Speeds on fan in the car

Discussion in 'General Electronics Chat' started by orwikcons, May 4, 2008.

  1. orwikcons

    Thread Starter Member

    May 2, 2008
    How can I slow down the fan in my car? If I put resistor (the strongest I found is 6W), it will burn, because the fan is 50-80W... Only 1 Ohm is enough, but I cannot find enough strong resistor...

    Is there other way to make this work?
  2. Wendy


    Mar 24, 2008
    Which fan? Radiator or blower? I'm guessing blower. I'd use something more electronics myself, a variable on/off device like a MOSFET connected to a slow oscillator. It'll dissipate a lot less heat among other things.
  3. mrmeval

    Distinguished Member

    Jun 30, 2006
    If it's GM and it only works on full speed the resistor is open. In essence the full speed is a dead short across the control when set for full speed. Then more and more resistors are added to reduce speed. They are a massive block somewhere around the fan. This is all potted and sealed and has a connector plugged into it. It has to be installed correctly because it might as well be another heater in the car. They burn out because the fan starts drawing higher current when it gets old so you might replace that as well.

    25 dollars to buy and 150 dollars for a contortionist to install.
  4. pfofit


    Nov 29, 2006
    Are you trying to repair a blower motor that does not work on lower speeds?
    High speed has its own fuse and the lower speeds have their own fuse.

    In the ole days, they used several coils to reduce the voltage and limit the current.

    A while back the manufacturers found out they could install a electronic resistor bank that would burn out relatively quickly(the old coils rarely burned out) and thus generate a cash cow in the parts department.

    Around 30 to 50 bucks.

    The board consists of several wide traces of metal to create resistances.

    The problem is that this board is installed inside the bottom of the air plenum next to the fan for cooling. Buy a new one and let in hang while you test it will surely burn it up in about 10 seconds, without the cooling of the air.

    Since it is at the bottom of the plenum an GM has designed a bad cowling system as well, water and moisture run off the window into the cowling and it gets down onto the squirrel cage and gets spread all over the board and it corrodes.

    Gm has redesigned this part several times, their latest attempt is to cover the board in a millimeter thick level of black coating to keep the moisture out.

    However this just makes it harder to repair.

    I've change a dozen of these and repaired as many. Some can be solder and bridged at the break(s), however, some have nichrome wire of sorts that cannot be soldered.

    cheers and good luck, You do need to be a contortionist...More GM engineering stupidity. The weakest parts are the hardest to service.
    Last edited: May 5, 2008