im generally good with this stuff but im stumped. i do not have a sensor on the pass rear of the head. and i want to wire up a fan switch. the one on front drivers side head is for gauge. i started the car and unplugged every possible AC wire that i could find, and the fan didnt turn on. i found the middle relay on the drivers side to be the coolant fan switch relay, correct? i spliced the green wire into my switch, and the fan still didnt turn on. now. here is where im stumped... the fan...kicks on on a regular basis. it heats up to 233* or whatever, then the fan kicks on, ALL the time. so i know there is no problem with the system, im just having trouble finding a place to cut into it.

im gonna go from one end of the fuse, run it to the switch, then run it from the switch to the other end of the fuse with a fuseable link on there...however id really like to use a cold wire to turn on the fan if i can. i need help.

mike

 

Not familiar with TBI cars, but I'll give it a shot. If I remember correctly, there is a fan relay up near the side of the radiator on the passenger side. I may be mistaken, but I didn't think that any of the three on the driver's side firewall were fan relays.

 

well the only other relay i saw was right next to the blower motor. and id only assume thats for the blower motor, ya know?


im really stumped, im usually pretty good at this stuff

 

Yeah, that one is for the blower motor. The one I was talking about is about 3 feet forward of that one. Look just ahead of the battery or charcoal canister (whichever is on the pass. side in your car). Actually, I don't even remember if this is the correct relay. We'll have to check around and make sure...

 

I'm in the process of wiring my own fan switch for my car which is a 91 305 TBI, same as yours except the year. It was my understanding that the computer controlled the fan but from some research and hands on investigation that doesn't seem to be true. The ground wire is always grounded and the hot wire is controlled by the fan switch. If your fan goes on at like 220 than you have a fan switch. If not then its located somewhere else or something.

It seems kinda weird that it wouldn't be there. It normally on the passenger side looking from under the car up right before the last exhaust port. When I took mine out coolant leaked out.

The only way I can see the fan running with the switch now is if I run the hot wire through the car, which I didn't want to do.

One end of the wire connects to the battery the other end splices into the hot fan wire with a 20amp inline fuse right after the battery end. The switch goes in the middle where ever. This allows the stock setup to still work the way it was designed. I'm probably gonna do that setup tomarrow if nothing else comes up.

 

Disconnecting AC wires is supposed to make the fans come on?
I know someone is going to jump in and tell me that i'm an idiot for doing this and I probably am, but I made a fan switch buy just getting a switch at radio shack.
I followed the wires comming from the fan, and came to this sensor for the AC, and when you cross the 2 wires the fan comes on. So I just spliced into both of them, ran them to a switch from radio shack, and when its turned on the wires are crossed and the fan turns on. It hasn't killed anything yet.

 

pyro,

You used the same part of the circuit as was mentioned regarding the A/C pressure switch. If I remember correctly, the way this works changed at some point in thirdgen production. Some years (my car for instance), unplugging the connector from the switch (creating an open in the circuit) causes the fan to run. In other years (yours), connecting the two wires causes the fan to run. If you had just pulled the connector and used a jumper wire to connect the two connector terminals, the fan would run whenever the key is on.

Most people seem to use the relays for their switches, but I don't see any reason why it couldn't be done in the A/C pressure switch circuit.

 

I'm new to this board but i thought i might spin a tale for you. I have an 86 TPI Z28, the electric fan is controlled by the computer. I started with a 3 row copper radiator, had the radiator fan relay hot wired to run any time the ignition was on, and put a 160 degree Thermostat in. It would still get hot during the summer, and eventually, since the ECM controlled the fan, the constant current flow killed the Quaddriver in the ECM. So after i fixed the ECM, i bought a new connector from the dealer, and new relay, and got the fan working like it was originally intended. The ECM on my car wont turn the fan on until 240 degrees, which in texas is death for that engine. I installed an aluminum Modine radiator, and it worked a little better. I then read a post, i think it was here, or somewhere on the web about an adjustable thermostat to to turn off and on the fan. I called Oreillys and they had something very similiar, an adjustable fan relay that you can wire up and adjust to make it come on from about 100 degrees up, and i wired it so that the GM relay came on incase the Hayes relay crapped out. It has a probe you run through the radiator that workes really good. This system runs really well, it cools it down much better now. Make sure you have an air dam underneath the car thats in good shape, if its curved significantly or missing, it needs replacing. I noticed that those thermostat crap out eventually after 12 months of heat down here, so when everything else is ok, i change out the T-stat. Those electric fans these cars came out with really dont blow enough CFM for over 200 horses, im planning on getting an aftermarket one that blows more CFM and uses less amperage. Check your timing too, too much timing will make your car run hot. My fathers IROC has that stupid sensor down there at the bottom of the block, we put that Hayes relay in there too, and that thing cools. When you put the A/C on the fan is supposed to come on. Have fun with your cars.