A/C on E34

[barneyE34]

Hello everybody, I am new on this forum so I apologies for any future mistakes.

I don’t have AC on my car so I want to install the system. I have all I need from a mechanical point of view but I have some trouble with the electrical part.

Can somebody please explain how the system works ? for example what does the pressure switches do exactly ?

After reading some ETM manuals I formed an idea but i’m not certain.

I wasn’t able to find the codes for the auxiliary fan relays K21, K22, and the compressor relay.

Can somebody help me ?

Also, how many amps does the auxiliary fan needs on full speed ?

[ahlem]

Did there used to be AC on your car and someone deleted it? If so, How much is still there? Do you have access to a similar car in a junk yard to look at?

[shiftfan]

The previous owner tried to install an ac system but in the end, he used an on/off button to power the compressor and that was it.

I don't think the car came with AC, but it did with IHKA , can't imagine how but unfortunately this is the case.

I don't have access to a car from junkyard .

[shogun]

aux fan full speed = high has a 30A fuse, I measured on a good aux fan 18A in Hi, and on a bad one with broken bearing 30A.
This explains the function of K21 and K22 BMW E34 Aux Fan Resistor

[shiftfan]

aux fan full speed = high has a 30A fuse, I measured on a good aux fan 18A in Hi, and on a bad one with broken bearing 30A.
This explains the function of K21 and K22 BMW E34 Aux Fan Resistor

Thank you for your answer and the link.

[whiskychaser]

The compressor relay (K19?) normally lives in the fuse box and he is probably using a switch to trigger that. Have you got the aux relay box (which houses K21 and K22) on the front left inner wing and the radiator switch which drives them?

[shiftfan]

The compressor relay (K19?) normally lives in the fuse box and he is probably using a switch to trigger that. Have you got the aux relay box (which houses K21 and K22) on the front left inner wing and the radiator switch which drives them?

Nop, no auxiliary relay box, i do have a radiator switch but it is in a very bad shape.

Do you have ac on your car ?

[whiskychaser]

Do you have ac on your car ?

Had manual AC on the E34 until it went to the breakers a few weeks ago and I still have the AC control module if you need one :-) The aux fan should come on all the time the AC is switched on. The high/low fan relays live in the aux relay box as per this article: page_2
So I imagine you will need that plus the loom that goes with it from another car. Wiring diagrams are here if you have not seen then already:
Free Phone System Manuals Voice Communications 800 593-6000

[shiftfan]

Had manual AC on the E34 until it went to the breakers a few weeks ago and I still have the AC control module if you need one :-) The aux fan should come on all the time the AC is switched on. The high/low fan relays live in the aux relay box as per this article: page_2
So I imagine you will need that plus the loom that goes with it from another car. Wiring diagrams are here if you have not seen then already:
Free Phone System Manuals Voice Communications 800 593-6000

Thanks for the link but it doesn't show any part number for the relays.
Yes i want to get all thee wires for the ac system from another car preferable with IHKA.
I have the manuals, i searched them pretty thoroughly and have an idea. It goes something like this :

K21 NORMAL SPEED RELAY
PIN 85 → TEMPERATURE SWITCH
PIN 86 → F29 7.5 A
PIN 30 → F25 30A
PIN 87 → PIN 2 AUX FAN

K22 HIGH SPEED RELAY

PIN 86 → F29 7.5 A
PIN 85 → TEMPERATURE SWITCH
PIN 30 → F25 30 A
PIN 87 → PIN 3 AUX FAN

ECU (MS40) - i have a M50b20Tu from an e36 94.

PIN 10 AA AUX FAN IHKA → AC CONTROL UNIT AC SYSTEM
PIN 24 E AC COMP ON → AC RELAY (K19)
PIN 9 A SIGNAL AIR ON → PRESSURE SWITCH


PRESSURE SWITCH ON R12 HAS 2 CONNECTORS

WHITE X126

PIN 1 → GROUND
PIN 2 → K22
→ TEMPERATURE SWITCH

BLACK X127

PIN 1 → ECU
→ K21

PIN 2 → IHKA ????/ NOT SURE



K19 , AC RELAY (NOT SURE AT ALL )

PIN 85 → IHKA
PIN 86 → F29 7.5 A
PIN 30 → F9 15A
PIN 87 → Y2 COMPRESSOR CLUTCH


(I really need those part numbers ), for k19,k22,k21 ) i could try something like 4/5 pin relay for k19 because it needs to start the auxiliary fan every time you turn on the ac max 30 amps, and k21, k22 4 pin relay max 30 amps
what do you think ?

[whiskychaser]

That looks about right. I'd suggest that there may be one loom that connects the aux relay box, fuse box, fan motor, temp and pressure switches together. If you dont have access to a donor car, I'd suggest getting in touch with somebody who is breaking one. You may well be able to pick up the loom, switches and relay box for very little money.