E34 A/C Always on

[Frank87]

Car: 530iA V8 Sedan (12/1993 Euro) & 525i (M50) Touring (1995 Euro)
A/C Type: Manual A/C

I have searched on this forums and other forums. I came across a post on this forum where someone has the exact same problem. However, the link provided there to a possible solution no longer works.

Problem: After starting the car, the A/C turns on and stays on. No control or led from the A/C button or AUC button.
I thoroughly overhauled the A/C system since I bought the car cheap with a boken A/C compressor.

I have replaced:
- Dryer
- A/C Compressor
- A/C Condensor
- All small O-rings at junctions and metal hose adapters

After that, I put 1200 PSI Nitrogen on the A/C system. After 45 minutes, it still had 1200 PSI. I consider the system to be sealed.
I then vacuumed and filled the system with 1550Kg R134 including PAG oil. The system now cools excellent. But it won't turn itself off.

I then:
- Changed the microfilter and took the black A/C computer with 3 sockets out. Carefully cleaned that computer with compressed air (low BAR).
- Used socketcleaner on the sockets and connectors to abolish any interference from grime
- Plugged the computer back in.

Now, when I plug the computer back in. I am able to use the A/C and AUC buttons. The green LED lights up! However, after starting the car, it takes about 10 seconds before the buttons no longer respond. Although the buttons can be pushed in the beginning. The A/C compressor won't respond.

I then:
- Checked relays. Switched A/C relay with identical horn relay without any result
- Checked for any fault codes, no codes
- Checked the functioning of the needle in the evaporator by laptop, it measures temperature (I guess it does so correctly.. always between 3 and 8 degrees celsius)



So, unless the computer from the wrecker was also busted, I do not know where to continue this operation. Any ideas / suggestions? Again, the system runs great.. but won't shut off.

[632 Regal]

I had one where the AC compressor clutch would stick but doesn't sound like your issue.


Now, when I plug the computer back in. I am able to use the A/C and AUC buttons. The green LED lights up! However, after starting the car, it takes about 10 seconds before the buttons no longer respond. Although the buttons can be pushed in the beginning. The A/C compressor won't respond.

Does the green light still go on and off?

Did you try and remove the fuse and see if it shuts off?

There is also an outside temperature sensor and a heater core temperature sensor that could be faulty adding to the fun.

Welcome to the forum!

[Frank87]

- Green LED no longer functions when the buttons are blocked out
- Did not test with fuse removed but checked all fuses and they check out ok. Will test with removed fuse
- Will test the other 2 sensors but this still does not explain why I cant manually control the AC

[632 Regal]

- Will test the other 2 sensors but this still does not explain why I cant manually control the AC

Yes real strange. The sensors might be getting stuck? Trying to narrow in on the issue.

[Frank87]

Update:

- Installed an A/C computer from another wrecker (the black box with 3 sockets near the cabin filter)
- Replaced the evaporator temperature sensor (On the right side of the pedals right behind 1 cover)

All ok now. The first computer from the wrecker was probably busted.

[632 Regal]

Success! Glad to hear it.

[Frank87]

Update:
The exact same problem appeared again. The compressor will turn on a few seconds after the car has been started.

Pulled the codes from the car. Nothing special on the A/C system. I can only shut down the compressor if I:
- Remove the compressor relay
- Remove fuse 9 and/or 29. Both 9 and 29 shut down the compressor- Unplug the compressor (duh)

I have:
- Replaced the A/C computer (wide black box with 3 sockets) with one I know is working (working wrecker)
- Checked the evaporator sensor with OBD equipment. Works and gives correct temperature readouts

For some reason, I think the A/C computer I thought was busted a while ago, wasn't busted at all. I now have 4 A/C computers here. 1 may be busted but the other 3 work 100%. All tested by the guys who supply and who are trustworthy (no cure no pay).

I have no idea where to look... I get no codes and the components of the A/C system are ok. I have the regular IHKR manual A/C.

[shogun]

I guess you know that the AC is automatically also on when the AUC is on, no need to to push the AC button then?

[Frank87]

I know that and I have AUC. The thing is, once the car knows something is wrong, the * and AUC buttons no longer respond. I can't even control the AUC or recirculate mode.

