Noticed my car kept wanting to overheat unless I was moving. Installed a new thermostat (didn't have one), still wanted to overheat. Noticed if I turned the ac switch to ON, the fan would come on and the car would run fine. Read the threads and the next thing is to replace the cooling switch, the switch that tells the ECM to turn ON the fan because the water temp is too high.

My question is.. Is this the switch....? I'm standing over the passenger headlight when I took this pic, and as you can probably tell, it's right next to the thermostat inlet.. any help as always is greatly appreciated!

Stone (this is for my gals 91 RS 305 5 speed )...

 

Yes, That would be your temperature switch, but I think the temp sensor on the side of the block controls the fans. But I might be wrong, I get those two sensors mixed up

 

my temp sensor is on the intake in that location. the temp sendor for the fans is in the passenger head towards the back.

 

I thought it was on the drivers side, I think the knock sensor is on the passenger side

 

Can we end this thread of "I Think". Geez, really get the poor guy confused.

Here's the REAL DEAL...

What you have pictured - it should have 2 wires, yellow and black - that is your COOLANT TEMPURATURE SENSOR. It relays coolant temp readings to the ECM.

The ECM controls your primary fan, and turns it on somewhere about 218 degrees.

In the head, PASSENGER SIDE, between # 6 & #8 spark plug is your FAN SWITCH. It controls the secondary fan, and turns it on at 238 degrees. Has a single wire, with a weird mushroom-looking connector on it. DO NOT CONFUSE this with the KNOCK SENSOR, which is also located on pass side, but lower in the block rather than in the head. Knock sensor and fan switch have the same mushroom connector.

Now, the A/C will also turn on the secondary fan regardless of any temperature.

Last thing - DRIVER SIDE HEAD, between #1 and #3 spark plug - that is your COOLANT TEMPURATURE SENDER for the GAUGE - has a single green wire, and all it does is send info for the gauge in the dash.

 

Ok, thanks guys for your help. Thanks Camaronewbie, as detailed as I tried to be, I left out that the car is a single fan radiator. I'm thinking if I replace this switch the fan will come on when it suppose to. I bought the car for my gal, and just want to give her something a little more reliable than what she's driving now.

Stone

 

Yes, replacing the fan switch should make it work the way it was designed as long as the relay and fan are good. Easy to test, if with the key on or engine running you turn on the AC the fan should run. If so, your relay and fan are good. Lots of different fan switches with different temps for turn on settings. Do a search on the cooling forum for tons of discussions on them

 

Ok, replaced the switch in the pic. Fan still didn't want to come on above 220. Waited for it to get close to the red then put the ac switch to ON and fan came on and temp came right down, now onto phase TWO ! ( but loving every moment of it!)

Stone

 

the pic was of the temperature sensor for the ecm. the fan switch is on the back of the head on the passenger side. between the last 2 cylinders.

 

Try not to let it get close to the red, not good. Get that fan going by the time it gets up around 220 if possible. Fan switch is much easier reached from underneath and expect lots of coolant to come out so wait til it cools off. Have fun!

 

238° was the only temp for TBI fans (fan switch controlled only), it's not going to hurt the engine to get that hot. These aren't '60's motors running on leaded gas.
My '91 beater is getting ready to turn 218k... stock cooling.