95 525i AC not getting power

[Sleepyhead97]

Hello,
My AC compressor is not getting power. I have checked all the fuses. Looks like Previous owner(s) hot wired the AC to work on FULL TIME. This is a problem.
Also looks like they hot wired the aux fan to run full time. Shown in the video, this is what the three prong lug is, I am suspecting. The Fan beings to run the moment I turn the key on.



The AC button (SNOWFLAKE) will not turn on even when I push it. The recirculate will not turn on either. The system has the correct pressure of r134.
Would the AUX fan being hardwired cause the issue of the AC compressor not engaging?
Do you know what I should be looking for? I think maybe the head control unit is bad?

Please see video. I am not a cinematographer.

Thanks.



https://www.youtube.com/watch?v=FAA7tL4vBrs

[GregT53]

What color is the wire that was used to make the compressor run constantly?

Looking at a wiring diagram, it shows a black/yellow/red wire running from the compressor control relay to the compressor. If this wire was pulled from the relay and hard-wired then it might be as simple as reconnecting to the relay. I am not an electrical expert, far from it, but I can tell you what the diagram shows. Someone on the forum will likely know how to piece this back together.

[Sleepyhead97]

tmp_8303-20170423_2016091593709317.jpg

They spliced into purple wire . Then ground black to brown on the three prong pigtail, which I assume is the auxiliary fan plug.

[GregT53]

This wiring diagram may be of some help. Like I said, I am no expert in this area, but maybe having the diagrams will help you sort out what is supposed to go where.

Here is a link to the diagrams for 1995 vehicles. In the first few pages you'll see a legend for wire colors and symbols for the various elements in the circuits. http://www.armchair.mb.ca/~dave/BMW/e34/e34_95.pdf

[Sleepyhead97]

Thanks Greg. This diagram is a bit better than what is in my manual.

Can someone confirm this plug is for the aux fan?
Anyone have pictures of this plug correctly connected?

[zkd]

Thanks Greg. This diagram is a bit better than what is in my manual.

Can someone confirm this plug is for the aux fan?
Anyone have pictures of this plug correctly connected?

Ok I know for a fact that the fan plug which is disconnected goes into a Radiator Aux Fan Switch on the side of the main radiator. this controls the speed of the fan, it has 2 speeds. the higher one is when the cooling system need more air.

61311378073-lg-wp.jpg

from your video I can see that is missing and a plug is in it's place.



once you get all your wiring and relays sorted, if the AC doesn't turn on then the problem would be in the control unit. it is located behind the microfilter behind the HVAC unit. can reach it but peing the side panels (carpeted) around the main HVAC, from the passenger side and drivers side. it has 3 plugs 2 on passenger side and on on the driver side. then slide it out and replace it with the same part number from a breakers yard.

018.jpg

MF-7.jpg

it can look like this:

control_unit_1.jpg

or like this:

BMW_E34_Heizung_Klima_Steuergeraet_Klimasteuergeraet.jpg

depending on which model you have.

I hope this helps

[Sleepyhead97]

THANK YOU!! Great info

[GregT53]

As connected in my car: You are looking from passenger fender side. Plug end with two prominent red/black wires goes to what I presume is the compressor; the other end (second image) goes back toward the firewall. It's hard to tell the wire colors on the second photo, but the top wire appears to have a light colored stripe.

As for the IHKR (aka control unit) mentioned in the previous post, if you do get into that I highly recommend you treat your car to a fresh microfilter, quite possibly the most neglected filter in the car. You'll probably find years worth of debris like leaves, pine needles, and bugs that made it their final resting place which you can vacuum out. Your blower motor will thank you for the breath of fresh air and the lessened load.

Sorry about the photo attachments. I don't think they come through on a mobile phone, but they are visible on a computer. Good luck. Hope you get it sorted.

[Sleepyhead97]

With the knowledge of a missing sensor, and my guess that the pressure switch went out, my system is now working!

I installed a new AUX fan switch, and replaced the pressure sensor on the accumulator, and everything started humming. Very happy it worked out!

Thanks!

[zkd]

good for you.. glad it worked out.