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Re: ACC fan Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Mon, 13 Jun 2005 07:02:13
In Reply to: ACC fan, Roverboy, Mon, 13 Jun 2005 06:10:49 Members do not see ads below this line. - Help Keep This Site Online - Signup |
The ACC has a built-in fan controller that uses a transistor to vary the voltage, and therefore the fan speed. A common failure mode of the transistor is to short, and the result is the motor running at full speed.
In non-ACC cars, there is a manual speed control switch. I don't know how they could have installed that in a ACC-equipped car, but I guess it is possible. The maual speed control switch uses a series of resistors to create voltage drops, and therefore control fan speed. The stock resistor pack plugs into the side of the fan case, just under the aquarium cover. The resistor pack has a thermal fuse to protect the resistors in case of a motor overload. If that fuse blows, the fan will only work on high speed.
My guess would be that when the original ACC transistor controller failed, the PO retrofitted a manual control. A lot of work, given that the transistor can easily be replaced, and the fan controller is easy to replace. Maybe he had a donor car lying around. Given that the car has been modified, it's tough to say what is wrong and how to fix it.
If you have an ACC-equipped car (automatic climate control), I would look into fixing the fan controller, and get rid of the manual speed control. See Quasi's page (http://www.quasimotors.com/transistor.htm) on fixing the tansistor.
If you want to stick with the manual control, pop the cover off the aquarium, and look for an electrical connector on the driver's side (US cars) of the blower motor cover. Pop it out, and there will probably be a resistor pack in there. The thing that looks like a diode is actually a thermal fuse. You can replace it (the fuses can be mail-ordered from electronics houses), or simply bridge it with a wire.
If there is no resistor pack there, then the PO put it somewhere else. Now, all bets are off. How it was wired, only Loki knows.
posted by 192.249....
, Mon, 13 Jun 2005 07:02:13 <-- Viewing This Message, Mon, 13 Jun 2005 12:10:00
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