When I disconnect and reconnect the IHKR computer, it shortly responds with leds when pushing the buttons. No matter what I push however, it does not give me control over the compressor. I CAN use the recirculate button at that time.. but only for about 5 minutes before I can no longer control the 3 buttons. Somehow, the car or a system knows something is wrong.

[whiskychaser]

The IHKR doesn't directly control the compressor - the DME does. Fuses 9 and 29 provide the trigger and main supply voltage to the compressor relay but it will only be thrown if the DME grounds the trigger side. Or something else does - maybe a short to ground?

[Frank87]

The trouble with these electrical problems is that I have no idea where to look for a ground problem. I am currently trying to find out how much earth points the E34 has to ensure those are all ok.

[whiskychaser]

On the M60 DME, pin48 will provide the ground for the compressor relay trigger. I'd just unplug the DME and see if you have continuity at the plug opposite that pin. If you do, the compressor is always going to run. I doubt it is going to be that simple but it is worth ruling it out

[Frank87]

SOLVED & STRANGE

A vacuumleak in an air hose running from a pump (secondary air pump?) directly into the throttle body made the engine run a bit rough and was also the cause of the compressor constantly running.

Yes... this sounds strange.. But listen up:

Start
- When I bought the car, the compressor was busted and I replaced it. That replacement compressor ran constantly and I had no control over the compressor.
- I discovered the vacuum leak, temporarily solved the vacuum leak and got control over the compressor back. I did not think of any connection between these 2 things
X months later
- I lost control of the compressor, compressor ran constantly and the engine was somethimes a bit rough
- Roughness increased and I looked for a vacuum leak
- Found the vacuumleak in the same place, repaired the vacuumleak permanently and got control over the compressor!

YouTube

https://youtu.be/K7ntubwPl2A

[whiskychaser]

I have read this three times and watched the video. And I am still none the wiser. I don't know why this works and cannot explain it. If someone else can, I'd be interested to learn:-)

[genphreak]

Good find. I'm going to take a look on mine and see what I can find out... thanks for sharing!!

[632 Regal]

Thanks for the update Frank,

I will disconnect that hose on my car after the storms pass. It makes no sense to me at all, what would the ac have to do with a vacuum line?

Either way I am curious enough to go do that says a lot. lol

[Frank87]

Guys trust me.. This was the fix when the compressor was constantly running earlier this year.. I thought of a coincidence.. Right now, this is again the fix.. it is no longer a coincidence.

[whiskychaser]

Guys trust me.. This was the fix when the compressor was constantly running earlier this year.. I thought of a coincidence.. Right now, this is again the fix.. it is no longer a coincidence.
You are not nudging some hidden electric loom by any chance? ;-)

[632 Regal]

98° in the shade and the car is not in the shade... I am definitely going to do this though.

[Frank87]

So I got some more issues on this A/C system. As posted before, fixing somekind of vacuum hose also gave me control of my A/C compressor.

I now replaced the resistor at the aux fan. I have a Bosch unit and used an original Bosch resistor. Fan works on both speeds now (test with piece of wire on the right connector).

However, once the key goes into position II, the aux fan continuously blows low speed. Even when the a/c is switched off.

Anyone knows why / how the aux fan would run continuously?

[632 Regal]

So I got some more issues on this A/C system. As posted before, fixing somekind of vacuum hose also gave me control of my A/C compressor.

I now replaced the resistor at the aux fan. I have a Bosch unit and used an original Bosch resistor. Fan works on both speeds now (test with piece of wire on the right connector).

However, once the key goes into position II, the aux fan continuously blows low speed. Even when the a/c is switched off.

Anyone knows why / how the aux fan would run continuously?

So the fan runs when the engine is on and the AC is off? Mine does not run in position 2, just went out to make sure.

If so... Bad switch at the radiator? Disconnect it and see if the fan still runs. Pretty much impossible unless your new resistor is messed up.

[Frank87]

The fan even runs when the engine is off. As soon as the key connects (lights and power options become available), the fan blows low speed. Doesn't stop.

[shogun]

That means in ACC position of the ignition key. I would suspect the ignition switch behind the lock, #3 http://www.realoem.com/bmw/enUS/showparts?id=HE23-USA-04-1993-E34-BMW-530i&diagId=32_0908
Check if there are some wires touching.

