AC failure diag help

[Bdc101]

Honestly, that's one of the things that drives me the most batty with this car. Not only is an OBDII adaptor completely inadequate, but there are four different tools you have to buy (and for PA soft, troubleshoot) just to be able to maintain the damn car. People wonder why there are so many of these in junkyards.



Anyways, if it means getting my AC working before I tow the trailer to the lake with my family on board in July, then the funds will be released...

[upallnight]

Originally Posted by Overboost

The aux fan error or compressor error will show up in the dme error codes. Not sure if PA Soft will pick it up, when I had the issue I ran INPA to see the error. If you have the budget, the Foxwell is a great tool. I have 4 tools I use all the time and they each have functionality that the others do not.

• INPA
• PA Soft 1.4
• Foxwell NT-510
• ELM 327 Bluetooth module to OBD Fusion on my Android phone

If the fan is bad the DME will log a fault and P.A. Software aka BMW Scanner 1.4 will list the fault.

[Bdc101]

Turns out there are three terminals in the pressure switch.

One pair has 6.8k impedance
One pair has 12k impedance
One pair has no continuity.


Bentley has nothing, and I've got nothing.

[andrewwynn]

Turns out that pressure sensor is not the typical sensor switch it's actually a pressure level sensor. It's supplied with 5v and outputs a varied votage depending on the pressure going info the compressor. The computer uses the current pressure on the suction side to determine how fast to run the aux fan (at speeds below 80 kph).

Anyhow enough people have reported the aux fan is non negotiable for AC. Trace why that isn't working.

Unfortunately it's a pwm controlled motor to test manually you need to apply a square wave to the control wire after making sure the main 50A power leads are live. (YouTube shows examples).

Again by far easiest way to test the aux fan is plug in the foxwell drill down Into control > body > HVAC and active test enable the fan. (I think it has a couple speed options).

[andrewwynn]

Originally Posted by upallnight

Might be easier, but you are assuming that he has the equipment and knowledge on how to perform this test.



I, on the other hand, assume that they don't know anything or why else will they be posting on this forum.

Not very accurate assumption. Most people I've advised do know basics of how to operate a DMM so I don't need to hand hold too badly. People will usually say they are a complete novice or indicate in some way how skilled they are.

If I get crickets when I mention "measure the voltage at the main power feed to the aux fan" I will send the person to do some Google learning because they do need some basic even moderate level of understanding of the terminology or I can't help them.

They can do some learning and come back and they will understand or they will have to realize over their head and they can show my post to their mechanic.

[andrewwynn]

Originally Posted by Bdc101

Honestly, that's one of the things that drives me the most batty with this car. Not only is an OBDII adaptor completely inadequate, but there are four different tools you have to buy (and for PA soft, troubleshoot) just to be able to maintain the damn car. People wonder why there are so many of these in junkyards.



Anyways, if it means getting my AC working before I tow the trailer to the lake with my family on board in July, then the funds will be released...

I refuse to use 30 year old software on a 20 year ols computer.

I only use my foxwell for accessing and clearing codes and for example re-sync Key to EWS today when wife's X5 cranked without starting after the battery was stone cold dead from sitting for 8 weeks so a fuel pump. I also bumped up her idle speed 40 RPM because the idle wasn't very smooth in drive at a red light.

I can't code things like make my turn signal not blink fast because I have LED rear turn signals but I refuse to deal with the headaches of the horrible "solutions" of the craptop diagnostics.

Get yourself a foxwell and problems practically jump right out at you.

[Bdc101]

Got my foxwell in, and I get no faults in the AC system.



It does say fault 7D: DME: Activation, electric fan. Does that confirm that the aux fan is faulty?



Also, I was able to activate the AC compressor manually with the foxwell, and it blew cold. But I didn't run it very long. Sounds to me like the aux fan.

[80stech]

I think you have gone as far as your abilities can take you and with that it is entirely reasonable to assume that your aux fan is faulty.

[andrewwynn]

foxwell will activate fan. If the command doesn't work there is a defect in the fan system. Is their always on power at the fan? If you have power at the fan and foxwell won't spin the fan it's faulty

[upallnight]

You got the code that the fan is bad. Just spend the money and replace it. You already spent the money on the Foxwell.