Rep Power: 0

Hello everyone,
Have an 03 Honda civic ex coupe that fans turn on, before ignition. Turn off after i take the key out. I replaced the cooling fan switch and they turned off, but then wouldn't turn on, and the car started overheating. Replaced it the first time with an aftermarket part, then a OEM part, same result. So put the original back on and they turn on, but before ignition and stay on. Worried fan motor will go out or poor gas millage. Any input would be appreciated, thanks!

 
Rep Power: 517

Sounds like multiple problems.

First fan switch sounds bad, shorted internally so fans run all the time

Then you discover that with a good switch installed....Engine overheats before fan switch reaches temp to turn fans on, maybe due to low coolant level or air pockets or flow problems or.....head gasket blown.

Boiling water test the new fan switch to make sure it will close its contacts, then proceed with the usual overheat diagnosis?

 
Rep Power: 0

Thanks for the input. I will check out the new fan switch. I have already replaced the radiator, hoses, water pump, radiator cap, and thermostat. I have flushed the system and bled it. I've checked the pressure and have seen that the pressure drops, but only slightly. I have seen no leaks, externally. I also have not seen any blown head gasget symptoms ( milky oil, white smoke). The car hasn't overheated and runs fine, but the fans are always on. Will try to do a compression test and see if anything shows up. I pray it's not the head gasket lol.

 
Rep Power: 221

put shop air to the cylinders and see if you get bubbles out from the rad cap or the level increases

 
Rep Power: 517

This engine does NOT give any of the symptoms most people look for. This engine can and will pass every test most people can think of, while the blown head gasket issue is relatively minor.
It has to be blown really freekin bad and maybe have a warped head before any "usual symptoms" that most people look for would ever be seen..

Colin42 told you how to prove the head gasket.
Locate the overheating common causes sticky thread, contained within the first post is a video of that test that reliably proves a bad head gasket on this engine and tells which exact cylinder(s) have the problem.
You said in the first post that it overheated while it had a new fan switch installed, yes?
What did you see that made you say it overheated?

The constantly running fans may only be covering up the overheat problem.
This will not reveal a bad head gasket on this engine.
You just jinxed yourself. Now it's guaranteed to be.

 
Rep Power: 0

Quick question to add to this thread... should my fan be turning when car is in neutral and idling? I have a manual trans.

 
Rep Power: 517

ONLY if the AC compressor is on and/or the coolant temperature is hot enough to turn the fan switch on.

Otherwise, no. Not until the above condition is met.

 
Rep Power: 0

okay thanks, what if I rev the motor while its in neutral, will it turn then? Or do those conditions still apply?

 
Rep Power: 517

These are the only conditions that make the radiator fans turn on, this is all that the computer is looking for to run the fans(*):

*when everything is working as designed, 01-05 D17A1 and A2 engines