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Discussion Starter #1
hi All,
My daughter's Celica's temperature gauge is acting up since installing a new radiator.. It shows cold barely moves up off the bottom of the gauge.After driving 20 minutes on the highway it moves up a little more. If idles longer it moved up to be what I would think is normal. See two attached pics. I want to change the coolant temp sensor and I am pretty sure its one of there two sensors but I am not sure. Any advise which one it is? Is it both? How do I check them? They are cheap I would just replace them... thanks for the help!
 

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Sounds like the fan is on all the time. The fan switch is probably what you are pointing to. My documents are for 1995 but should be close for your car. I think it's light blue single pin connector. If you unplug the switch, the fan should be on all the time. If you take a wire and ground the pin, the fan should be off. The switch should have continuity to ground below 181F and go open above 194F. Switch does fail, I've replaced the one on my car before.

Another test is that possibly the sensor going to the gauge is bad. That is a switch with light blue/yellow single terminal. That switch will have continuity to ground. 122F is 160-240ohm and 248F is 17-20ohm. That will give you an idea what the sensor should be reading.

An infared laser gun can be helpful if you think the engine is getting up to temp. You can measure metal temp at the thermostat housing or head to confirm if the engine is actually getting hot or just staying cool. If the engine is actually staying cool, it could be a thermostat held open.
 

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Thanks for the reply in info. I replaced the coolant temperature sensor and it shows a little bit more accurate response to driving vs stuck in traffic. If idling for a long time the gauge goes up to what I would think is normal temperature. As soon as I start driving it drops down so the radiator is doing that it should be doing. I am guessing open thermostat as well, I will replace that and see what happens. Thanks again...
 
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