Accessory fan coolant switch
 

Ok, I finally picked up an accessory fan harness at the junk yard yesterday and I wired up my SPAL fan to the factory harness. Now my question is at what temp is the switch supposed to turn the fan on??? I warmed up my car and let the coolant get up to just 220* on my Autometer gauge and the fan still hadn't turned on so I'm wondering if my switch in the radiator is bad or if I'm just missing something...

Re: Accessory fan coolant switch
 

I run my slim fan off a toggle switch inside. Simple and Easy. Run it full time durning stop and go traffic, and turn it off when doing those hwy pulls, or any freeway driving. Just keep your eyes on your gauge. BTW. 220* is pretty hot. try to keep it around 180*

Re: Accessory fan coolant switch
 

220 isn't too hot, many gm cars I know of run 210 - 220 from the factory as well as my girlfriends blazer that stays at 220 all day long. My car normally runs 185 - 190 while constantly moving but rises quickly when stopping and going frequently. I had two slim fans hooked up to a toggle inside the car, but I don't like this because on two occassions I've caught myself turning the fans on late when the car is creeping up to 225 - 230. I'll leave my smaller one toggled, but by hooking the large fan to the factory sensor would eliminate having to worry about switching fans on all the time when the car gets warm. Anyway, does anyone care to elaborate on my original question...

Re: Accessory fan coolant switch
 

210 and higher is getting pretty hot on our cars. Its not very good for the engine to run so hot. Either your thermostat is not opening all the way or something else is wrong (rating)? My car without a fmic sat at about 196 all year round, but I put the FMIC and cruising around with 1 stock fan it went up to about 206 to 210 without AC running.

I would use some water/waterwetter mix and lower the temps a bit. Your oil must be uber hot at 230 water temps.

Re: Accessory fan coolant switch
 

on cast iron heads

220* on a aluminum head is just asking for a warping. NOT saying it will, but its not good. Ive gone up to 240 before and I thought it was all over for my poor ported head, thank god it wasnt.

Re: Accessory fan coolant switch
 

Ok you've got a point there, I wasn't thinking alum vs cast. But my car does stay relatively cool at 185 - 190 as I stated before. I'm not trying to solve an overheating problem, just simply trying to figure out when the temp sensor is supposed to turn on so I know if mine is bad or not. I'd like the fan to turn on automatically instead of me forgetting about it one too many times and f***ing up my car.

Re: Accessory fan coolant switch
 

I believe the coolant switch is the sensor on top of the housing, above the thermostat, facing the exhaust manny. check the wires coming out of it, there usually fried from being so close to the exhaust manny.

Re: Accessory fan coolant switch
 

EDIT: didnt read close enough. Im not sure when there supposed to turn on. I think they turn on after the t-stat opens up, and turns the cooling system into a completed loop. OEM stats open up at 180?? maybe.

Re: Accessory fan coolant switch
 

Man, I turn mine on every time I get in the car, before I even start it up. the toggle also has a red led in the tip, so I don't forget to turn it off. I even have my fuel pump off of a covere-d toggle, for added security..only blows when I gotta leave it on for the auto-start..

-A. Swift

Re: Accessory fan coolant switch
 

The fan switch is on the lower corner of the radiator itself, it should turn the fan on at 185 F

Re: Accessory fan coolant switch
 

You can test the sensor with some boiling water and a multimeter.It should read around 0 ohms at ~185 F and higher.You can test the rest of the circuit by shorting together the 2 wires going to the sensor.When shorted together, the fan should turn on

Re: Accessory fan coolant switch
 

Thanks for the info Eric. I've tried looking everywhere. I'm assuming if 185 is 0 ohms then there must be some resistance when at room temp (figure I should maybe check this also...)? I was just thinking I could warm the car up to 185 and take a reading instead of taking the sensor out first. If it checks out ok, then I'll jumper the terminals at the plug to see if the fan turns on as you stated. I'll post up what I find out.

Re: Accessory fan coolant switch
 

It should be an open circuit below 185F.

Re: Accessory fan coolant switch
 

By 0 ohms, I mean its essentially a closed switch, in reality it may be above 0(and be fine), but the resistance should be low.

Re: Accessory fan coolant switch
 

Gotcha. Well, I can't find my damn multimeter right now so I tested the fan circuit by shorting the two wires and the fan turns on, so I'm 99% sure that the switch/sensor is bad without even testing it unless there's something else I'm missing.

Re: Accessory fan coolant switch
 

Unless there's something preventing the sensor from reading coolant temp(coolant not circulating, etc), the switch is your problem

Re: Accessory fan coolant switch
 

Thanks again Eric, if a new switch doesn't work for some reason, you might be hearing from me again.

Re: Accessory fan coolant switch
 

For future reference.