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Thread: Otterstat testing

  1. #1
    Junior Member
    Join Date:  Jul 2016

    Location:  Colton, CA

    Posts:    25

    My VIN:    5368

    Otterstat testing

    Has anyone done testing on an otterstat as far as resistance measurements at different temperatures?

    I suspect mine has failed (fans only come on if I short the prongs, coolant level is full). I installed a new one back in the end of 2016. Not sure if their life is that short.

    Will the otterstat measure close to zero ohms when fan temperature is reached? I realize is a cheap part, but I would like to confirm it as the culprit before I swap in a new one. Thanks guys..
    Vin 5368. October 81 Grey Manual

  2. #2
    Senior Member
    Join Date:  Oct 2016

    Location:  San Diego, CA

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    My VIN:    10353

    What about just jumpering it to see if the fans kick on. If they did wouldn't that point to it being faulty and then needing replacement?

  3. #3
    Delorean Guru
    Join Date:  May 2011

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    The "O" switch is just an on-off switch. It should only show 0 ohms or infinite ohms. If it shows anything other than that it is NG. The only "test" would be to check for continuity when cold (there should be none) and if you heat it up in hot water it should show continuity at around 180 degrees. Not really necessary to do that. You can test it in the car. When cold the fans should not run. If you jumper the connections with a paper clip the fans should run when you jumper the wires with the motor running. When the motor warms up the "O" switch must turn the fans on. You can watch your temp gauge or use an IR thermometer to see how hot it is. If you replace the "O" switch you should also replace the seal. You MUST use either the clip or a strap tie to secure the "O" switch. Make sure you have the uprated circuit breaker for the cooling fans and nothing is melted and you have bypassed the fan fail relay. Refer to ST-27-11/81 and ST-06-9/82. If you have an early car the pipe must be modified to mount the "O" switch on the bottom of the pipe so an air bubble can't prevent the "O" switch from sensing the coolant temperature.
    Last edited by David T; 11-27-2018 at 02:20 PM.
    David Teitelbaum

  4. #4
    Junior Member
    Join Date:  Jul 2016

    Location:  Colton, CA

    Posts:    25

    My VIN:    5368

    Great info I will give that a shot! thanks everyone for the help!
    Vin 5368. October 81 Grey Manual

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