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Thread: The two thermosensors

  1. #1
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    The two thermosensors

    Hey there, you know how some of our cars have not one, but two thermosensors checking coolant temperature? A green one and a cream one? Well, both of mine broke.
    I managed to find replacement pigtails online, thankfully, but unfortunately, they are slightly different from eachother
    With the plug facing you and the clip on top, one has a notch on the lower left and one has a notch on the lower right.
    I think the lower left one is the odd ball, cause I can only find ones with the lower right notch online.
    Does anyone know what this is or what it does? Maybe that will help my search.

    It's an 86 Accord LXi automatic. I have the repair manual and can't find a mention of the second one.



  2. #2

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    Re: The two thermosensors

    You could always trim the notch off the one you can't find, just don't mix them up

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    Re: The two thermosensors

    Yeah I was thinking that. It probably is the same mechanics, just as long as the same wires are connected. I'm still curious what the difference between them is. Does one happen to deal with cold start settings? Cause that started to be a problem after I noticed one was broken.

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    Re: The two thermosensors

    I would have to see which ones they are before I can tell you from the manual, I don't have an efi car

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    Re: The two thermosensors

    https://www.3geez.com/forum/showthre...-Clarification

    This might help you but Im sure the 86 fuel injection has some different sensors than all the latter year cars.
    1988 Lxi owner since August 1995
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    Now running E85.

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    Re: The two thermosensors

    If its the white cooling fans plug that one is on every car, you can go to a parts yard and find it on a lot of hondas. On the earlier carbed cars the sensor is in the bottom of the radiator

  7. #7
    LX User AWH's Avatar
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    Re: The two thermosensors

    One of them indeed affect cold starts, or starting in general. Because it reads wrong temp., the fuel mixture is set wrong as well, hence the bad starts. Not sure which one though, but you will have to replace both anyways, so that should solve it.

    Verstuurd vanaf mijn XQ-AU52 met Tapatalk

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    Re: The two thermosensors

    This is one of the sensors. I believe the cooling fan one which is very common.

    https://smile.amazon.com/gp/product/...?ie=UTF8&psc=1


    Here may be the cold start sensor - closer to the engine block
    12021 Tomco
    search for it on ebay there are a couple for sale.
    https://www.ebay.com/itm/40182588127...kAAOSwgn1dOJ8p
    Last edited by conozo; 09-27-2021 at 09:51 AM.

    1988 Honda Accord LSDX-I

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    Re: The two thermosensors

    This was a couple weeks ago, but just an update. Ended up cutting a notch out of one of them, and it fired right up! Even after sitting for a month. Startup issue was definitely due to the thermosensor.
    However, my new cooling fan still doesn't turn on when the engine gets hot. The old one didn't either, and was just hotwired to be "always on".
    I guess its something else.. gonna hotwire it again..
    https://imgur.com/a/PFTOzTt

  10. #10
    LX User AWH's Avatar
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    Re: The two thermosensors

    Told you, glad it starts again. Just replace both sensors, and it will start and run the fan as well too.

    Verstuurd vanaf mijn H8314 met Tapatalk

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    Re: The two thermosensors

    Was away from my honda for a while (got a shuttle bus?!?) but returning now to further explore the temp gauge/fan situ.
    Are there some good aftermarket alrternatives to our thermosensors? I'm not talking about the ones I just replaced pigtails for, they seem to be working, but the one on the radiator that's supposed to control the fan. I still get relatively low temperature readings, even tho the car is fully warmed up. I'm probably going to add a switch to turn on the fan whenever I want, but it would be nice to get an accurate temp gauge.

  12. #12


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    Re: The two thermosensors

    Quote Originally Posted by profquad View Post
    Was away from my honda for a while (got a shuttle bus?!?) but returning now to further explore the temp gauge/fan situ.
    Are there some good aftermarket alrternatives to our thermosensors? I'm not talking about the ones I just replaced pigtails for, they seem to be working, but the one on the radiator that's supposed to control the fan. I still get relatively low temperature readings, even tho the car is fully warmed up. I'm probably going to add a switch to turn on the fan whenever I want, but it would be nice to get an accurate temp gauge.
    It seems this comes up alot from my memory but I dont know if its the switch or the controller under the passenger seat.

    Other thing I questioned from one person was whether the replacement radiator was getting coolant to the sensor.
    1988 Lxi owner since August 1995
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    Now running E85.

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  13. #13
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    Re: The two thermosensors

    Are you sure the thermostat is nit stuck open That could expand the low temps also.

    Verstuurd vanaf mijn XQ-AU52 met Tapatalk

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    Re: The two thermosensors

    Quote Originally Posted by conozo View Post
    This is one of the sensors. I believe the cooling fan one which is very common.

    https://smile.amazon.com/gp/product/...?ie=UTF8&psc=1


    Here may be the cold start sensor - closer to the engine block
    12021 Tomco
    search for it on ebay there are a couple for sale.
    https://www.ebay.com/itm/40182588127...kAAOSwgn1dOJ8p
    My friend might need to replace the cold start sensor on his new '86 Accord project. We'll take a look after we finish installing the brake pads and cragar wheels on the truck and clear the garage.

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    Re: The two thermosensors

    Quote Originally Posted by AWH View Post
    Are you sure the thermostat is nit stuck open That could expand the low temps also.

    Verstuurd vanaf mijn XQ-AU52 met Tapatalk
    Yeah, early on in this process I replaced the thermostat, but it made no change. The AC fan comes on 20 seconds after turning off the car, so I know some part of it knows it's hot, I just don't know who isn't telling the main cooling fan or the temp gauge.

  16. #16
    LX User AWH's Avatar
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    Re: The two thermosensors

    Replace both, small cost, and be sure of them working.

    Verstuurd vanaf mijn H8314 met Tapatalk

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