Hey folks, I landed my dream car 8 months ago. 91 firebird convertible and have done a fair amount of work to it. The hvac heater switch literally glows orange and melted between pins 4 and 5 , but everything works. Also noticed a melted connector under the hood that controls the cooling fan and blower. I did replace it carefully.. I can’t for the life of me find that 5 pin rotary switch or even a part number anywhere. Anyone have an issue like this? And for the love of god, anyone know where to get one??

 

https://www.classicindustries.com/product/sw296.html
this *might* be your switch. I'm sure another member on these boards has a used one somewhere.
I'd look at the whole system. While the switch may be bad, you may also have a short down the line, gets things hot and the switch was a weak link.

 

Jesus christ, its arcing. Talk about a fire hazard! Good thing you caught it. Kinda looks like you stopped the selector between two terminals causing a power surge/short, maybe. Used is probably your best best. There's still some nice ones around. No repros that i know of. I think the link above is for the blower fan speed.

 

This is common. Pin #5 carries current for the Medium High (position 3) fan speed and it is undersized for the current. Mine looked way worse than yours and I was able to recondition it and have been using it for the last 6 years. Also got a spare from a junkyard just to have on hand. Basically never use fan position 3 to avoid this again in the future.

Post #307, 309, 311, https://www.thirdgen.org/forums/ltx-...ml#post5964349

I never did find the correct switch sold new. All switches are falsely advertised, even GM. I have two new switches you can buy at a discount if you want to try them out.

https://www.thirdgen.org/forums/mid-...-sell-off.html

 

You guys are really cool cats around here for the help, I did buy one of those but when I saw pin 4 and 5 are hanged together I thought it was the wrong one. Even the gm site shows one with 4 then 5, same part number. I probably did this, in the summer I was using the max setting to keep the cooling fan on in traffic or the city. I do have two climate control heads coming, one today, one switch via eBay, the electrical connections under the dash look fine. My blower itself was toasted, bearings make a shitload of noise too. I’ll let you know if there is a shirt somewhere or if all is well after, in better news, I did find my pesky vacuum leak while I was in there! Silly diaphragm switches to be honest.

 

I am resurrecting this thread because I don't understand this statement: "Pin #5 carries current for the Medium High (position 3) fan speed". I understand that the function control switch powers the fan, but only through the fan speed switch (except for modes like max cool which require high speed). The fan in my 89 IROC heater-A/C quit a couple of years ago. I replaced the fan motor, but operation was still intermittent. So I replaced the fan speed switch with an aftermarket one. Now two years later, the fan is inoperative again on all speeds. The fan motor itself works fine when fed with 12 volts directly. Based on this thread, I am guessing that it's the function control switch that's burned out.

 

You need to put eyes on the problem, that's how it will get solved. Check the basics first, like if you're getting power to switch, thru switch, etc. Follow the data to isolate the problem and drill down on it until you find it

On my Firebird the first three fan speeds are actually powered thru the switch in the dash. In the fourth position (high speed) the switch throws a relay and the fan power comes from a large wire in the engine bay. I don't know if Camaro uses the same hardware.

 

Qwktrip-
Thank you. I had already completed some of those tests, but then had to reconnect the wiring to use the car -- and viola! -- the fan started working again. I don't think I can properly diagnose the problem while everything is working. If the fan continues to function properly, I'll wait till Spring to remove that switch for a closer test. But I'm still puzzled by your statement that the one pin of the function control switch carries the electrons for the medium high fan speed.

 

There is no external relay for the first three fan speeds. All the current for the fan motor passes through the switch and is fed by a fuse under the dash.

The fourth switch position doesn't work that way. It triggers a relay in the engine bay that powers the fan from a separate 12 AWG wire with its own fusible link to battery.

That's how it is on my 89 Firebird. Not all cars are the same. Some have three fan speeds, some have four. Some have AC, some don't. It's a different switch with possibly different wiring.

 

Yes, I have the wiring diagram and pretty much know how the system works. The heat/AC system in some other GM cars I have owned operate on the same basic principle. I have owned this car about 25 years, and as noted above, I have already had to replace both the fan motor and speed switch. But I did not understand the statement I quoted above.

 

There are two switches and I think that's what has got you confused.

(1) HVAC mode selector switch; and
(2) fan speed switch, the rotary dial

This thread is about the mode selector switch. It is the gateway that passes power to the fan speed switch.

Fuse block ---> mode selector switch ---> fan speed selector switch ---> blower resistors ---> fan motor

Both switches carry the fan motor current in Low, Med Low, and Med High speeds. That's how the conductor strap in the mode selector switch overheats. The current drops to very low levels when the fan speed selector is placed in position High because it's just supplying current to the field coil of the high-speed fan relay.

Basically never use fan position 3, it makes the most heat in that strap.

 

Thanks, but I knew that. But I now see the problem -- the photos above your post #4 were of the function control switch, and I thought you were referring to post #4 on that switch. I do appreciate the advice to avoid the use of the fan switch position #4.

 

​​​​​​Okay. You just got it wrong again.

This is an aimless conversation going nowhere for no apparent reason. Maybe just ask pointed questions about your particular problem and not worry about the older part of the thread.