Problem: Honda running very hot and the radiator fan never turns on.

 

On the later model Hondas the electric radiator fan is controlled by means of a relay, which in turn is activated by a thermo sensor.

The following is a procedure to use to determine why your fan does not turn on:

 

Check fuses

Be sure to check both fuses that control the radiator fan.

The current going through the fuse under the hood goes through the relay contact and the fan. The current through the fuse under the dash goes to the thermo sensor and relay coil – this current also goes to other places in the car.

Fan Check

Start the car and turn on the AC (if so equipped). Both fans (AC radiator and regular radiator) should turn on.

If the radiator fan is not turning on, the relay, wiring or fan motor is bad or power is not getting to the fan relay. 

Turn the AC back off before proceeding.

 

Thermo sensor check

Short the contact on the connector going to the thermo switch to ground. This connection goes to the fan relay.

 

If the fan turns on, your thermo switch is most likely bad.

 

If the fan does not turn on and the fan was not turning on with the AC running, your relay may be bad.

 

 

Relay check

On most Hondas, both the AC fan and radiator fan relay are identical parts. Inspect both and make sure this is true on your car.

 

If your relays are both identical, swap the AC fan and radiator fan relay.

Turn on your AC and see if your radiator relay now turns on.

 

If it does, your radiator fan relay was most likely your problem.

 

Of course, since you swapped the relay with the AC relay, the AC fan is most likely not working now. Be sure to replace the correct relay when you get your new relay.

 

If you don’t have a replacement relay handy, you could leave the swapped relays like this until you get around to getting the relay from your favorite mail order place or dealer.  Be sure to not run your AC until you get the replacement relay.

 

If the radiator fan still does not turn on, your problem is most likely within the contacts to the relay socket.

Turn your AC and ignition switch back off before proceeding.

 

Check relay socket contacts

Using a small screw driver, carefully bend all connections on the relay socket to the middle.

These are pinch type connections and we want them to make good contact with the relay.

Put the relay back and retest.