I have a 99 Accord Ex 4 cyl sedan. Cooling fans are not turning on at all, causing overheating in city driving. I have jumped the fans directly to the battery and they operate properly, so I replaced the cooling fan switch (thermo switch A in the thermostat housing.)

The fans are still not coming on. Does this car have a fan control module that the switch signal goes through to tell the fans to turn on? Is there a way to jump the switch itself?

Thanks in advance

 

Do they come on when you turn on the A/C?

 

No, but the a/c doesn't work. An electrical issue that started last summer. (When turned on, the compressor doesn't engage, so I assume it's electrical.)

 

The first diagnosis would have been this...
Unplug the fan switch (in the thermostat housing) & jumper the wire with a paperclip. Key on, that should make both fans run. I'm guessing it doesn't, which should have told you the fan-switch wasn't the problem.

There's no fan-timer module like there was in earlier years. There's only one fan switch & it's on the T-stat housing.

 

I jumped the fan switch and the fans turned on. Wouldn't that mean it was in fact the switch (which I just replaced)? I'm a little stumped.

 

Also, just drove the car around a bit to see how it performed. Temp gauge started to climb at idle. I parked the car with it still running and jumped the switch again, turning the fans on. Gauge stayed at 3/4 even with fans running.

Could it be as simple as the thermostat? I will try that and see if it works. If so, I will feel really stupid.

 

OK, you might just have to wait for it to get hotter. Temperature gauge at 3/4 might be close to the point where the fans come on. The gauge WILL go higher than 1/2 before the fans turn on, but not sure how high it has to go.

When you originally said it overheated, I thought you meant the gauge went higher than 3/4.

 

Er, so it was the thermostat. Stuck closed, the coolant wasn't getting heated in the engine block to activate the fan switch.

First things first, genius. Oops!

 

Geez, I'm usually the guy who says to check the easy simple stuff first. Thanks for coming back & telling us the fix.