[Atx328]

So about twice a month, I will jump in my car and head off to my destination but the AC won't engage for 3 to 10 mins. It doesn't do it often enough that I can see any predictable pattern or circumstances.

When it does happen, the fan will still blow and I don't get any error message, but the compressor simply doesn't engage and of course the air doesn't get cool. I have tried shutting the car off and restarting, but I am not convinced that makes any difference.

Could this be caused with something as simple as low refrigerant?

If that might be the cure, I am tempted to just pop over to my FLAPS and pick up a bit of cool gas to top off. But if someone else has experienced a similar problem with a more complex remedy, I will plan to try to stop by a shop to have the pros look it over.

Once it does start working, it seems to cool down quickly. You would notice pretty soon if it didn't work because its usually 90+ and thick humidity in Central TX during the summer.

It isn't that big of deal when I am driving solo but it gets more inconvenient driving family member or co-workers.

[gbalthrop]

Originally Posted by Atx328

So about twice a month, I will jump in my car and head off to my destination but the AC won't engage for 3 to 10 mins. It doesn't do it often enough that I can see any predictable pattern or circumstances. [Look for a relationship to "underhood temperature" -- the Refrigerant Pressure Sensor that cuts out the Compressor Valve if High Side pressure is too low is located in the High Pressure line from the Condenser to the Expansion Valve, about midway & near the Exhaust Manifold. Adiabatic relationship between Pressure & Temp & all that ]

When it does happen, the fan will still blow and I don't get any error message, but the compressor simply doesn't engage and of course the air doesn't get cool. I have tried shutting the car off and restarting, but I am not convinced that makes any difference. Could this be caused with something as simple as low refrigerant?...Once it does start working, it seems to cool down quickly...

Obviously it COULD be either low refrigerant charge, or a loose wire related to the Compressor Valve Activation (Y2b) per this TIS circuit:
https://www.newtis.info/tisv2/a/en/e...bution/uZS1ONq

When you say "I don't get any error message" I presume you mean NO error message on the CID or display, and NOT that you don't have any Fault Codes saved in the IHKA (A/C Control Module) or JBE (Junction Box Electronics Module) to which the Refrigerant Pressure Sensor is attached?

If you had INPA (BMW diagnostic Software in BMW Standard Tools) it would enhance the likelihood of diagnosing the issue. I would NOT recommend just randomly adding R-134a refrigerant without proper gauge readings and knowledge, for fear of overcharge. If you could get a system pressure reading at rest and in equilibrium (engine not run for > 5 hours and low side reading > 5 Bar or Atmospheres), that would be helpful.

Is the Green LED on the "Snowflake" button on right center of A/C Control Panel lit at ALL times, or does it ONLY come on just before you feel it getting cold?

When you say "the compressor simply doesn't engage" is that based simply upon air temperature at the vents, or something determined otherwise?

Please let us know a bit more, including IF you have A/C manifold gauges and Can Tap, or Tap with Low-side gauge ONLY, also if you have multimeter and ability to test wiring from Y2b and the three intervening XConnectors to the JBE, Connector X14270. For that matter, there could be an intermittent connection between the Refrigerant Pressure Sensor, B8 and Connector X14271 at the JBE. WHATEVER is happening, it appears the Refrigerant Sensor signal is NOT sufficient to activate the Compressor Valve, or the signal from the JBE to the Valve is intermittent.

Bottom line is that if it ALWAYS decides to run when the engine compartment becomes warmer, that sounds MORE like pressure than an electrical fault, although the Pressure Sensor itself could be faulty.

Keep in Mind that INPA can quickly and easily read the pressure signal being sent by that Sensor, LIVE Data. Only problem is, if this ONLY occurs once or twice a MONTH, you would learn NOTHING from reading live data when normal operation is occurring. That's why you need INPA or ISTA to read Fault Codes in ALL Modules, particularly IHKA & JBE/JBBF.

Please let us know what you find,
George

[Atx328]

No error messages based on indicated dashboard codes or iCarly Scan.

I do have INPA loaded up but I haven't used it before. This might be a good time to dip my toe into the data.

The compressor light is indicating on but during the times that it isn't working, I say the compressor isn't working because the air stays warm and I don't "feel" the pull on the engine or the minor sound/vibration of a the compressor engaging.

