Troubleshooting electric fan

I recently got an electric fan on my Mav.Im using an Escort 2 speed fan with a Volvo controller.It was working just fine until yesterday, I noticed the fan wouldn't turn on with the key on.
So I used my test light and found out that the fuse is good,the relay is good,the volvo controller is good and the fan is good.I am using a BMW 2 speed temperature sensor that controls both speeds on the fan.Im thinking it has something to do with the sensor because when I hook up my 12v test light to the low speed and high speed terminals on the plug that connect to the sensor the fan starts spinning. So Im thinking its a ground problem with the sensor ?






These yellow ones control the fan speed.Once I touch them with my test light the fan turns on.The other ends connect to a plug that leads to the sensor.


Here they connect to the sensor pigtails


Heres where I think my problem is.When I disconnect both the left and right pigtail and hook them up to my test light the fan spins.The middle pigtail is the ground and its properly grounded.So that's why I believe its my sensor

 

Check your grounds.

 

The temp sensor is supposed to ground the YEL/WHT wire for low speed (forget the temperature) and ground the YEL wire for high speed (again, I forget the temp, but higher than low obviously).

You can verify the Volvo relay operation by grounding them to test. If everything is good, including the temp sensor ground, then I would also suspect the temp sensor.

 

I switched out my Volvo relay for two extras that I have and I still had the same issue.The sensor is a 180/195.I grounded the yellow white and the low speed came on then I grounded the yellow wire and the high speed turned on.

 

Grounds are all good

 

Then at and above ~180F, you should have ground on the YEL/WHT wire. Connect your test light clamp to 12+ and probe to verify ground.

 

The fan is supposed to have power when I turn the key on engine off.
What do I do now to verify if it is the sensor?

 

True. The fan relays get 12+ when the key is turned ON. The relays are now looking for ground in order to operate. The temp sensor gives the relays ground once the appropriate temperatures have been reached. Think of the temp sensor as a switch that is giving and taking away ground, instead of 12+.

So, you can test the temp sensor the way I explained earlier.

You can bypass the temp sensor and give the relays ground yourself, which you actually did with the test light by accident.

 

Ok so is it safe to say that it is the sensor then?
I bought it off rock auto it was the cheapest one.I think I should of just spent the extra 15 bucks for the better one

 

Yep, I would bet either sensor or sensor ground. But since you said its ground is OK (both ends, correct?), then I would go with sensor.

 

yea both ends are good.Do I need to use any sealent on the thread of the sensor?

 

I would use teflon paste.

 

Alright, sensor should be here by tomorrow hopefully that takes care of it.

 

disconnect the wires to the sensor, hook your test light to 12V. warm the engine to 180 or above and probe the low side of the sensor. the light should come on at this time. let the engine go to or above 195 and probe the high side of the sensor the test light should light.
if for some reason the light doesn't light the sensor is bad..

 

So I replaced the sensor today and the fan still didn't turn on. So I disconnected the plug that goes to the sensor and I turned on the car and I let it warm up to 185. I then grounded my test light and touched the low probe and high probe on the temperature switch and it didn't light up. So I decided to connect the plug back on the sensor and it turned on. It seems like the fan will only turn on once it reaches 180 but prior to this incident the fan would turn on with the key on and now it doesn't. Any ideas?