I've notice my metal fan switch is getting very hot to the touch when the system is on (heat or AC running; I don't think it is doing this when the system is just on the vent setting). Any ideas on what is causing this?


Thanks.

I should clarify...extremely hot at times. Almost like you could burn your finger if you held onto it.

The contacts inside of the switch are probably varnished with age. To clarify, it is really corrosion... The older an electrical contact is, the more likely you'll have an issue like this.

When an item is new, you have very clean contacts inside of the switch, once it gets older, and from a lack of use, the connection doesn't make full contacts anymore. This builds up heat.

Unless they make the contact out of gold (like NASA does) corrosion will rear its ugly head on older make/break contacts like this.

Now, you could also have a downline resistance buildup in the motor, the resistor pack or even a rubbing electrical line or a loose connector inside of a quick disconnect electrical connection.

Remove the electrical connections and clean each contact with light emery or a very small wire brush. Depending on the material of the connector, you would clean the male and female ends so that it looks like new copper or silver.

Ask Sky Sam about his electrical connectors being very hot to the touch on his motorhome. I looked at his coach in Washington DC and his light switch was too hot to touch.

After spending a few minutes cleaning his contacts, it was much cooler.

Radio Shack also carries a contact cleaner that may be helpful.

I had a problem with my Kawasaki KZ1000 police bike. The main 30A fuse would blow. Someone suggested DeoxIT on the clips that hold the glass fuses. The clips would weaken over time and become tarnished. A pinch with the needlenose pliers and some DeoxIT solved the problem until I replaced the fuse box with an ATC unit. The poor contact created heat and the situation only got worse as the wiring heated up. The fuse element actually desoldered from the endcaps so the fuse looked good. This is a well documented issue with KZPs.

Anyway, I already used Deoxit on my blower switch when I installed the new radio in my Barth. There was a ton of Arizona desert in the dash to clean out. The blower switch moves real smooth now.

Thanks very much. That all makes sense, and I'll see how to get to the switch and check out the contacts. Hopefully, that will do it. If not, you've given me some other things to look into Bill. Thanks again.

Hadn't heard of Deoxit before, but just looked into it. I see on Amazon that nearly everyone raves about this product. My switch seems to move smoothly enough, and my coach hasn't spent much time in the desert so far as I know! But will clean it all out and probably will try the Deoxit. With nearly 20 years of age on all of the electrical contacts everywhere, it sounds like I could find it very useful. Thanks.

Vince my switch gets warm to hot depending on the setting I have it on, I have not cleaned it recently and it probably will help, sometimes overheated motor switches are a sign of a motor degrading and drawing higher amperage.

I will check mine this week and report back

Thanks Ed. I did remove the unit and the switch this morning. The switch is sealed, and I can't see much of the insides. But I've sprayed contact cleaner into it, and it doesn't appear to be corroded. The other contacts look good, so I'm thinking the problem may be downstream as Bill and you have mentioned. Will try to locate the motor next, and follow the wiring to it. Mine has been getting VERY hot...sometimes enough to burn your finger, as Bill mentioned. I can see signs of the heat where the switch mounts, in the form of some deformed plastic which must be due to this. Also looks like someone was in here before working on this. Guessing they weren't too successful...or their efforts didn't last long!

That fan switch has been usednby GM and Chrysler since the 1950's and was always failing. Just like the headlight switch they run full amps through a small switch rather than spend a few more bucks to use a relay. In addition to getting hot it is consuming several volts lowering the power to the fan. Just as we are changing the headlights to relays the best solution is to add a relay under the dash and then use a mineature switch. Both the
fan and your hands will be better off.

The fan motor speed is regulated by wire resistors - the more resistors are employed, the greater the voltage drop across them (and the lower the current passed), and the slower the motor runs.

These resistors are simple coils of wire, and rarely fail short - always fail open. And they're pretty hardy.

I'd suspect the switch. Exercising it (lo-hi-lo repeatedly) may clean the contacts, but this is of little help if they're pitted or badly corroded.

Thanks Tom and Rusty. Finally got a chance to test my fix out, and it seems fine now. Ran the heater with the switch on high for over 40 minutes, and it barely got warm. Prior to this, it would have burned your finger! Huge difference. So it apparently was the switch. Sprayed inside the switch with the deoxit, and worked the contacts a number of times. Also cleaned/sprayed the connector, although that looked fine. Of course I found that someone had been in here before, and one of the plastic mounting ears had been broken earlier, and poorly repaired. But a little JB Weld and I was back in business. Thanks again.