AC/Heater User Fan Control - Melted Connector & Frozen Switch
 

Seen a few treads talking about heater only, original AC, or heater trucks converted to AC with this problem. Also, some posts that the switch and connector is roughly replaced every two years.

My truck is AC original, though not sure if the wiring was ever been replaced. The AC has been converted to to R134a but that work was all in the engine bay and I don't think that conversion had any effect on the AC/Heater User Fan Control switch.

1. My switch was a little flaky when I got it, meaning sometimes I had to move it up and down to get the fan to turn on. I just let it slip my mind to replace the switch, as it didn't really happen a lot.
2. Thursday~Sunday, I went on a long trip. 8 hours trip (4 each way) with hours driving around in East Texas during a car tour. So likely 16+ plus with the fan mostly on one notch below high.
3. One hour before getting home, after filling up, I couldn't get the fan off low speed. Also, the switch was not moving up/down very well. After a bit I did get it on the higher speed. I instructed my daughter, don't touch the fan switch!

I have ordered a new switch from GMC Paul's but I just had a though that I should check under the dash too. In other posts I have seen worse connectors but I'm am pretty sure I'd want to replace the connector too. Though some of the damage has gotten to the wire insulation - some shrink tube might be a okay solution for that, I hope. When I got home, I did turned the switch to the off position and this morning it is pretty much stuck/frozen in the off position now.

Sooo - I can't seem to find a consensus on the various threads/postings about the cause of this. Some say perhaps a bad ground or just replace your switch? I assume once I get my switch in, the fan will fire right up. I haven't any problems with the fan speeds (like the other posts about a resistor) or at least not until things got all melty. Which isn't really the connector but the switch inside.

Thanks to anyone who has had / seen this issue and has moved past it. Though I suppose you would have had to have the truck for a LOT of years and a LOT of AC useage to know the melting went away.

Re: AC/Heater User Fan Control - Melted Connector & Frozen Switch
 

I use to have a connector just like that. :D

A new connector will/should come with new crimp terminals. Just make sure you crimp them well. There's enough wire to cut the melted stuff off, strip and recrimp so I don't think heat shrink is necessary. My thinking is the switch current capacity is really to low for the application. Over time the contacts are eroded from the sudden surge of current through them when you turn on the fan. Over time this gets worse as the switch loses its current carrying capacity, the heat is conducted through the terminals where it melts the connector.I've considered having the switch control some relays to do this. Maybe someone has already done it. Another idea would be a PWM controller for fan speed instead. Modern cars do this so there might be something we could use.

Re: AC/Heater User Fan Control - Melted Connector & Frozen Switch
 

Over time the connectors oxidize and the resistance increases. More current flows, and heat is amps^2 times the resistance. You get melted connectors. Cleaning and tightening all the connections should take care of it.

Re: AC/Heater User Fan Control - Melted Connector & Frozen Switch
 

Okay, I like the way you worded that about the switch / eroded due to arcing / resistance build up over time, until the switch / connector more or less reaches critical mass until it melts down.

I bought the A/C Switch Plug from Manes Truck Parts, though the photo didn't show any terminals. But along with that, I did get the Blower Motor Relay, Compressor Switch and A/C Heater Blower Speed Resistor - just to have on hand.

Re: AC/Heater User Fan Control - Melted Connector & Frozen Switch
 

It starts with the contacts in the switch not the connector. Next time take a switch apart and look at it.

Re: AC/Heater User Fan Control - Melted Connector & Frozen Switch
 

Here's one of my old switches.

Re: AC/Heater User Fan Control - Melted Connector & Frozen Switch
 

You are correct. The switches are usually the fault.

Re: AC/Heater User Fan Control - Melted Connector & Frozen Switch
 

thanks guys for the input - at least I don't need to dive into the issue any further than the switch/connector.

hopefully the parts will arrive on time (or maybe early!). With it getting 95+ here, no thank you driving around! I am not sure how I got around when I a kid without AC... well I didn't get a car with AC until I was like 26 I think LOL.

Re: AC/Heater User Fan Control - Melted Connector & Frozen Switch
 

You can do like I did for a while and use a standard toggle switch or even a jumper until the parts come in.

Re: AC/Heater User Fan Control - Melted Connector & Frozen Switch
 

Got the new switch in from GMC Paul's, nice reproduction switch. It looks well made (I didn't open it) and the handle is very nice (not plastic). It operates rather nicely, better than it ever has for me.

My connector and other bits are coming tomorrow from Manes Truck Parts I like to spread the love around ;-)

Re: AC/Heater User Fan Control - Melted Connector & Frozen Switch
 

Got the rest of my parts in from Manes today and installed. The wire connector was easy enough, the connectors cleaned up nicely and the one I was worried about isn't a problem as it tucks into the new connector with no exposed wire. It's a odd connector with some open slots....

The A/C cut on switch and the relay, not so easily accessed. The A/C cut on switch I had to use my mirror to see the screws. This switch was giving me issues until I cleaned it up and put some dielectric grease on it a few months back. Now I shouldn't have to worry at all about it.

