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CHTS Test Results

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  • CHTS Test Results

    So my car started running abnormally rich after installing several electrical pieces including an ECU, a engine harness, and a CHTS. I checked connections, then ran the codes. The code for CHTS came up. I pulled the CHTS and subharness and tested them as described in the 84 FSM on EF & EC-46. A fluke multimeter was used to measure resistance, and a craftsmen multimeter to measure temperature.

    When the water reached boiling, i dropped in the CHTS and both probes. Neither the probes or the CHTS were touching the pan. The water was held at the temperature points for long enough for the resistance measurement reading to stabilize, which usually took 10-20 seconds. Temperature is measured in Farenheit, and resistance is measure in ohms.
    Actual Results

    These measurements are all close to FSM specifications.
    FSM Specs


    While 3 of my test results are in range, they are all on the low side. The data point for 68* is lower than the specified range. How close do these measurements have to be?

    So what do you think? Are these resistance measurements close enough to factory specs? Is this CHTS and Subharness bad, or is the problem elsewhere in wiring harness? As i mentioned before, I just installed a different engine wiring harnes that i had trimmed back (non-existent emissions equipment and others) and re-loomedfor a cleaner look. Tomorrow, provided you all think that my CHTS is fine, I will reinstall it and test the engine harness at the 16 pin ECU connector as described in the FSM on page EF & EC-46.

    "produce second."

  • #2
    My understanding is that sometimes when thermistors fail, they simply read substantially off on one or both ends of their resistance (temperature) range. I would guess that the low temp end seems to be a little off, but it does not seem too bad. You said it was running rich when the car is warm, right?
    You should be able to measure the resistance in the subharness alone very easily.
    I might have another CHTS sitting around for you to give a try...


    • #3
      The car runs rich. When cold it has trouble starting. When warm it blows black sooty smoke. There is black soot on the garage floor behind my exhaust :shock:
      I believe the problem lies in the harness. My old harness was all hacked and taped up. It looked bad and had a bunch of plugs on it i wasnt using. So, I bought a harness from member John Blye (SP?) and reloomed the whole thing. I intsalled it and it looks really nice, and I was very happy with it until this problem. The problem occurred 2 days after installing the harness. A simple resistance test will tell me whether the harness is the culprit or not. If the harness reads normal resistance, then i will replace the sensor. Since the car runs rich when warm, and the sensor is within specs when warm, i suspect the harness. A bad ground or cracked wire is my current guess.

      Its freezing cold outside right now, and more snow is on the way for west michigan. I'm going to take a look at it when i get some free time to bundle up and fire up the salamander!

      Thanks Jason
      "produce second."


      • #4
        when warmed up the engine should only be in the middle of that range so the middle two numbers matter more than the edges....

        212 is boiling and unless you race you shouldn't get that high to worry, and regardless the ohms is showing low so the 212 sensor for a condensor fan would kick on earlier not later (if it was _that_ sensor)

        if anything the whole range suggests the ecu thinks the engine is warmer than it is, and the ecu enriches when cold....