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What temp switch for front fan??



My block switch ( I don't know what the hell you call it) is kaput. It won't ground out and start the front fan. What temp do I want? I'm thinking about 170 or so. Does the a/c run the inside fan or the outside one? Thanks.


Well-known member
Dec 31, 2002
1986 Pace Car
Does your car have one or two fans?

If two fans (auxillary fan), you will have a fan switch (sensor) threaded into the driver's side cylinder head between the two front most spark plugs ( plugs 1 and 3). Looks like this:

The other single green wire sensor on the passenger side cylinder head near the oil dipstick is the one that sends the coolant temp reading to your instrument cluster guage inside the car.

This is the coolant temp guage sender. On the '86 it's on the passenger head.

If only one fan, you will have a pipe plug with a square hole on the driver's side head instead of the fan switch in the very first picture. Looks like this:

Here is how the cooling fan control works and how to troubleshoot.

Read this:

Click Here

Check the cooling fan relay:

The cooling fan relay is here.

Unplug the relay, and connect a wire between the outer left and outer right terminals of the connector with key on and motor off. This gives direct current to the fan bypassing the relay. It simulates the relay in the closed position which happenes at about 230 degrees. If the fan runs, the fan is good. The relay is probably not closing.


Bend a paperclip into a U shape and insert it between the two upper right hand terminals (A and B) of the ALDL connector. Then turn the key on with motor off. The fans should run and stay on untill you remove the clip or switch the key off.


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