Headlight switch from hell

[catfacekia]

My 89 MGM had what I thought was the typical autolight switch failure awhile back but when I finally got around to changing it, I found a bigger issue facing me. The larger of the two connectors for the switch had a melted spot around just one of the connection points and the wire behind it had melted. I bought a new connector and wired it up, only for it to melt AGAIN. This time when it melted I noticed that the lights we're on(still no headlights, but parking lights and tails) and the switch was in the off position. Does anybody here have experience with a similar issue, or understand electrical enough to point me in the right direction? I'm one step shy of sending it off to a shop and having the lights hardwired to a switch panel to bypass whatever is going on.

[GM_Guy]

Typical failure. All I can suggest is buying a good quality connector and making sure that when you splice onto the wiring, that you cut the burned wire back far enough that you are into good copper to splice onto.

Alex.

[catfacekia]

So that's the only thing still preventing my headlights from working? No doubt?

[jaywish]

When you have the switch out and the wires repaired, reconnect the battery lightly and see if any lights come on. If so, disconnect battery and find the problem.

[gadget73]

yeah, its common unfortunately. The other place that develops issues that keep the headlights from coming on is the large connector on the driver's side fender, right near the soup can. Thats the connector for all of the wiring in the header panel. The marker lights and headlights pass through that. When the connections there get shitty the headlights or other lamps can stop. If you find a melted terminal inside when you unplug it, fair bet its the headlights. The usual fix is to clip the burned wire on both sides of the connector and splice a new piece around the damaged connector.

I'd add a relay harness to unload the switch. Feel free to swap other exterior lighting to LED for the same reason. The stock wiring is a bit on the feeble side, and time has not improved it. The relay harness takes the headlamp load off all the switches and bumps the voltage to the lights for better output.

[catfacekia]

I'd add a relay harness to unload the switch. Feel free to swap other exterior lighting to LED for the same reason.

Are you saying that it would be wise to just rewire the headlights altogether? I'd like to get auxiliary lights and things in the future so a switch panel will surely be added at some point. It couldn't hurt to do it now and have some piece of mind.

[jaywish]

Basically you use the stock wiring to activate a relay and pass a new fused power line through the relay to the headlights along with a comparable new ground.

[catfacekia]

I would be all for doing that stuff if electrical work didn't scare me and confuse me as much as it does.

Does this issue typically come with the battery ground sparking when you connect it? Because I've noticed that issue as well.

[gadget73]

The relay harnesses are a plug-in thing. You unplug the 4 headlamp connectors. The relay harness comes with 4 new headlamp connectors and one plug that goes into one of the originals. + feed goes to the battery, - to ground and now the only thing the headlight switch does is turn a relay on. Power runs straight off the battery instead of through 2 switches and a bunch of 30 year old wiring connections. If you can change a headlamp switch, you can install a headlamp relay harness. Typically it bumps light output too since there isn't much voltage drop without running through all that wiring. I got about 2v more on my Towncar, and my Continental will be about the same. I've measured voltage drop from battery to headlamps in that car at 2.2 volts.

I've got a cheapie harness on order from China, should be here next week sometime. Once it shows up and I give it a look-see I'll let everyone know if its junk or not. The one I got was under 20 bucks on ebay so I don't expect miracles, but it might be serviceable. Its going in my Continental, but that car wants the same sort of harness a full size car gets.

In the meantime, eyeball the all of the connectors. Its not rocket surgery, the connections just have to be clean and tight. If you see signs of melted wiring, thats a bad connection. Poor connections have high resistance, and high resistance makes heat. Check the switch in the column too. For headlights, power goes from the headlight switch to the multifunction switch, from the MF switch out to the lights. If either switch or the connections to them are bad, you'll get nothing.

Battery sparking when you connect it is just some load. Door lights, hood light, ECM, etc.

[jaywish]

Oh I didn't know pre-made kits are a thing. Should have figured that was what you were talking about in the other thread.

[catfacekia]

I checked that connector in the engine bay by the soup can and found a burnt terminal. I don't see any melting on the connector or external wire damage.

[gadget73]

Can you tell what color wire it is? Light green / black is the high beam wire, red/black is the low beam one.

[catfacekia]

I'm pretty sure it was a yellow wire...