The Fan Relay was a bit easier to get to, well except the screw closest to the firewall - very tight and I had to use a wrench. Likely easier to get to if I took the glovebox out, though I am glad I replace it. There is a ground wire going to it, without this ground there is no high speed fan. The issue is the outer screw hole was stripped and that ground wasn't really secured to the metal of the relay. I am surprised I was getting high speed at all. I had to go with a little bigger screw to get a good bite out of the plastic to get it tight. Personally, I think this ground wire to a screw going into plastic for the relay ground is a bit crap. I almost tapped a new hole in the bracket so the ground could be screwed directly to the relay metal... I might still do this at some point.

As for the resister, I got that too but I am going to hold off installing that and just keep it in "stock". The cool thing, it came in a nice GM parts box, so it seems OEM!

Re: AC/Heater User Fan Control - Melted Connector & Frozen Switch
 

That screw needs to tighten up into metal for a ground path. From looking at the wiring dia. the black wire grounds the relay case out by the blower motor. If it is not tight you will have a lot of resistance and or an open circuit. More than likely your fan switch was worn out and the extra resistance inside the switch created a voltage draw that over heated and melted the connector. I am glad to see that you were able to save the factory terminals. They are a much stronger connection then you can make by crimping a new terminal by hand. When I have to replace a terminal and hand crimp it I ALWAYS solder that new crimp.

Re: AC/Heater User Fan Control - Melted Connector & Frozen Switch
 

Well, I revisited the relay again this morning. The back screw really wasn't fastening down good and allowed the relay to flop a bit from that back. I figured that movement would cause the front screw to loosen over time. I found a good larger screw that tighten properly. I also cleaned up the ground a bit more and all the connections got a little dab of dielectric grease.

I shouldn't need to get under there again or at least not for that relay.

Re: AC/Heater User Fan Control - Melted Connector & Frozen Switch
 

Looks like this didn't get very fixed 2 years ago - the incoming +12v line is starting to melt again around the connector :(

I am assuming the switch is getting toasty inside too, so going to replace it and the connector again. This time I'll replace the resistor pack...

I did pull the fuse and it seemed okay. I started to polish up the metal end caps of the fuse and one end was loose/moving. So I replaced it with a new one. Guess I need to check the motor ground, not sure what else to check after all that.

I guess I am going to have to keep a eye on that connector for now on.

Re: AC/Heater User Fan Control - Melted Connector & Frozen Switch
 

Not sure where the body ground is on a '72. The body ground on my '68 is under the passenger side floor pan outside the frame rail.

Re: AC/Heater User Fan Control - Melted Connector & Frozen Switch
 

Make sure you have a good ground to the motor. Clean it, polish the ends, star washers, whatever you can do to make sure it has a good ground.

Re: AC/Heater User Fan Control - Melted Connector & Frozen Switch
 

I am pretty sure I didn't touch the motor two years ago. From your "check list" I assume the case of the motor is the ground [to the firewall]? Better pick up some star washers, that seems like a good idea.

I should be able to do that this weekend and get my "in stock" resister pack in. Knowing my luck doing both of those will be a PITA ha!

Re: AC/Heater User Fan Control - Melted Connector & Frozen Switch
 

I don't think you need to look any places in the wiring and grounds for the melting connector problem. The problem is at the melting connector. Resistance there causes heat. When you replaced the connector before, did you only replace the plastic connector and insert the old terminals with old wires into the new plastic connector? If so, I think it is time to replace the connector with terminals/pigtail wires and use soldered connections and heat shrink tubing to connect to the wires of the cut off old terminals/connector. Add solder to the crimped terminal to wire connections and make sure you see the solder wicking into the wires and look for a shiny solder connections. Use 60/40 rosin core solder, that good known to the state of California as being extra dangerous stuff.

Other than right there at the hot connector, the other thing to check is voltage at the battery with engine running higher than idle. If higher than 14.5 volts you may have an overvoltage problem.

Re: AC/Heater User Fan Control - Melted Connector & Frozen Switch
 

I think many misunderstand the purpose of dielectric grease. It prevents the flow of electricity. Commonly used on pipes and connections to prevent electrolysis. My understanding is it goes over the connection not in it if you want a good connection.

Re: AC/Heater User Fan Control - Melted Connector & Frozen Switch
 

Every electrical connector, on Honda cars, have some type of grease in the connector and then the connection is taped. Very few electrical issues on Hondas and I attribute it to the use of the grease, I am assuming it is a dielectric type grease. It was my assumption this grease would not conduct electric current but does keep the connection from corroding by keeping the oxygen from the connection. I think we are saying the same think different ways?

Re: AC/Heater User Fan Control - Melted Connector & Frozen Switch
 

The blower motor bearings might be dragging which increases the current demand. Check the motor to see if it spins freely.

Re: AC/Heater User Fan Control - Melted Connector & Frozen Switch
 

10-12 years ago, my blower switch and connector melted the same way. I found that the ground wire from the blower motor to the firewall was not getting good contact. So, I added a ground strap. Problem fixed.

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