I have my fan switch grounded with a toggle switch: green wire/with white stripe, so I can turn on the fan when I want to. I had the toggle switch off, and the fan wouldn't automatically come on like it should. Would this be a bad fan switch, or a bad relay? 92 RS 5.0 TBI

 

might be a bad fan motor. time to beak out the ol test light to see where you are and arent getting power. the orange wire is usually power, atlest it is on my 89.

 

The fan motor comes on with the toggle switch, but not when the ground switch is off.

 

Get rid of the toggle switch. When it's off the circuit is broken so the fan switch wont work as it's supposed to.

 

Get rid of the toggle switch OOh My! Anyway, grounding the fan switch is a popular method of manually overriding the fan so the engine temp doesn't reach 225. If the switch is off (not grounded), the fan will come on with the fan switch when it's working anyway. If I didn't have the ground switch hooked up, I would have overheated.

I did find out that the fan switch is not working right. If it was a relay, the fan wouldn't have come on at all.

 

IIRC, the switch on TBI engines does not close at 225 but at much higher temperatures. The number 238 rings a bell (but I might be off a few degrees). Yes, it is pretty high and it looks almost like the engine will boil out but it's just an overheat switch and as long as it works, the engine will never see 240.
So to test out the switch, just let the engine idle until you see 245 (yes, it's hot but not dangerous). If the fan doesn't kick in before reaching 245, it's time for a new switch.
Btw, make sure you are reading the actual engine temperature. The dash gauge and sensor are not very accurate to begin with so I recommend to use an external thermometer (non-contact IR type or similar) to see what the actual engine temperature is.

Hope this helps.
Lou

 

I know the gauges are not accurate, but my gauge read higher than before, and the fan didn't kick on. I didn't wanna push the envelope, so I cooled it down with the override switch. I am gonna replace the switch soon. About 11.00 at autozone.

 

If I understand correctly, you want the fan to be able to turn on automatically when the engine hits a certain temp (via the ground switch).

And you want to be able to manually control the fan on/off with a toggle.

SO basically you want to control the fan switch with a toggle and still have the temperature ground switch turn the fan on if you start getting too hot?????

Easy to fix. If I understand how you have it wired. It sounds like you have both switches in series.

Now install your toggle switch with a grounded wire in parallel to the temperature switch. That way when you hit the toggle, the relay gets ground and the fan turns on. Also if the toggle is off, the temperature rises, the temperature switch closes, the relay gets ground, the fan turns on.

 

I believe you are describing the way I have it wired. When the weather is cool, and I am cruising 35-40 or faster, the fan need not be on to keep the coolant temp at 180*. When it is hot and in standstill or slow traffic, I want to be able to keep things cooler than 225* which is too hot for me. I believe too much heat will rob performance and engine life.

 

Im lost.

Does it work how you want it too?

Can you draw how you have it wired?

 

The original thread started with "do I have a bad fan switch or bad relay" . Since then I have figured out it's my fan switch that is bad.

I can manually override the fan switch by grounding the green w/white stripe wire that connects to the fan switch to the fan relay. I can turn on the electric fan with a toggle switch I have under the dash.

 

Ah, I think I finally know what you are talking about. Or atleast Im glad you know.

So it is all working properly now?

 

I'm replacing the fan switch today. Then everything will be alright.

 

Get ready to drink some coolant if you're doing it from under the car.
Though, it's not as bad as replacing the knock sensor, that hole has more static pressure on it and is a bi*ch to thread back in.

I am curious what temperature the new switch will close at. The stock replacement should still be at 235+ F.

Lou

 

Well Lou, I have drank worse stuff. Are you saying the temp sensor is difficult to thread in, or the knock sensor is difficult?