I don't have any manifold gauges outside of the simple gauge that fits to the top of the recharge can. I assume that is most likely not accurate or a good idea to use for diagnostics.

[gbalthrop]

Originally Posted by Atx328

...
I do have INPA loaded up but I haven't used it before. This might be a good time to dip my toe into the data...I don't have any manifold gauges outside of the simple gauge that fits to the top of the recharge can. I assume that is most likely not accurate or a good idea to use for diagnostics.

If you're willing to take about 30 minutes to learn how to use INPA to read Fault Codes in ALL Modules using "Functional Jobs", please let me know, and I will provide simple instructions and screens on how to do that. That is the "First Step" to checking the "health" of your car and takes less than 5 minutes to do once you've done it. It's also a good way to make sure you have INPA properly installed, and K+DCAN cable USB port settings correct.

That probably will NOT show anything we didn't already know, and the best way to diagnose the "once-or-twice-a-month" fault if it does NOT save a fault code is to monitor Refrigerant Pressure using INPA, as well as Evaporator Temperature and Flap Positions. I can also provide info on how to do that, which you should be able to follow & perform in another 30 to 60 minutes. If your version of INPA has German techical terminology, NOT to worry as I have translated the terminology to English for the screens needed to diagnose IHKA (A/C) issues.

George

[Donethat]

I just went through this recently.
My ac would always take a while to finally blow cold air (2-8 minutes). The fan always blew air, but not always cold. The longer the car sat without driving (for days) the longer it would take to start blowing cold air. Also if caught in traffic it would randomly go back and forth blowing cooled and uncooled air. I knew it wasn’t leaking refrigerant. I took it to a friends shop a few weeks ago. He put it on the machine which vacuum with a complete system check for leaks etc. It showed I had air in the system. Problem solved. $125.

It blows cold constantly and immediately. Luckily It was something that simple.
Living in So Fla summer, you will not survive w/o ac.
Good Luck.

[ewicky]

Originally Posted by Atx328

...I say the compressor isn't working because the air stays warm and I don't "feel" the pull on the engine or the minor sound/vibration of a the compressor engaging...

FYI our compressors are clutchless style that don't create any noticeable sound/vibration/pull when engaging. They are always engaged, 24x7. The compressor vanes just vary to adjust the compression stroke of the pump from 2% for aircon off, all the way up to 100% for max AC. The HVAC system can command any point in that range. They don't pulse on and off like traditional clutch types.

[Atx328]

Originally Posted by gbalthrop

If you're willing to take about 30 minutes to learn how to use INPA to read Fault Codes in ALL Modules using "Functional Jobs", please let me know, and I will provide simple instructions and screens on how to do that. That is the "First Step" to checking the "health" of your car and takes less than 5 minutes to do once you've done it. It's also a good way to make sure you have INPA properly installed, and K+DCAN cable USB port settings correct.

That probably will NOT show anything we didn't already know, and the best way to diagnose the "once-or-twice-a-month" fault if it does NOT save a fault code is to monitor Refrigerant Pressure using INPA, as well as Evaporator Temperature and Flap Positions. I can also provide info on how to do that, which you should be able to follow & perform in another 30 to 60 minutes. If your version of INPA has German techical terminology, NOT to worry as I have translated the terminology to English for the screens needed to diagnose IHKA (A/C) issues.

George

Yes I think it was time that I got off the sidelines and started to use the free tools available. Please send me a link or pm

[Atx328]

Originally Posted by ewicky

FYI our compressors are clutchless style that don't create any noticeable sound/vibration/pull when engaging. They are always engaged, 24x7. The compressor vanes just vary to adjust the compression stroke of the pump from 2% for aircon off, all the way up to 100% for max AC. The HVAC system can command any point in that range. They don't pulse on and off like traditional clutch types.

I agree that my e90 doesn’t have that shuddering engagement moment that I know from older vehicles. But I swear you can hear/feel the load on the engine. I have a long, steep hill to drive up about 1 mile into my commute and the car definitely sounds different on the days I don’t have the ac on.

I have performed the intake vapor filter delete and I have a PE so my car is fairly communicative.

[ewicky]

Originally Posted by Atx328

I agree that my e90 doesn’t have that shuddering engagement moment that I know from older vehicles. But I swear you can hear/feel the load on the engine. I have a long, steep hill to drive up about 1 mile into my commute and the car definitely sounds different on the days I don’t have the ac on.

