Bad Fan Switch?

[duval7]

So I followed the fan wiring thread in this section, thats a very helpful thread BTW. I have a Mishimoto radiator, spal fan, E30 coolant bottle, and the 82*C switch. I also have the brown top coolant sensor so my gauge reads correctly and an aftermarket coolant gauge for a more precise reading. I have never been able to get my fan to come on except when i short the two prongs on the switch. As soon as i shove a screwdrive in there it turns on but thats the only time. Today i let it run up to 200F with the OEM gauge just tipping over the half way mark and still nothing. So i unscrewed the switch with it running to let a little coolant out, thinking maybe there is trapped air at the top of the end tank and still nothing. I Ohm'd the switched right after i cut the ignition off and its at 4 meg ohms. So i just have a bad switch right? Really at 180F I should have little to no resistance at the prongs? Is that what you guys think?

[Tico Frank]

Same problem here except I am running an m42 radiator.

[NickL]

Its very common to get bad fan switches. Some have had good luck some have had terrible. I got a good one first try on my swap car.

But on my E36 the on I got was junk. Try ordering from pelican, thats where my good one came from. And make sure all the air is out of the system as well.

[frankie591]

does the fan come on if you hit the ac button?

[duval7]

Mine came from pelican, guess i will try again.

I didnt wire it to come on with ac just to come on when the temp is reached.

[frankie591]

did you use the stock aux fan wiring? If so it should come on when the ac is on.

[duval7]

I honestly dont know. I wired it exactly like the write up instructed, I am just not sure if its supposed to come on with the AC. I will give it a try and see what happens. It comes on as soon as i jump the switch tho.

[reelizmpro]

Its very common to get bad fan switches. Some have had good luck some have had terrible. I got a good one first try on my swap car.

But on my E36 the on I got was junk. Try ordering from pelican, thats where my good one came from. And make sure all the air is out of the system as well.

Happened to me before as well. It's also common for the connector terminals to corrode.

[Bimmian89]

heat up the sensor with a torch if it doesnt come on even still id get a new switch or sensor.

[328ijunkie]

^This. A lighter works a little better so you dont melt everything but same principal. Connect the switch as normal and try manually heating it up with the key in on pos. It obviously should fire the fan after a little of heating it up. If it doesnt then the switch is dead. Ive *knock on wood* not had a bad fan switch come through here yet. Typically air in the system, a slow/to high of a thermostat, or a slow/off factory temp gauge can cause it to turn on (or seem to turn on) late/not at all.
I have some cars that seemingly dont turn the fan on till the 3/4 mark but the cluster is also off compared to live readings.

[duval7]

^This. A lighter works a little better so you dont melt everything but same principal. Connect the switch as normal and try manually heating it up with the key in on pos. It obviously should fire the fan after a little of heating it up. If it doesnt then the switch is dead. Ive *knock on wood* not had a bad fan switch come through here yet. Typically air in the system, a slow/to high of a thermostat, or a slow/off factory temp gauge can cause it to turn on (or seem to turn on) late/not at all.
I have some cars that seemingly dont turn the fan on till the 3/4 mark but the cluster is also off compared to live readings.

OK so here is what i found out. I pulled the switch out of the radiator and held a lighter to it with an ohm meter hooked up to the prongs. It took almost a full minute of the flame setting on it before the switch finaly clicked. So I dont think the switch is functioning right. It had to be way over 82C setting in the flame for that long. I ordered a new one from Pelican this afternoon.

I dont have AC in my car and when i hit the snowflake button the button itself doesnt light up but when i hit the recirc button that botton does light up but the fan doesnt come on with either button pushed. So i dont know if the wiring for the AC button is not functional or the snowflake button doesnt light because the AC system is incomplete.

[duval7]

My new fan switch arrived today. I tested both my old and new switches by setting them directly in a flame and it takes a full minute for both switches to close. It seems odd that they take that long close while in a flame and they should close at 180F. I guess today i will install one in my radiator and run the car and see at what point the fan comes on. What is a safe temp to run the car up to? I dont want to warp a head or blow a headgasket. The first time i ran the car for an extended period it got up to 200F which is a little over the half way mark on oem gauge before i cut it off as the fan never came on, maybe i should give it more time.

[duval7]

I installed the new switch today and after reading several threads that stated the normal operating temp of an E36 is around 200-210F I decided to just let it run until it went over 220F to see if the fan came on. It took about 15 minutes to warm up but i noticed the thermostate didnt open until 200F, which i guess is ok considering it has a little lag time after it reaches its opening temp of 190F. The fan finally came on at 217F which is about an 1/8'' over the middle of the oem gauge. What do you guys think about that? The fan switch should trigger the fan at 180F which is 37 degrees off. fI am thinking about trying to find and even lower temp fan switch. I really dont feel comfortable with my engine and headgasket seeing that kind of pressure every day.