90 CRX DX. I replaced the temp sender and the temp gauge maxed out. Pep Boys sold me the unit and come to find out it was an oil temp sender they sold me. It screwed in and the plug connected. The only way i could tell was that the box said "oil sender". I replaced it with the "correct" part but the gauge has been acting strange. After starting the car cold the gauge will move up faster than usual and sometimes fluctuates or runs hot. I think the gauge got messed up when the wrong sender was used. Is there a sure fire way to check if it is actually overheating before buying a new cluster? P.S. It doesnt show any symptoms of overheating. Fan comes on. Both hoses will be warm after driving. Thanks

 

well if your fans come on, means the car is getting warm and the fan switch is reading the signal and working which is good. Coolant temp sensor (which runs the guage) is moving the needle in the car so it is sending some sort of signal. The fact that the upper and lower hoses are warm, makes me believe that the thermostat is opening and working right. However it could be partially opening and it would be hard to tell that. When the fan comes on does it stay on or go off after some time? If the fans go off and the temp is still reading hot i would say try another coolant temp sensor. If they stay on and dont go off and the temp is reading hot i would play it safe and say the car is overheating.

 

Fan doesnt stay on and it has a new thermostat.

 

Maybe air bubble in system. Burp it.

 

so i doubt it is actually overheating, it may be an air bubble in the system, or a bad coolant temp sensor. I would try a new one.