I would have checked more in detail, but without a model, engine, built year in the signature or profile, it is difficult. Which ETM built year to check? Here we go, there you have them all http://shark.armchair.mb.ca/~dave/BMW/e34/

Why do you not add a signature like Regal has it?:
95 E34 530I V2.08

Edit after some minutes: I found it in your first post 3 pages before, so please make a signature like this
Car: 530iA V8 Sedan (12/1993 Euro) & 525i (M50) Touring (1995 Euro),A/C Type: Manual A/C

Then you have it there in every post, makes it easier to help you, thanks

[genphreak]

What happens if you disconnect the wiring harness from the rear of the HVAC control unit (the module with the temp controls, AC switches, etc.in the dash? What if you disconnect the AC switch as well/instead?

Does the compressor come in in ACC still? If not, your problem is either in that, or with a modification made to the compressor wiring by a P.O.

Perhaps try a new HVAC control unit

The pressure switch on the drier is a good place to check- there are 2 and 3 wire versions drier replacements around and many AC shops will use whatever they get/have. There are some common wiring mods (near the compressor) made to these BMWs (E28, E30 and E34) which you may find have been botched/gone bad/corroded or come loose...

[Frank87]

genphreak had a good point there.

Over the past few months, I had control of my A/C so I focused at rebuilding the alternator and steering pump. Yesterday, I lost control of the a/c again. The work I did on my car yesterday involved checking the belts and pulleys. I removed the fan shroud, fan, AUC connector and the filterbox + MAF.

After putting everything back together, as said, I lost control of the A/C system and the compressor was on. With the AUC in the back of my head (that one is a suspect too!), I first removed the filterbox to see what I could find. Under the filter box, I saw the location of the dryer and the pressure sensor. Although the dryer and sensor look ok, the wires look bad. The pressure sensor has 2 branches of wiring that end in 2 connectors. It still looks original.

With removal/fitting the filterbox, I may have touched or moved something that causes somekind of short-wiring or jump-wiring with those bad connectors. I have ordered a new dryer and a new pressure sensor. That sensor comes complete with those 2 branches of wiring. I will be replacing the dryer and sensor this saturday and will fix all wiring that looks bad.

In addition, I have found a single wire running from that sensor branch all the way into the DME/AGS electronic box (passenger side). This may be the pressure signal the DME needs to cut off the compressor if the pressure gets too high. I will follow that cable all the way into the box and check if it is properly isolated all the way. I may replace it with a stronger wire to increase the quality as it is thin and runs through all kinds of equipment. I would be relocating the wire to make it more reliable.

Updates and pictures will follow.

[Frank87]

Here some pics of the strange wire. Can anyone tell me if your V8 with A/C has that wire as well? Starts at the dryer..


http://img.photobucket.com/albums/v432/PMAngelEyes/Wire20start_zpsveimyoru.jpg

http://img.photobucket.com/albums/v432/PMAngelEyes/Wire20through_zpsc8ljj5zl.jpg

http://img.photobucket.com/albums/v432/PMAngelEyes/Wire20box_zpsefp3lbis.jpg

[632 Regal]

After putting everything back together, as said, I lost control of the A/C system and the compressor was on. With the AUC in the back of my head (that one is a suspect too!), I first removed the filterbox to see what I could find. Under the filter box, I saw the location of the dryer and the pressure sensor. Although the dryer and sensor look ok, the wires look bad. The pressure sensor has 2 branches of wiring that end in 2 connectors. It still looks original.

With removal/fitting the filterbox, I may have touched or moved something that causes somekind of short-wiring or jump-wiring with those bad connectors. I have ordered a new dryer and a new pressure sensor. That sensor comes complete with those 2 branches of wiring. I will be replacing the dryer and sensor this saturday and will fix all wiring that looks bad.

In addition, I have found a single wire running from that sensor branch all the way into the DME/AGS electronic box (passenger side). This may be the pressure signal the DME needs to cut off the compressor if the pressure gets too high. I will follow that cable all the way into the box and check if it is properly isolated all the way. I may replace it with a stronger wire to increase the quality as it is thin and runs through all kinds of equipment. I would be relocating the wire to make it more reliable.

