My electric fan (factory single fan on '87 LT 305 car, now running a 327) kicks on when the A/C is switched on, but it won't kick on otherwise, even when the engine is hot.

By reading the cooling sticky at the top of the forum, it sounds like the switch which turns the fan on is located on the passenger side of the engine. Can anybody give me a little more detail as to its location, or even a picture? There's a switch or sensor located on the passenger side of the block, near the starter, and I'm wondering if that may be it. I wasn't sure if that was the temp switch or the knock sensor.

Also, is the temp switch for the electric fan also the sending unit for the temperature gauge, or are they separate?

My factory temp gauge is reading max (pegged) all the time. I'm wondering if it may have lost a ground connection or something. Anybody else experienced a pegged temp gauge?

Thanks in advance

 

Is it possible you have the pigtails switched on the temperature sensor and knock sensor?

 

The temp sensor for the guage on the dash is on the drivers side head toward the front of the head, The fan switch is on the passenger side head toward the back of the head, actually both sensor are in the same spot on the head just different sides of the engine.

What heads are on the car? early or late model SBC?

Also you can simply ground the wire going to the fan switch and the fan should come on.

 

Is this true on all years? I have a 1991 and I do not recall seeing the guage sensor on the drivers side head. My guage is not working either, so I am now curious.

 

If it is maxed even when the car is off, it may just simply be stuck on the edge of the gauge face. Key on, engine cold and a light tap to the cluster may free it.
The gauge will max if grounded. At start (crank-cold), the gauge ground through the ign switch and should max. Once the key is let off to the run position (engine started) the gauge should go back to minimum temp and read as usual.

If they are in the factory locations, no. The harness plugs are different even if it was possible.

Yes, for v8, unless there is a mechanical (belt driven) fan. Then, there is no fan switch.

 

Great info, guys -- thanks for all the replies so far.

It has early small block heads from a 1971 350 (76 cc) w/accessory mounting holes on the front of the heads.

The gauge is pegged to max all the time, even with the key off.

There is a sensor mounted in the passenger-side head, but the sensor isn't connected to anything. It has a single male spade terminal on it. Would this be the fan switch? So that I can try to find the wire that should be connected to it, can somebody tell me where in the harness this wire should be coming from and what color it is?

An aftermarket temp gauge has been installed at some point since the factory gauge didn't work, and the sending unit is mounted in the water neck (poor location! -- doesn't read anything until the thermostat opens **if** the thermostat opens).

 

By looking at pictures of the coolant temp sensor and coolant temp sending unit on Rock Auto's site, it looks like what's mounted in the passenger side head is actually the temp sending unit, and I don't know where the coolant temp sensor / fan switch is located.

 

if you have a tpi motor the fan switch is on the passenger side on the intake manifold it has the same connector as the air temp sensor

 

A spade terminal would suggest it is the temperature gauge sender. This should be in the driver side head.

The wire for the fan switch will be on the drivers side ans should have a similar harness plug to the knock sensor.

The water neck (thermostat housing) is where the original coolant temp sensor would have been mounted.

This is 100% wrong. You have described the coolant temp sensor as they are the same sensor.

The fan switch for ANY v8 motor is located in the passenger side head.

 

Should be right above the starter motor. Between #6 and#8 spark plugs.