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lepetitprince

Fan problem: need help understanding what is wrong

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Hi all. I have 82 Brat, I guess its special year and manufacture did some funky things to it. I have two fans, one of the connects to thermoswitch, and the other was connected to thermoswitch but never got it to work. Even with all those tactics we know for 82 Brat. With headlight off, a/c on or off, all those things, I never got it to work. So I decided to hard wire it. With little switch the fan works even the engine is not on. So assuming both of the fan will work, one day when engine was hot, I checked under the hood, guess what, only hardwired one was working. Found out later that wire wasn't connect to the thermoswitch. Soon after I connected back the wire into the thermoswitch, hardwired fan stopped working. So I pulled out the wire from the thermoswitch. played with hardwired fan, and got it to work again(caused my half of my fingernail from my ring finger); pull out the fan wire from the thermoswitch and played with switch on the hardwired fan, and when it was working, I plugged back in the fan wire into the thermoswitch. Today I installed new thermoswitch, plugged in the fan wire, and now guess what, my hardwired fan doesn't work. What I dont understand is that, my hardwired fan has its own relay, so I don't think there ins't any limitation of when should the fan work or not, but everytime, a wire from the other fan is connected to the thermoswitch, the hardwired fan doesn't work, and vice verse, when hard wired fan is working, the other fan that is connected to thermoswitch doesnt work even at its specific engine temperature. I would like to understand why this is happening. And thank you in advance, and sorry for confusing questions and explanation.

Thanks

Dan

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I suspect that you have the wrong kind of relay. From your description, it would appear that the relay is the "normally closed" kind. This means that the contacts are closed until the coil is energized, at which time the contacts open.

 

You need a relay in which the contacts are open until the coil is energized. If you've bought a relay from an electronics store, you may simply have used the wrong pair of contacts -- most electronics relays are double-throw.

 

Why don't you just wire the two fans in parallel, and forget the second relay? I think you'll find that the first fan is already being run through a relay, and that the relay should be able to take the load of the second fan. If your fan fuse blows when things are wired this way, you'll need to add the second relay with its own supply and fuse. Don't install a bigger fuse.

 

When you use a second relay, run the two coil wires to the first fan so that the relay will turn on and off at the same time as the first fan. Don't try to control the relay directly from the thermoswitch.

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Dan, simplisticly I think you have a bad ground somewhere that is creating your fans' "odd" behavior. However, if you research the Board a bit, I think you'll find a suggested wiring diagram for getting both fans to work. Sometimes it's easier to just re-do something than to try and figure out what's wrong.

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