So I have a 2000 ap1 and having issues recently. Background I have 145k miles. All stock except mishimoto radiator with stock fans. I just noticed my fans don't turn on after being warmed up. Gauge says 3 bars what it should be and fans turn on when AC is on. I just replaced my engine coolant temp sensor (behind) manifold after throwing a p0116 and hasn't came on after pulling fuse to reset ecu. Before replacing the sensor it never over heated or showed more than 3 bars on gauge cluster. But now I noticed the issue with the fans. Is there another sensor or something I have to replace or something? Possibly air in the cooling system?

 

Are you sure the fans came on before when the gauge read 3 bars? Maybe the engine was not hot enough for the ECU to ground the fan relay.

 

On early cars the radiator fans are controlled by a separate temperature switch (on/off) that is mounted in the bottom of the radiator. They can also be controlled by the ECU but normally it's the radiator switch that makes the fans cycle on and off. Maybe that switch is bad or maybe the combination of seasonally lower ambient temperatures and your (I assume) larger radiator is keeping the coolant temperature below the switching point, which I think is 200°.

Note that 3 bars on the gauge covers a disgustingly wide temperature range from 160° to 235°, so the car could overheat by 20-25° and you wouldn't know it.

 

Thanks for the input. I guess it just took awhile for it to start. It comes now for a a couple secs and turns back on. Must be the bigger radiator. Probably never paid attention until now since I changed out my sensor. So I after 400 miles of driving CEL came on again for p0116 again? I just changed that sensor behind the intake manifold. What's going on?! Should make another thread?

 

at idle it takes a while for my fans on my 01 to turn on. 2-3 minutes (never overheated)

 

Could there be air in my cooling system? I have not changed coolant or anything. I do have a small leak on top bp by the fill cap above where the overflow hose is located. Could that be the issue?

 

So my buddy works at Honda and ran diagnostic on it. All coolant temp and sensor reading are normal ranges. Might be air in the coolant system. Going to fix my little leak and bled the system correctly at Honda next week. Hope that works. If anyone has anymore ideas or suggestions feel free to chime in. Thanks