AC fan switch issue - No 0 and 1 speed

[kayw]

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

Kay

[944 Ecology]

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

[Jfrahm]

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.

[kayw]

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 ??

[Jfrahm]

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.

[kayw]

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?

[Jfrahm]

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.