AC fan switch issue - No 0 and 1 speed
 

Hi,

Recently the Speed 0 and 1 of AC fan do not work. Speed 2-4 are good. I have replaced another used resistor but not solve.

I doubt the switch inside climate control unit but don't how to disassemble. Could I use a volt meter to test voltages on the plug to reisitor? Which terminals related to speed 0 and 1?

Thanks

Kayhttp://forums.pelicanparts.com/uploa...1730392027.jpg

http://forums.pelicanparts.com/uploa...1730400303.jpg



This snippet of the wiring diagram should help you figure it out.

You can clean the little bimetal thermal switches on the fan resistor module in the blower motor assembly. Hold them open with a toothpick and drip some vinegar on them.

It can also be the switch on the climate control head, they do fall apart.

Thanks for advice. If I test the plug (shown in the photo of first post) with voltmeter, connecting ground and each termials one by one? 5 termials correspond to speed 0-4 ??

Testing with a DMM might not be definitive, you might see continuity under no load and with any significant load it could go away. I would test with a test lamp, maybe a headlight bulb and not a little pen-type test lamp. This is to simulate the blower load which is on a 30 amp fuse (a lot more than a headlight bulb).

If a DMM is all you have you can try it, if the circuits are dead they are dead. At the resistor block connector end it looks like socket 5 is ground and 1-4 should get power with the fan switch in the relevant position, but numbered the opposite way. Socket 1 = fan high, Socket 4 = Fan lowest.

Check each to chassis ground and also to the ground socket. If it looks OK I would test again with a headlight bulb but make the test lamp connection and then flip the switch to avoid a small arc.

Sounds like a pain but a circuit failing under load is exactly what I see with switches like the blower switch, they might test good with no load and fail with a good load.
I have also seen the switch crack apart inside the control head.

I drop the resistor into vinegar to remove rust. It works.

I figure out how the resistors working with speed 0-3. All resistors are good, but the little copper contactor in one of two switch is open. It causes no current in sp 0 and 1.

I bend the copper piece but insuccess. Could I drop a glue to hold them together? It raises a question : what is the purpose of these 2 switches?? "110℃" marked on the switch.. does it relate to temperature?

http://forums.pelicanparts.com/uploa...1730647113.jpg
http://forums.pelicanparts.com/uploa...1730647113.jpg

Yes they break the circuit if they get too hot. I usually hold the contacts open with a toothpick and use vinegar to clean in between the contacts. It is hard to clean them when the contacts re touching.