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Posted by: Phoenix-MN Sep 3 2006, 03:18 PM

I'm installing the heater / ventalation controls and don't quite understand how the electrical portion functions. From the way the wiring is hooked up it seems to me that when the fan switch makes contact for the low/medium/high settings it will also short the +12 volts to ground through the fan control arm to the ground wire. What am I missing here? Just doesn't make sense to me.
Thanks
Paul

Posted by: SirAndy Sep 3 2006, 04:09 PM

if i recall correct, the lever is insulated (sp?) by some thin paper (?) gaskets. the lever simply routes the 12V to one of the 3 prongs when moved.

the ground is for the lightbulbs that go into the left/right sockets ...

at least that's how i remember it, has been a while since i fiddled with one of those ...

easy to test with a voltmeter,
Andy

Posted by: Phoenix-MN Sep 3 2006, 05:56 PM

Well when I measure the resistance with an ohm meter I get a dead short.. There doesn't seem to be any isolation anywhere on the arms. When the arm is rotated to an ON position the 12 volts gets shorted to to ground either through the ground wire or just by connection to the chassis. This is got me stumped....... I have several controls and they are all the same.

Paul

Posted by: SirAndy Sep 3 2006, 06:05 PM

ah, wait, there's no "12V" wire on there, correct? i mean, it get's 12V through each of the 3 prongs ...

which means, the 3 wires from the fan carry the 12V and the heater lever provides ground, thus switching the fan on/off ...

as i said, i haven't had one in my hands in a while, but i rebuild two of them about 3 years ago ...

makes perfect sense, the lever switches the ground for the fan ...
Andy

Posted by: Phoenix-MN Sep 3 2006, 07:04 PM

Yup Andy, you are correct sir After squinting my 49 year old eyes at the wiring diagrams some more I saw that the motor gets 12v from the #9 fuse and the switch is grounding one of the 3 windings for the various speeds. The terminal on the bottom supplies the switched ground for the light. So....... the switch is suppose to be ground. Got myself all wound up by thinking it was switching the 12v. Re-installing the whole wiring harness is getting to be a real adventure.

Thank you for your replies

Paul