BMW E36 Air Conditioning Relays

All relays are not equal. Especially in a BMW. The pin layout is standardized, but the electrical function of the pins can be different from application to application.

In my case the previous owner apparently didn’t get this and just got three cheap relays from Pelican (BMW Part # 61.36-1 391 397, these are gray) and stuck them in when he restored the AC system after removing it for AutoX duty. He was two-thirds lucky.

Using that relay on the high speed fan caused big problems:

The burnt out connector is for the high speed fan relay. By using the wrong relay, the interlock that prevents the high speed and low speed winding from being turned on at the same time was defeated and the 30AMP fuse 41 was fed directly through the small gauge wiring feeding the relay control. So it burned up.

This connector was shot, I could not remove the burnt in pins and had to cut the connector out and splice a new one in.

For future trouble shooting and clarification, here is a diagram that details what relays go where, and what the pin functions are (this appears to hold for every year of M3, and may hold for all E36, YMMV, caveat emptor, don’t sue me etc. etc.):

The proper relays are

  • High speed fan BMW #61.36-1 391 397
  • Fan Clutch Relay BMW #61.36-1 389 105
  • Low speed fan relay BMW #61.36-1 389 105

Many thanks to Todd at the M3 forum for taking the time to give me the part numbers for the relays that were installed in his car.

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8 Responses to BMW E36 Air Conditioning Relays

  1. Don says:

    If the high speed relay functions as the interlock, how come the above diagram lists both the high and low speed relay to have Pin 30 fed from Fuse 30?

    Shouldn’t Pin 30 of the low speed relay say: “From pin 87a of high speed relay”?

    As that would mean when the high speed relay is energized it switches from pin 87a to pin 87 (which is the high speed winding) and disconnects from 87a, thus removeing +12v to pin 30 of the low speed relay.

  2. Don says:

    ^^
    Typo:
    I meant both listed as pin 30 being fed from Fuse 41.

  3. enderw88 says:

    Nice catch! I updated the diagram.

  4. Don says:

    Ah nice!

  5. Don says:

    Now unless some (US)spec cars have different wiring, now that I check the ETM I see more things. For example all pin 85 and pin 86 designations are reversed. 86 is fed from fuse 16 for example and pin 85 is DME (on AC relay).
    According to the ETM, stage 1 and 2 relays have no 86b pin, but 85b. The 85b on the stage 2 is listed as a (6th) connection to the DME (M3 only).
    Pin 85 (listed as 86) of stage 2 goes to pressure switch (as listed) but also to the temp switch (same as stage 1 relay) but at the other terminal of the dual-temp switch.

  6. enderw88 says:

    I did notice those differences when I was going through the wiring with the ETM in hand. The pin numbers were taken from the relays themselves, and didn’t match the ETM. These were actually continuity checks with the fuse box. If I have a few minutes this weekend, I will pull the relays and verify. The previous error was just a cut-and-paste mistake. I will need to re-verify on my car the other pins. It could well be that you have pointed yet another PO modification that I haven’t caught yet. Sorry for any confusion. I will try to get back to this ASAP.

  7. Don says:

    Don’t worry about it. I mean the ETM could also have a typo, which I hope not, as so far it’s been my “Bible” when retrofitting options. Sure would hate it if I toast some wiring because the ETM has listed a wrong pin number, but so far it’s been the greatest of BMW docs.

  8. […] the relays i say do not exist on my model are shown in the picture on this page, thanks !!!! BMW E36 Air Conditioning Relays | Mechanical Daydream Attached […]

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