Updates and pictures will follow.

Without pulling the airbox I can see the top of something with a couple wires going into it could be the drier/switch. I have no single wire except the one to the compressor, not sure where that goes but not like the one you have. No other single wires anywhere else in that general area unless I seriously have to pull the airbox to see it. Nothing single running by the AC hoses either. In your top picture I can't see exactly whats going on by the connector (too dark) but no, no single wire like that anywhere on mine.

[Frank87]

Ok, this is good. With Regals answer I knew this wire was not original. Stripping the isolation (was not BMW isolation, regular isolation tape) gave me this:


http://img.photobucket.com/albums/v432/PMAngelEyes/Man20made20wire_zpslozk3k0r.jpg


So there we have a T junction with some soldering. The filler is clearly visible. This is 100% man made.

Since all 4 wires of the pressure regulator properly run into the loom, I cut the wire halfway and re-isolated everything with duct tape (for now).

And yes, guess what, I got control of my A/C system again. No other variables were touched so apperently, this wire was the problem.

To be careful, I will keep the compressor disconnected until friday. I will then replace the drier, pressure switch, radiator temp switch and will properly fix and re-isolate all wires.

In addition, I will follow that man-made wire into the interior and see where it ends. After doing all that, I will run the car with the a/c on and use diagnostic stuff to monitor the pressures. If the car reads the low and high pressure, I consider it to be safe and will start driving with the AC again.

More pics will follow.

[632 Regal]

That wire is some sort of half assed fix. I'm wondering what is wrong with the original wire if anything.

You are going to vacuum the AC after installing the new drier?

As for monitoring the only thing you should have to do is add refridgerant untill the bubbles just stop passing the sight glass. The compressor should not run until you start getting enough pressure to turn on.

[632 Regal]

So I got some more issues on this A/C system. As posted before, fixing somekind of vacuum hose also gave me control of my A/C compressor.

I now replaced the resistor at the aux fan. I have a Bosch unit and used an original Bosch resistor. Fan works on both speeds now (test with piece of wire on the right connector).

However, once the key goes into position II, the aux fan continuously blows low speed. Even when the a/c is switched off.

Anyone knows why / how the aux fan would run continuously?

Did you get this fixed also? Perhaps that mystery wire is the culprit or another mystery wire to the fan?

[Frank87]

Yes. When I have control over the A/C. The aux. fan won't run unless it has to. When I lost control of the A/C, the aux fan would always run on low speed. That little wire did cause some stuff.

I have professional A/C equipment this friday. It will empty and vacuum the system after which it can add exactly 1,55 kg of R134 + PAG. Ill use the diagnostic equipment to measure the low and high zone pressures. If I can measure the pressure using the OBD/ADS interface, the car knows the pressures as well.

[632 Regal]

Yes. When I have control over the A/C. The aux. fan won't run unless it has to. When I lost control of the A/C, the aux fan would always run on low speed. That little wire did cause some stuff.

I have professional A/C equipment this friday. It will empty and vacuum the system after which it can add exactly 1,55 kg of R134 + PAG. Ill use the diagnostic equipment to measure the low and high zone pressures. If I can measure the pressure using the OBD/ADS interface, the car knows the pressures as well.

Okay good. Just had to mention that because I HAVE seen people replace AC parts without vacuuming the system with less than positive results. You should also drain the oil from the drain points prior to vacuuming IE: the pump or adding the recommended amount can be too much. I have a HVAC and EPA licence from the days of pacman on this stuff somewhere lol.

Have you checked the voltage of the stock wire, 'man made' wire while disconnected to see what might be going on? The 'man made' wire might be back feeding something in an attempt to fix something irrelevant.

What year is yours?

[genphreak]

Yes. When I have control over the A/C. The aux. fan won't run unless it has to. When I lost control of the A/C, the aux fan would always run on low speed. That little wire did cause some stuff.

I have professional A/C equipment this friday. It will empty and vacuum the system after which it can add exactly 1,55 kg of R134 + PAG. Ill use the diagnostic equipment to measure the low and high zone pressures. If I can measure the pressure using the OBD/ADS interface, the car knows the pressures as well.

Nice, how'd it go doing the pressure checks? What the board needs of course is some pics and a little how-to ;-)