My radiator cooling fan is not switching on at all when it gets too warm. I went direct from the battery to the fan and the fan worked fine. I replaced the thermo-switch, but still no go. I cleaned the connectors as best I could too. Is there anything I'm missing?

 

I took the radiator cap off at normal operating temperature, accelerated it and the flow seemed o.k. Could a bad flow from a bad thermostat cause the fan to not turn on, and what temp should a new thermostat be rated?

 

thanks for all the help

I ran into the same problem on a subaru hatchback I used to own.I ended up having to hook it through the negative side of the battery so when the relay temp sensor got hot enough then it would complete the circuit.I had the pos + always connected and then ran the switch side throught the neg - side.Hope this helps.I believe someone did a write up on this.At the time when I did this I had to do it by trial and error.

same here my 83 hatchback had same problem, i just rigged it, so when the car is on it comes on, beacuse everything else i tryed didnt work and i kept over heating, so it works now, havnt had a problem yet lets see how it does in the summer

This is how I figured out problems with my '89 EA82 aux fan.

 

Disconnect the thermoswitch.

On the harness side connector, jam a paper clip in to short the two contacts together. This is basically what the thermoswitch does when it gets hot. Turn the ignition to acc or start. Fan should come on. If it does your thermoswitch is still bad or rated too high. If the fan doesn't come on, get out your multimeter (voltage/resistance) and measure the voltage on the two contacts (same connector) to battery (-). One contact should read 12V with the key on acc. Switch your meter to resistance and measure between the other contact and battery (-), should be low 25 ohms or so.

 

Hope this helps.

I think there is a relay in the circuit that may be the fault here. The thermoswitch turns on the fan relay I believe.

I thought I had read somewhere around here that one reason these thermo switches failed rather frequently was that there is NO relay, that the switch takes the whole load. Is that wrong? Certainly they would last longer WITH a relay, than without.

 

Pyro