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Old 04-08-2005, 09:07 AM
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Adjustable Fan Thermostat Working in Reverse

I installed an adjustable thermostat in the ground side of my electric fan circuit. It seemed to work fine before the car went to the AC shop. I could set the knob about mid- range and the fan would cut on or off as necessary at about 195 degrees (with 180 degree thermostat).

The AC shop said they were going to wire the fans into the AC circuit so that they would also come on anytime the AC was activated.

Since getting car back from the AC shop, the fans now immediately come on when the car is started cold. As the car warms up the fans go off and I have to keep dialing up the adjustable knob further and further to get the fans to come on when the car starts getting hot. If the car gets too hot, the fans aren't activated by the thermostat no matter how high I turn it.

The problem only really became clear when I drove the car to the upholstery shop the other day. It got hot in traffic and I had to pull into a parking lot to let it cool down. After it cooled a little, the fans came on and then stayed on as the car cooled down and I went on my way.

Of course I will take it back to the AC shop when I can, but does this sound like a wiring problem or a bad adjustable thermostat.


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Old 04-08-2005, 09:55 AM's Avatar Moderator
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Do the fans go off when you turn on the A/C? Sounds like a relay hooked up normally closed when it should be normally open. Do you know the details of the circuit they installed? Did they add a relay?
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Old 04-08-2005, 11:43 AM
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I think Willys has hit the nail. If you can track down the wiring to the relay the AC shop put my guess is they have one (or more) wires on the wrong prongs of the relay. If you can see how it is wired (and the color wires for each prong) you might be able to just call the AC shop, describe how it is wired, and have them tell you if something is backwards.
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