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Vigman Q: fan switch/relay question



OK...a month ago the thing worked fine. All of the sudden, my temp goes sky high (230 +). I take it straight home, shut it down and find out that my relay is crispy. I go to GM and get a new relay and pigtail, install same and now instead of the fan not turning on, it won't turn off. I think it is the fan switch (it is supposed to turn on around 170 and off around 160), so I get a new one from hypertech. I just installed it and have the same problem...goes on at 170 and doesn't go off (gets down to 158). The car cools and it seems to reset the system...fan off till 170.

Could the relay have something to do with this?
Is this something to worry about or just let is go?
Help me Obi Wan...you are my only hope;help


By The Way

Does anyone know the correct part number for the fan relay on an 84?


fan switch/relay question

Don't know when this was posted but I see no responses yet.
It depends on how you installed the switch. If you installed it the way Eckler's switch is installed then the switch is pretty much in control of both fans. Assuming you have two fans. If not it is in control of the main one anyway. If not, the fan controls one and the ECM controls the other. They are stort of independent. I have mine both controlled by the switch. The way the fans are installed is with one side to ground and the other switched 12V. The relay of course, provides the12V. So if the fan is staying on continually the relay must be pulled in continually. That's probably why it got fried in the first place. If you look on the 3rd pin from the left, facing the relay, it should have 12V on it all the time. You will also see the same 12V on the 2nd pin from the left if the relay is not pulled in. (engaged) The way it engages is by the switch or ECM applying ground to that 2nd pin. When it is engaged you won't see any voltage on it. If that is the case you have a bad switch. It should only be engaged when it hits the high temp. There could also be a short to ground somewhere between the switch and the relay. If you did like me and changed the wiring, did you cut off the old wire or leave it dangling? That could cause a short and leave the fan on all the time, especially if you removed the connector and left a bare wire hanging there. :)

You used "fan" in the singular so I assume you have one fan. Then that is the only relay you need to deal with. If you had two fans you would have two relays, etc.

If you short pins A and B on ALDL and turn on the ignition the fan(s) should come on. If you turn off the ignition the fan should go off. If you remove the short the fan should go off. This is a way to check the relay alone. To check the switch pull the connector off of the switch to see if it changes anything. The fan should be off. Short that second pin from the left on the relay and the fan should come on. Be careful not to touch the 3rd pin or you will blow that 3 amp fuse for the 12V. That can turn into a red herring very easily.

Well hope this helps. Let me know if you have any further questions. It is fresh in my mind after overhauling this system last weekend.........

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