Engine cooling fan

[Mike McKown]

I don't want to go into the whole story but I have a Festiva with the engine cooling fan disconnected. It has the wrong thermostat housing on it so no sensor switch to turn the fan on.

The coolant sensor wire is just dangling, the fan motor lead disappears out the bottom of the car into a wire harness. I guess it is wrapped up in one of the harnesses.

What I want to do is put a toggle switch on the dash to turn it on manually when needed. If that works out, I could go with a automatic deal where it senses coolant temperature and turns the fan on that way.

What would be the best way to wire that fan motor manually and not interfere with the PCM?

The wiring is a mess on this car and I don't want to try and put it back stock.

[nik]

Glad you asked this! Mine has a similar problem. It's not a wiring mess, just has some issue... the fan works, but for some reason it doesn't turn itself on automatically so we put a direct line into the dash and on a togle switch. Worked good... until it got really hot, then it started smoking at the togle switch. Changed the wires today. We'll see what happens. Think we maybe used to light of wire.. (small speaker wire was what was available) anyway, directly ran a heavier wire, toggle switch was bad, so for now we just connect the wires manually and will get a new switch next time we are in town. I'm anxous to hear what others have to say!

[Mike McKown]

It'd probably be best to run the juice to the fan motor through a relay to take the load off the toggle switch. The wire should be fused also.

Did you just cut into the fan motor harness? Did the manual fan affect anything else?

[ejp2fast]

when the green wire is disconnected from the cooling fan switch inside the thermostat housing, i know that the fan will run constantly as long as the ignition is one. i need a new cooling fan switch, so currently my fan runs constant as i just have it disconnected.

[FB71]

big question; EFI or carbed? They work differently.

[Mike McKown]

It's a '91 EFI.

Interesting that 2fast says the fan should run all the time with the key on. Since I don't have that sensor, my fan should be running? It doesn't but that would indicate no juice to the fan or bad fan motor?

[jglutz]

Jim....can the fan switch be installed in the place of the temp gauge sending unit?

[FB71]

ok, the green/yellow wire goes to the sensor. If disconnected, the fan should run continuosly. That wire feeds the ground side of a Normally Closed (N/C) relay. THe switch grounds the relay coil, which opens the circuit to the fan, turning it off. Above 207 degF, the switch opens up, turns off the relay which closes and energizes the fan. The fan is fed power on the yellow wire from the instrument panel fuse box. That fuse is hot in run only (labelled 'Fan'). Ground to the fan is provided by the yellow/red wire, thru the relay. The relay switches ground on and off to the yel/red wire from the black wire. The relay coil is provided power on the black/yellow wire (at the relay) in start or run. The relay is located behind the driver's side headlight. It should be grouped with one or two other relays, and covered with a rubber boot. With the fan plugged into the vehicle harness and the key on, short the black wire to the yellow/red wire. The fan should run. If it does not, check the yellow wire at the fan for power with the key on. If you have power, but the fan does not run when the black and yellow/red wires at the relay are shorted, do one more check. Short the yellow/red wire at the fan directly to battery ground. If the fan does not run, then the fan motor is bad. If the fan runs simply by shorting the black and yel/red wires at the relay, then the relay is bad.

Joe, to answer your question; if the sensors are physically the same size and thread, then they can be interchanged. Get a pipe 'T' and a short nipple, and install both the sensor and sending unit into the 'T', and thread the 'T' into the single port on the engine.