2002 E39 - AC Compressor Not Working

[williamtii]

Hi All,

It's warm season here in CT and naturally the wagon is blowing warm air. It is the dual climate Auto HVAC System. The compressor is not kicking on the the Static Pressure is reading Low 125psi / High 130psi

I found these happy helpful links and it seems like either the pressure switch or HVAC Control could be the issue but not sure with the pressure readings I am seeing. Is Static pressure that high normal? I realize the low would drop if the compressor was kicking in but that seems quite high. It worked last year and have I not added any refrigerant.

https://www.bimmerforums.com/forum/s...mpressor/page2

http://www.bimmerfest.com/forums/sho...d.php?t=695551

[jmc1590]

Static pressure #'s like that don't seem out of the ordinary, depending on ambient temperature. (Google an R-134a temperature chart.)

I guess the troubleshooting I would do is put a meter on the AC compressor clutch line. With AC on, should be 12v (or close.) If not, could be pressure switch or DME. Do you have access to INPA? It can activate the compressor independently of the pressure switch. It can test / validate the switch too for that matter.

Check fuses. I believe the IHKA unit supplies the power for the AC clutch.

A wiring diagram from newtis would help as well!

Good luck.

James

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[williamtii]

Thanks James,

No access to INPA unfortunately, I have seen some threads with good info though. I will see if the Compressor is getting power as the first test.

I am sort of hoping that it is the IHKA / HVAC Unit. Lost a few buttons off it and the Blower started making noise over the winter so I could do it all in one go.

[williamtii]

Update. I sent 12V directly to the compressor via the one wire connector. Nice and easy to do, thanks BMW. Clutch engaged immediately and runs nice and quiet, High/Low Pressures are good.

I also checked the compressor connector for power with the A/C set to MAX and it read 36V ! Why is the car sending so much juice to the compressor?

[jmc1590]

Update. I sent 12V directly to the compressor via the one wire connector. Nice and easy to do, thanks BMW. Clutch engaged immediately and runs nice and quiet, High/Low Pressures are good.

I also checked the compressor connector for power with the A/C set to MAX and it read 36V ! Why is the car sending so much juice to the compressor?

I'm more concerned with where the 36V came from! 12V system, 14V occasionally when running.

Glad to hear the compressor clutch engaged. Now it's chase down the wiring leading to the clutch. Do you have an extra IHKA unit you can swap?

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[williamtii]

I picked up two IHKA's off ebay they are on their way along with new cup-holders. Will be nice to clean up the console even if the IHKA isn't the issue.

Further tests have led to further confusion. I noticed that the AUX fan does not come on when the A/C button is pressed so I did some digging there. Jumping the DTS at the lower Rad Hose did not get the Aux Fan to spin. From the Pelican Article below 5V should be going to the sensor. I get 0.35V

https://www.pelicanparts.com/BMW/tec...or_Removal.htm

The Aux Fan connector is getting 14V at the Blue Wire and 2V at the PWM Wire with the AC on, but does not spin. Supplying 12V direct did not get it to turn either so I *was* thinking the fan or fan resistors that were bad:

http://www.bimmerfest.com/forums/sho...d.php?t=543182
http://www.bimmerfest.com/forums/sho...d.php?t=572388

That is until the condenser started spinning on its own. With the DTS and Aux fan disconnected! I plugged both back in and the Compressor kept running happily, then the Aux fan came on! It is definitely sad and wobbly but spins right up. I'll pick up another but what the heck is going on? I thought that the Aux Fan and DTS had to be plugged in and working for the Compressor to come on?

[edjack]

36 V sounds like cockpit error. There is no 36 V source on the car.

There are no fan resistors. The DME controls the fan speed via the PWM lead, based on rad outlet temp.

the condenser started spinning on its own ​WHAT??!!

[jmc1590]

Aliens. Definitely aliens...

While trying to get the fan running, I'm assuming you had enabled the AC. Then started playing with the sensors. I suspect something finally sent a "OK to enable" signal to the IKHA. Or your control unit is doing its own thing. I've had a dual pressure sensor go whack and cause compressor issues.

As far as the fan goes, it's PWM controlled. It should get 12V all the time, with the small wire defining duty cycle. Other than in INPA / DIS, I haven't found a way to replicate the duty signal.

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[williamtii]

Sorry meant the COMPRESSOR came on all by itself, not the condenser. Yes A/C button was activated while messing with the DTS and Aux Fan.

I though the meter was bad when I saw 36V but if I put it on the battery and Alt it reads steady 13.8-14V. Back on the Compressor it would start at 35.5V and creep up and hold at 36V.

For the past three days A/C has been working, and the Aux fan wobbles about 30% of the time. If it wont start again I will surely try to get a video.

I liked the Dual Pressure switch idea, but the compressor fired up before i got that far. Will update the thread again if there are any changes and once the IHKA comes in to swap.

[williamtii]

Also to Edjack above, did they do away with the resistors on the later cars? Have seen other threads where everything is built in on the Aux Fan, and RealOEM has the part greyed out for my VIN:

http://www.realoem.com/bmw/enUS/show...diagId=64_0832

I see on other sites that the Resistors apply through the end of production so hard to tell!

[williamtii]

To Close this out, a new Aux Fan solved the issue. Put the ebay IHKA too so I have full button power!

[vmummer]

I have a 2001 E39 530 and my A/C compressor is cycling. Reading with a simple gauge before A/C Button is pressed shows 145 PSI, Once I turn on the A/C, a few seconds later I can see the Clutch engage, gauge shows 46 PSI. The AUX fan starts blowing full blast!. Approx 30 sec, clutch dis engages. Approx 30 sec, I can hear the Clutch Engage.

With INPA, I took some readings, on the Pressure Sensor:
Before Engine Running: 1.7
Engine Running (no A/C): 1.6
Engine Running (A/C on): 3.9
Engine Running (AC Button AC, Clutch disengage): 4.1

Any suggestions?

[vmummer]

Want to provide an update. Did some more reading with others having the same type of issue. One issues is there is too much pressure. So I today I put the gauge back on the low pressure side to check the reading again. Today the gauge showed when the compressor was engage ~55 PSI. So I let out some refrigerant to approx 42 psi.

This keep the compressor engaged and also INPA - Pressure Sensor is 3.5 when Running. Today was a cooler day and seem to keep working. The end of this week it should be getting warmer and hop that was it.

Thanks Everyone!