I have a 97 Civic, It has been overheating for the last month or so only while city driving never on highway. Can control it by using heater for the most part but it still can get very close to HOT somtimes. I have read alot of related postsand have come to this conclusuion. When ac is on only ac fan comes on. I have jumpered the CTO switch in the thermastat housing and cooling fan kicks on. I have replaced CTO switch and still get no power to coolong fan,even with a/c on.Any sugsetions on what to trouble shoot next would be great.
Thanks
John

 

My guess is that either the new ECT switch is bad or the wire harness connector is not making good electrical contact with the ECT switch connector. If you are sure the replacement ECT switch is good (see picture), then inspect the connectors for corrosion or damage.

 

I think the 92-99 Civic has a side by side radiator and condenser, instead of in front of each other like most cars. The two systems are independent. The A/C fan is only for the A/C. The radiator fan is only for the engine. Turning on the A/C is not supposed to activate the radiator fan.

Try driving with the switch jumpered so the radiator fan runs all the time; if the engine doesn't overheat it is definitely something with the switch. Maybe you got a bad one or it's not making good contact.

 

This is correct.

 

Thanks for the info. I thought turning on a/c was supposed to activate both fans. It def has side by side setup. I was using this theory (wrong) to test fan after replacing switch. I never saw fan kick on even when temp seemed to raise a little. I did top rad of with water when done. It seemed to take in more than was lost while working on it.Drove last night and this morning, even though a little cool outside the guage didn't budge once up to normal temp. Normaly it does. Maybe Its working fine, I'll give it more time & see.

 

When the engine is cool, first be sure again to top off the radiator and reservoir. It's important to use coolant rather than water in the cooling system to avoid engine corrosion. The fact that the temperature gauge is not indicating a heated engine suggests that the thermostat may be stuck open.