420A Fans only coming on when thermostat reads hot

[TallyTheTalon]

Hey! I drive a ’96 Eagle Talon ESI, the only thing done to the engine is a cold air intake. I blew a heater hose not to long ago and the engine overheated for a very small amount of time. I replaced the heater hose and everything worked fine until I noticed my temperature gauge in the car was reading totally hot, no engine lights came on and my obd2 scanner was only saying the coolant was at 210 degrees.

The car drives perfectly fine now and never overheats, it's just the temp gauge in the car is reading as if it is overheating. The fans only turn on when that temperature gauge starts to read completely hot despite the fact that the engine is really at normal operating temperature.

I’m wondering if anyone else has had this issue that I’m having, if so, what did you to to resolve it? Would it be easier to find the root of the problem, or just wire the fans to a switch in the cabin of the car?

I’ve only had the car since October of 2022 and I’m located in Minnesota which means I haven’t driven it on 85-90 degree days, only below 50 degrees.

 

[Sirius1995]

so another fan is for your AC and another one is actual fan, and how your fan works is ones coolant temp get's in the operating temp, it will kick off the thermostat (temperature when it opens variates depending which thermostat you have) and when that happens, your fan will start rotating automatically to control the temperature, 210'F is good reading, as long you actually have coolant in the system, I don't think you don't have to do anything with your fan, sounds like it's working normally and doing it's thing, for your gauge, I think problem is in your cluster, so does it always stay up or does it gradually go up as you drive? does it go all the way down after engine has cooled off?

 

[TallyTheTalon]

For your gauge, I think problem is in your cluster, so does it always stay up or does it gradually go up as you drive? does it go all the way down after engine has cooled off?

Thanks for the response! the needle always stays in the middle when driving, it’s only when sitting and idling when the needle climbs, the second the needle reads hot, the fans kick on and the needle drops within seconds

 

[Sirius1995]

Thanks for the response! the needle always stays in the middle when driving, it’s only when sitting and idling when the needle climbs, the second the needle reads hot, the fans kick on and the needle drops within seconds

oh okay, I'd start with changing your coolant temp sensor and flush your coolant, and make sure there's no air in the system, that can cause that, and maybe even thermostat, who knows how old is that one and when it gives up

 

[BLACK'98DSM]

There are 2 coolant temp sensors. One smaller sensor which is for simply sending a reading to the gauge cluster, and one larger sensor which is for sending a value to the ECU. I would start by replacing the smaller sensor because its cheaper, easier to find, and more likely to cause the issue than the other one. If your gauge is truly providing a false H reading, then you can rule out the fans as an issue. And although it's possible, I don't think a bad gauge cluster is your issue. If that were the case it would be showing a false reading more often and fan operation probably wouldn't alter the reading.

 

[TallyTheTalon]

There are 2 coolant temp sensors. One smaller sensor which is for simply sending a reading to the gauge cluster, and one larger sensor which is for sending a value to the ECU. I would start by replacing the smaller sensor because its cheaper, easier to find, and more likely to cause the issue than the other one. If your gauge is truly providing a false H reading, then you can rule out the fans as an issue. And although it's possible, I don't think a bad gauge cluster is your issue. If that were the case it would be showing a false reading more often and fan operation probably wouldn't alter the reading.

Thanks for your knowledge man, you’ve helped me out countless times with my 420a. I’ll try that out and hopefully it’ll fix the issue.