Cooling fan won't turn on!
 

Hey guys I have a 1994 accord ex. The cooling fans won't turn on when the car gets hot at idle. I already replaced the thermostat, radiator fan switch, and the engine coolant temperature sensor. Fuses are good. I can get the fans to turn on when I jump power to the fan switch connector. Thy turn on with the AC on. But it wont turn on as it should when the car starts to overheat.

Check the coolant level. Also, these are very picky about air in the system so you need to be sure you bleed the air from the cooling system using the proper procedure.

There is a bleeder valve on the t-stat housing that you have to use along with a few other proper steps.

Try removing the connector for the thermoswitch A (near thermostat housing) and jumpering the connectors w/ a wire. W/ keyswitch to ON, the fans should run.

The only reason fans would run w/ AC on and not run w/ AC off is lack of ground through a closed thermoswitch A or defect in wiring to/from thermoswitch A to ground, or missing ground connection. Check G101 ground on firewall near brake fluid reservoir.

good luck

How can you tell if there is a bad ground?

Loose, rust, corrosion present.

First check thermoswitch A by jumpering the connector (harness side).

good luck

When I jumper wires directly to the connector for thermo switch a ontop of thermostat, both fans kick on.

Then you have a faulty thermoswitch A or perhaps you have a faulty ECT sensor and car is not really overheating.

A IR temp sensor should be used to confirm car is warming to about 194F w/ thermostat and engine fully warmed. Wrong thermostat would prevent car from reaching proper operating temp (usually just below horizontal on temp gauge).

In my experience, the fans rarely come on w/o AC as long as car is moving. If you stop in traffic for very long in summer, temp will begin to creep upwards.

good luck

I have replaced thermo switch A, the ECT, and the gauge sensor. It overheats when it sits and is running. Went to smog it and temp was getting too hot he had to void the test. The fan should come on and cool the car down when the temp gets to hot correct?

Yes, thermoswitch A is likely fault despite it's being replaced.

However, ECT could be faulty also. Have you cross-checked w/ IR temp sensor?

good luck

I replace the thermo switch a 2 times. With brand new parts . How do you cross check wires?