2002 525i touring // AC Question

[williamtii]

Hello All,

I am hoping someone can point me in the right direction on my A/C Issue. A/C has worked fine on this car since we got it about 5 years ago. Last year a new Condensor Fan fixed my no AC issue when firing it up in the spring, and I usually add a can of R-134 every two years.

This year I get no A/C and I can see the Compressor is not kicking on so figure it needs some more refrigerant. Upon hooking up the gauges with A/C on MAX I find both High Side and Low Side at 85 PSI.

Never seen this before, what should I be going after? FYI Coolant level is OK, I've seen that can make a difference.

Thanks,

William

[JimLev]

You should be fixing the leak first so you don't need to keep adding R134a to the system.
The leak will probably keep getting worse.

[edjack]

And charge the system by weight, not pressure.

[BimmrMeUpSnotty]

Yep, E39's after 12/97 it was like, what? 750 grams +/- 10 grams, or 1.65lb

If you were adding 134 at all, you have a leak. Either replace all the o-rings on the coonections to the compressor fittings, the o-rings on the connections to the condenser, the o-rings to the pressure switch, and the o-rings to the evapiorator box at the firewall.
Or, have the ac system serviced, they will suck out all the old stuff, put a vacuum on the system, to see if there even is a leak. Chances are, you kept adding refrigerant, and if you added too much, the system will never energize the gas properly in the compressor. If the system fails the vacuum test, then they will have to figure out where the leak is, add a dye into the system and see where it is leaking out, then replace that o-ring, or the part that has a hole, like maybe a rock hit the condenser or something. At this age, all the o-rings should all be replaced anyways, then go from there.

[williamtii]

I have not added any additional refrigerant, apologies if I was unclear. The same refrigerant is in there now as there was last year when the system worked. When I saw the compressor was not engaging, low refrigerant was my first guess. I always check the pressures before doing anything and see that both sides are an even 85 PSI.

I do not suspect a leak either, if both sides are holding fine at 85psi. Why would both sides be balanced?

[BimmrMeUpSnotty]

Then check the wire to the compressor for 12 volts, and then check if the compressor clutch is working.

[goz777]

is the ambiant air temp gauge in the dash working? had a simillar issue with an 2001 530i ended up being the sensor for the external/ambiant air temp, i too suspected low gas but gas was fine, i then thought faulty compressor clutch(ended up just jumping 12v straight the the compressor & running engine with it like this to test, clutch engaged & aircon was cold)id had a faulty ambiant sensor for about 3/4years & it never affected it then for some unknowen reason it did....replaced the sensor & a/c worked as it should without any issues.

[jclausen]

First charge th system correctly and recheck equal numbers can mean failing compressor

[williamtii]

Thanks to Bimmrmeupsnotty for the easy check for voltage tip, thats an easy one........

With the A/C on MAX Blow I get 5V at the compressor so something is amiss upstream.

I was able to get an alligator clip on the single-pin connector on the compressor so I hooked it up to a deep cycle battery I have. Ta-Da! compressor spins up nice and cold air blows. Low Side reads 32PSI and High Side 160PSI.

What would be stopping the compressor from getting voltage?

[BimmrMeUpSnotty]

Thanks to Bimmrmeupsnotty for the easy check for voltage tip, thats an easy one........

With the A/C on MAX Blow I get 5V at the compressor so something is amiss upstream.

I was able to get an alligator clip on the single-pin connector on the compressor so I hooked it up to a deep cycle battery I have. Ta-Da! compressor spins up nice and cold air blows. Low Side reads 32PSI and High Side 160PSI.

What would be stopping the compressor from getting voltage?

Ahh, great! You've narrowed it down. Inspect the wire for a fray, maybe the plastic sleeve got scrubbed off exposing copper, went unchecked and now has oxidized into the black copper death, and now there is resistance built up and voltage is not flowing through enough anymore.

[williamtii]

Well the wire inspection did not lead anywhere. I checked for voltage as high up as I could before it dissapears into the harness and found the same 5 Volts.

That to me is strange. The A/C positive wire is getting 5V when the car is off, on with the A/C off, and with the A/C on Max.

