauge and google R134a pressure temp chart to give you an idea of where they are. The pressures will indicate what component is not working or if you have a blockage, you can google pressure readings interpretation and that gives you possible causes: ie failed expansion valve, etc. If your pressures are good, that means you don't have a leak which is a good thing because replacing an evaporator is a pain in the ass.
Yeah it was done at a UK chain called ATS - they're not known for going the extra mile unless you're luckily enough to get a helpful technician. I've got a replacement interior to fit (mine is grey which I don't like at all) so wanted to rule out the expansion before swapping the interior as I'd heard you had to remove a lot of it anyway to replace the expansion.
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      07-05-2018, 08:01 AM   #11
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Quote:
Originally Posted by gbalthrop View Post
Hooked up INPA to my 328xi today, and I could NOT determine ANY relationship between Y-Value reading and whether the Compressor Valve cutoff (snowflake) was pressed/lit or not. Bottom line, is I do NOT know what "Y-Value" is supposed to represent. ANYONE who does know, please enlighten us.

In ANY event, on my properly functioning IHKA system, I have NEVER seen that bar graph at anything less than ~ 25% of way from min to max (-130 to +130), so in your case, with Y-Value at -128 (1% or less of range), that would appear to be significant (if we only knew what it meant ;-)

George
Thanks for taking the time George I really appreciate it. I think you're right about the Y-value, the fact it's completely zero looks really strange. Hopefully it's a connector or something - I'll look into it tomorrow and report back.
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      07-05-2018, 05:10 PM   #12
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Quote:
Originally Posted by stashio View Post
...Y-value, the fact it's completely zero looks really strange. Hopefully it's a connector or something - I'll look into it tomorrow and report back.
I couldn't find anything Googling y-value, BMW y-value, INPA y-value, etc. other than the general math concept of x & y coordinates related to slope of line, etc. and a measure of heat loss in building HVAC applications.

Rather than focus on what we do NOT know (what Y-Value means in INPA), I suggest focusing on what we DO KNOW:
1) with engine running, High Side pressure is 123 PSIG (8.5 bar) which is enough to support safe compressor operation, yet
2) Evaporator Temp is greater than ambient temp (apparently from car sitting in sun and elevated interior temp) and High Side pressure is LESS than it should be if compressor were "pumping" with Compressor Valve active.

So that suggests the compressor is NOT pumping (valve NOT active) and the JBE is getting sufficient pressure signal from Refrigerant Pressure Sensor to activate the Compressor Valve. As suggested earlier, I would simply take the old-school approach, and with a cold engine (not run for 3 or 4 hours):

1) attach manifold gauges to the High Side and Low Side ports;
2) record readings; attach INPA with Analog screen active that shows Evaporator Temp & Refrigerant Pressure (Print Cooling agent ;-)
3) press MAX button on A/C thermostat;
4) start engine and make sure green LED lit on compressor cutoff button (snowflake), as well as MAX button, blower inside is running at max speed, and thermostat displays each show 60F/ 16C.
5) watch/record manifold gauge readings, and correlate High Side gauge reading with INPA Refrigerant Pressure readout.

The High Side pressure should of course go UP, and the Low Side pressure should go DOWN with compressor valve active. There should be a significant difference/ delta between the High & Low side pressures -- something along the lines of 200 PSIG vs. 50 PSIG at a minimum.

If the High Side goes too high, that suggests a blockage in the expansion valve, and the Pressure Sensor should deactivate the compressor valve to protect the compressor (too high a pressure reading at the Refrigerant Pressure Sensor ~ 300PSIG or more). Rather than ASSume that the INPA Refrigerant Pressure Sensor readout is correct, make sure you correlate that with the High Side gauge pressure.

As stated before, I can't imagine a reputable shop charging your system and NOT attaching gauges to note such pressure differential, and also putting a thermometer on the dash vents to determine that you were getting compressor function and refrigeration. Until ~ the last decade there were no built-in Evaporator temp sensors to get readout from, and AFAIK that is still true today for most vehicles.

The only thing that is really different in the BMW refrigeration cycle from refrigeration systems 40 years ago is the compressor valve vs. compressor clutch. As well-engineered as BMW electrical/electronics systems are generally, I have to believe they have some capability in INPA/ISTA to monitor compressor valve operation, and we are just missing it.

Perhaps I'm still thinking too much like an on/off clutch effect, and missed something significant in the INPA readout when I pressed the snowflake to turn OFF the compressor function (via the valve). The interior quickly got warmer and the Evaporator Temp readout went up, but I saw NOTHING in the Analog readouts that appeared to be directly related to Compressor Valve function. Now if you go to Control Unit Buttons (F3) and check to see if the circle fills/blanks for the A/C Compressor when you push the snowflake button, that at least will tell you about IHKA control panel button function, but I don't imagine it will tell you if the compressor (a) received the signal, or (b) the Compressor Valve changed function.

Hope you learn enough to educate the rest of us very soon,
George
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      07-05-2018, 05:26 PM   #13
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I have this problem too but I live in Canada so meh lol
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      07-06-2018, 12:16 PM   #14
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Cheers George!

I had a look at the connections, they're secure but I couldn't unplug the compressor plug to clean, didn't want to risk it breaking.

I stripped some insulation off both wires going to the valve and applied power/earth as appropriate but didn't make any difference. I wonder whether there's a way to manually run the compressor.

Good point on the manifold pressures, I guess I'm hoping to rule the quick/easy issues first but I'm running out of alternatives!
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      07-06-2018, 12:17 PM   #15
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Quote:
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I have this problem too but I live in Canada so meh lol
Lucky you
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      07-07-2018, 04:11 AM   #16
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I checked the panel output in INPA and can see the buttons responding to pressing so that all works fine, nothing to show the response back from the compressor unfortunately. I'm starting to wonder whether it's the compressor itself that's broken, certainly if the y value is the valve then maybe it's stuck or something. I need to put the plastics back on this morning so will give the compressor an engineer's whack before I do.
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      07-09-2018, 05:46 AM   #17
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Well no luck with loose connections or giving the compressor a few knocks, still not working. I need to order some gauges but in the meantime I remember seeing some clear oil on my drive a few weeks ago - we'd have builders round so assumed it was from one of their vans but now I'm wondering whether it was compressor oil? Can the compressor be operated manually to check it actually works before I continue?
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      07-09-2018, 07:54 AM   #18
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Quote:
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I have this problem too but I live in Canada so meh lol
Maybe Victoria is mild, but it was 37C last week and with humidex, in the 40s. I was sweating my sack off, the A/C in the car was nice and cold, 8-10C.
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      07-09-2018, 08:21 AM   #19
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Yeah i'm in Canada but the few 30C+ days we had were brutal, my AC could not keep up at all
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      07-28-2019, 09:55 PM   #20
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I realize this is an old thread, but it looks like the problem I'm having and I'd like to know if you ever resolved this. If so, what was the problem?
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