I have performed the intake vapor filter delete and I have a PE so my car is fairly communicative.

You're totally right. I just meant from a diagnostics standpoint, you shouldn't be relying on indicators of clutch engagement because that'll never happen.

When plowing up a hill in 6th, I think I can feel the aircon drag too. It is subtle enough that a soccer-mom definitely wouldn't know the difference. But, funny enough, my highway fuel economy doesn't seem to take a hit from running aircon. I would think if I can feel the drag then it certainly would reduce economy.

[gbalthrop]

Originally Posted by Atx328

Yes I think it was time that I got off the sidelines and started to use the free tools available. Please send me a link or pm

You stated earlier that you had already downloaded & installed INPA on your Windows 10 Laptop? If that is the case, I would suggest taking about an hour to just get comfortable with how to connect to the vehicle, open INPA, use Functional Jobs, and Save INPA screens as jpg image files, ALL as described in the attached pdf.

I am in the process of converting my Word Outline of INPA and Folders of INPA ScreenPrints into pdf's that can be used by anyone as a reference for how to use INPA for various functions. I will post a short pdf on connecting to the IHKA Module, Reading existing IHKA Fault Codes, and viewing Parameters such as Refrigerant Pressure, Evaporator Temperature, and Flap Positions. Hopefully being able to view that data will help you diagnose the issue. If you get tired of waiting for that, just go ahead and connect to the IHKA Module, and see the two screens described below per the following steps:

1) At the Script Selection Box which appears after selecting E90;
2) Down Arrow/Cursor in Left Listbox to Body/Karosserie & press Tab to navigate to Right Listbox;
3) In R Listbox, Down Arrow/cursor to Air Conditioning / Control Panel; Press Enter;
4) IHKA Main Menu should appear; press F5, Status, and Status Menu appears;
5) In Status Menu, press either F1 for Analog Ports, or F4 for Flap Positions.

I am NOT aware of anything you can do to harm your car by viewing any screens in F5 Status. I would however avoid doing anything OTHER than reading or copying screens in F6 Activations/Steuern until you have translated the warnings or "Driving Conditions" at the top of each screen, as you COULD get some unintended results if you "activated" something at the wrong time (such as with engine running). If you just avoid F6 for now, you can generally experiment to see what the screens show you (save and translate as necessary) to your heart's content.

I am NOT BMW-trained in anything, have NEVER been a professional in the automotive industry, and anything contained in the attached pdf is simply based upon my own concepts derived from maintaining my own cars for 50-plus years, and examining & translating the INPA screens (most of which are in original German in my version.

So any comments, observations, corrections, suggested additions, or differing concepts are welcomed. I am trying to offer my self-taught concepts and welcome any feedback to improve/correct those concepts, and hopefully encourage others to do the same.

George

[Atx328]

I appreciate the suggested path to get familiar with inpa.

I ended up being about 10 oz low on Freon so it was an easy fix this time.

[gbalthrop]

Originally Posted by Atx328

I appreciate the suggested path to get familiar with inpa. I ended up being about 10 oz low on Freon so it was an easy fix this time.

That is certainly the most likely explanation for sometimes needing to warm up the engine compartment before the Refrigerant Pressure Sensor allowed the Compressor Valve to begin pumping.

Just curious how that was determined: with what equipment & procedure?

Did shop simply add R-134a by gauge readings, did you evacuate, measure the weight of R-134a removed, and then recharge to ~ 20 Oz. or ???

Have you gotten a chance to Read Fault Codes in ALL Modules with INPA?

Thanks,
George

[Atx328]

Originally Posted by gbalthrop

That is certainly the most likely explanation for sometimes needing to warm up the engine compartment before the Refrigerant Pressure Sensor allowed the Compressor Valve to begin pumping.

Just curious how that was determined: with what equipment & procedure?

Did shop simply add R-134a by gauge readings, did you evacuate, measure the weight of R-134a removed, and then recharge to ~ 20 Oz. or ???

Have you gotten a chance to Read Fault Codes in ALL Modules with INPA?

Thanks,
George

happened to have a few hours free last weekend when I drove past a shop that had done AC work for my daughter's Acura, so I popped in and they performed a diagnostic on the cheap. They even gave me the option to add the refrigerant myself but I was feeling particularly lazy, so I just had them perform the work.