[BimmrMeUpSnotty]

The IHKa panel sends the signal to the compressor clutch to engage, depending on what the pressure switch sees. If the system is over or undercharged, this determines wether the 12 volts gets to the clutch to engage or not. So make sure your system is properly charged, and that the pressure switch is getting proper readings. Check the aux fan relay in the electoric compartment underneath the passenger side cabin filter. It could be a lazy relay. Heck, check that the 75amp fuse behind the glove box is good, to make sure the aux fan is working properly, but I don't think that puts a hold on the IHKA, might be wrong on this, disconnect the aux fan harness in front of the condenser, plug it back in, it may have just come unplugged. Ambient sensor, is it reading properly on current outside temperature? If it's the IHKa control module, a replacement may need to be coded, not too sure on that though.

[mattmar1]

no coding needed when replacing IKHA panel

[djb2]

I haven't checked that specific circuit, but 5V present on a disconnected automotive circuit usually indicates that the module is monitoring the load for disconnection or short circuits.

This works by the module supplying 5V through a high value resistor. If the module observes a bit over 0V, that suggests that the proper load is connected. If it sees above 5V (usually a 6V to 8V threshold, it reports a short to +12V). A short to ground is detected by either observing close to 0V with the test current, or briefly applying full operating current with higher current loads (which is why you get flashing lights when you substitute LED lamps).

There is a pretty good chance that a diagnostic program such as INPA will point you directly to the problem, perhaps without opening the hood.

[williamtii]

IHKA brought back a distant memory. Looks like I did this two years ago, nice going brain.

https://www.bimmerforums.com/forum/s...or-Not-Working


Well this might do it! Went to unplug the Aux Fan to check for voltage and found this;



Once the connections were cleaned the fan is getting 12V. I tried stripping the fan wires and applying 12V direct and it does not spin, so lets see what FCP has to say about a return.

I got 2 IHKA units at the time but one ended up DOA so I just have the one in the car. Might be worth picking up a spare if Im going to be doing this every 2 years! Reverting with an update once the new fan arrives.

[williamtii]

OK so the new Aux Fan came in. I figured I would plug it in first before removing the bumper and replacing it. Bummer, it did not spin.

Checked fuses 7,20,22,75 again and all are fine. I tested for power at the connector again with the A/C on MAX and saw 13V+ using the Brown (ground) Wire and the Black (power) Wire.
I also tested with the A/C off and got 13V+. Why is the fan getting full power at all times? From my reading it should only turn on when the A/C is on or overheating, and testing was done cold.

So I put 12V directly to the new fan (Thick Blue + Black Wire) and it does not spin. Am I missing something here or is the new fan bad?

[BimmrMeUpSnotty]

The fan starts to run when it gets a PWM pulse signal.Thats what triggers it, and commands it to run at different speeds accordingly.

[mattmar1]

to bump up a bit what snotty stated, the DME monitors the temp and supplies the PWM signal to control the aux fan speed. that signal is on the 3rd wire on the connector.

[BimmrMeUpSnotty]

Yup, it’s basically a brushless motor and you have a speed control that starts the motor when the DME gives it the go ahead, and controls how fast it wants it to run, and when to shut down.

[williamtii]

Ok thanks, that is what I have read as well. I am currently not getting any voltage to the PWM at the connector.

Is there a practical way to bench test the new fan before installing? I seem to remember from when I first replaced it two years ago that 12v to the Black and Blue wires would run it, not having to involve the PWM.

If my problem is not the fan I will keep looking upstream to the IHKA, FSU, etc. I would like to make sure the fan works though, before going ahead and taking the bumper off. The missus has dragged it off a curb or two so there's a bit of epoxy holding things together.........

[williamtii]

This one is solved, turned out to be the connector only. I did not want to replace the old fan without proving it was dead first, so I did what any logical person would do. Bought everything it could possibly be and headed up to a friends that knows more about electronics than I can stay awake for. Looks like he robbed a high school shop class from 1978. The PWM had not been showing the required 4-6 Volts, but both fans spun when hooked up to a signal generator. From there connected everything back up with alligator clips, bypassing the connector, and everything fired up as normal. I was trying to get a good shot of the signal on the oscilloscope but only captured a blip

[effduration]

Thanks for follow-up...So it was connector at the Aux fan? I couldn't see a picture in post #15 above.

