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High temps? Electric fan conversion & A/C button makes temp gauge JUMP!

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    High temps? Electric fan conversion & A/C button makes temp gauge JUMP!

    History:

    '91 318is owned for 10 years. about 6 months ago I swapped in a Volvo fan and removed the manual and electric secondary fan.

    This car has NOT been a daily driver for many years.

    About the fan swap: I wired it straight to the AUX fan circuit in the car. I believe its a 30A circuit, and it gave me control over turning it on and off by use of the A/C compressor button on the dash. Been working great... sorta.

    New Autozone/O'reilly brand water pump a month ago.

    Ran an autocross in 95deg temps - no real cooling problems (ran it with the A/C on).

    I've actually been driving it back and forth to work for the last three weeks, sometimes w/o the fan (a/c) on because I head to work at 7am and its in the 50's in the morning. Gauge stays where it normally is (just a tiny bit over 1/2 mark).


    Tuesday I noticed the temp gauge running half way between 1/2 and 3/4 mark. Thought it was odd... Wednesday its a little higher. Today it crossed over the 3/4 mark on the way to work, on the highway at 60mph.

    To alleviate, I turn the heater core on and get the gauge to drop and stay between 1/2 and 3/4.

    I play with the A/C button and notice that with it ON, the temp jumps immediately to 3/4, and with it off it drops closer to 1/2. Its immediate... i.e. an electrical issue of some sort.

    I also notice that turning on the HEADLIGHTS (which I have been since its dark now) will make the gauge RISE just a tiny bit as well.

    I can't decide if i need to troubleshoot a cooling problem / water pump problem, or an electrical problem.... or if maybe the gauge or sender is bad.

    Thoughts?

    #2
    Sounds like an electrical problem. I'd check the ground from your chassis to you engine. I had a similar problem and I monitored the engine with a temp gun. Temps were low and the gauge read high (beyond 12 oclock).

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      #3
      Most of the problems with temp gauge is due to bad SI board/batteries...check those first.

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        #4
        will do. I think the batteries are either original, or 8+ years old... I haven't messed with them in a LONG time, if at all. (can't remember).

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