Electrical Gremlins (Tach intermittent, Blower motor runs with key removed)

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  • amorphiss
    Noobie
    • Apr 2014
    • 10

    #1

    Electrical Gremlins (Tach intermittent, Blower motor runs with key removed)

    Anybody have any ideas what could be causing my issues on my E30? Specifically the car is a 1988 M3. I've owned the car since 2001 and it was bone stock with no wiring modifications when I bought it from the original owner's wife. It hadn't been run in several years and developed these issues in that downtime.

    Symptoms are that the tach on the instrument cluster is intermittent (usually gets stuck at an rpm - either 0rpm or 1000rpm) and occasionally jumps around. All other gauges seem to be working fine. OBC works fine. Additionally, while re-charging my A/C I found out that my HVAC blower motor continues to run even when the key is removed from the ignition. I replaced the batteries on the original SI board with external AA's, but no change in behavior. I bought a new SI board from BavRest and again no change in behavior, tach is still intermittent. I checked fuses 10, 20, 21 (and all others) and all were okay.

    Any ideas what else I should look for? Should I replace the coding plug on the cluster? What about the HVAC blower motor running with the key removed? I haven't been able to find a single thread on this forum or s14.net where someone had a blower motor that continued to run when the car is off.
  • Navarone
    Banned
    • Jun 2014
    • 935

    #2
    K6 relay is for the blower motor, check that.

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    • modernist
      Wrencher
      • Apr 2014
      • 283

      #3
      also relay K7 shuts off power to the blower when the ignition is off or cranking. my blower would stay on, replacing K7 fixed that.

      1986 327i
      transaction feedback
      DIY thing
      meh

      Comment

      • Gregs///M
        Forum Sponsor
        • Mar 2012
        • 2459

        #4
        Replace fuse 10, 12, and 21. Dont bother using 25+ year old fuses, they can cause intermittent power issues due to oxidation and micro cracks that can expand with heat and electrical current.
        Owner - Bavarian Restoration
        BMW and European Electronics Repair and Restoration
        www.BavRest.com
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