Thanks

[williamtii]

Yeah the connector was all corroded. When I cut and stripped the car side back I got 12V to the fan, but nothing from the PWM to make it spin. I tried jumping the temp sensor to make it spin and got nothing there either. All fuses checked out, and I even got another eBay IHKA which did nothing.

From my Aux fan adventure two years ago I was reading about 4V from the PWM when the key is in position 2 which meant the fan was getting signal. This time around I had no voltage so needed a signal generator + scope to see if the fan would spin.

Both new and old fan spun up fine, the cool part was controlling the speed with the signal generator knob. When I hooked everything up bypassing the connector A/C came on and fan spins as it should, so I hard wired the old fan back in place and called it a day.

In the end I think my problem troubleshooting was looking for voltage from the PWM wire WITHOUT it being connected to the fan. Even if the fan is not working, the DME needs to see that its there. Lesson learned, fix the broken thing even if you haven't proved it to be the source of the overall issue. Thanks to all above for the help.

[RicardoV]

I recently went through the whole A/C doesn't work, Aux Fan doesn't work, can't find what is wrong and I don't have a signal generator to test PWM wire. After buying a new fan, IHKA, etc, I developed this test procedure that doesn't require a signal generator and would have saved me a bunch of money and many troubleshooting hours.

You are right that the DME needs to see the fan for it to 1) send it a signal before it will activate the A/C clutch. In fact, if it doesn't see the fan, it will create a "lock" on the A/C clutch so that you can't test it using IHKA with INPA or ISTA. Since it is only the DME that controls the Aux Fan operation, through the PWM wire, all other tests, i.e., shorting or disconnecting Coolant Temp Sensor, disconnecting A/C pressure switch may not provide you with an accurate troubleshooting result for the Aux Fan.

TLDR: Summary: Before spending money on parts, if Aux Fan is not working, and/or if you are getting an error: "00007D, DME: Activation, electric fan"; then check for 12V power, ground, and DME continuity at connector X82 (fan connector). If you don't have 12V power or continuity on black wire, check 50 amp Max fuse #75 behind the glove box (or your BMW model equivalent). If you don't have ground continuity If no continuity on PWM wire (yellow with red stripe) coming from DME connector 6004 Pin 4 and connector X82, check for short in PWM wire. If you have power, ground, and PWM continuity then replace the Aux Fan.


Procedure to test for proper operating conditions for Aux Fan without a Signal Generator.

Tools required:
Digital Multimeter (DMM), or 12V Test light and Continuity tester

Procedure:

1) Disconnect Aux Fan, M9, from 3- wire connector X82 (vehicle side of the connection)

2) Determine if you have 12V power at the black wire of the X82 connector by using DMM or Test Light to check for Battery power. If you don't have power, test for continuity with DMM or continuity tester, from the black wire to 12V Positive terminal on the driver's side of the engine. If you have continuity between X82 connector and Positive jump terminal then replace the 50 amp Max fuse #75 behind the glove box and test for 12V power again. If you don't have continuity, inspect, repair, or replace the 12 gauge black wire or pin on X82 connector.

3) Determine if you have ground at the brown wire of the X82 connector by using DMM, Test Light, or Continuity tester by either testing for 12V power or by testing continuity to body or connector X11, the body ground connector located on the passenger side fender with multiple brown wires. If you don't have ground then inspect, repair, or replace the 12 gauge brown wire or pin on X82 connector.

4) Determine if you have continuity on the PWM wire, yellow with red stripe, of the X82 connector by using DMM or Continuity tester. The PWM Aux Fan wire can be found on DME connector 6004 Pin 4. Test for continuity from connector 6004 Pin 4 to PWM wire, yellow with red stripe, on X82 connector. If you do not have continuity then inspect, repair, or replace the 18 gauge yellow with red stripe wire or pin on X82 connector.

5) Reconnect Aux Fan, M9, to X82 connector and start vehicle with A/C on. If Aux Fan begins to operate, check for A/C clutch engagement. If Aux Fan does not operate and no other trouble codes are present, then replace the Aux Fan.