Another Electric fan thread

[madman23]

Before I start yes I know there are DIY's but none of them answer the question I have.

I purchased a Spal thin mount 16" fan and went to mount it with the Spal wiring harness. With all of the threads I have read it seams most E30s have 2 wires going to the temperature gauge attached to the radiator. I have 3 wires going to it. The only wire that gets power no matter how hot the engine is the green wire. I do not want to wire this to a switch because to me i like the piece of mind knowing it is just going to turn on and I do not have to constantly look at the temperature.

[nando]

Only early cars have a 2 wire switch. All ix's will have the 3 wire version.

one wire is a low temp/low speed setting. It's supposed to go through the resistor bank which reduces the speed on the stock fan (and also the load). The other wire is a high speed/high temp setting. The 3rd wire is just a ground.

The stock E30 fan switch is something like 90/99c. That's too high to be effective. the E36 M42 fan switch I think is 80/88c or something like that, and works much better.

I think I wired mine up to the 88c wire for full power. The low speed circuit isn't made for the same power draw as the high speed, I wouldn't recommend running it off the low speed without the resistor bank wired in.

If the high speed never comes on, either the relay/fuse for it is dead, or the switch hasn't reached 99c yet.

[madman23]

Awesome man. Thanks for the help. Does anyone know which wire is which? I am going to try a new relay both high and low speed. I will also order a fan switch from the E36. Thanks again. Ill let you know the result.

[nando]

if you look in the ETM you should be able to tell by the color.

also I noticed a typo in my original post. with stock wiring, the high speed would come on at 88c, and the low speed at 80c. I wired mine so the high speed would come on at 80c (also left the 88c connected so it wouldn't shut off if for some reason it reached that threshold while the fan was still on). Basically I bypassed the lowspeed circuit entirely.

[madman23]

I got a new sensor, fuses are good, and tried new relays and still nothing.guess ill just be wiring it to a switch.

[nando]

there's a section in the ETM dedicated to diagnosing the electric fan circuit. There might be a diode or something that you need to repair.

having a switch IMO, is not the best solution. Yeah, you can turn it on/off when you want, but it's better to be controlled by engine temperature than having to remember to turn it on all the time.