Smoking Dimmer Switch

[dj31499]

91 Jimmy. Replaced my dash lights with some LED's. Had some cheap-o amazon ones in there, bought a few Sylvania 168's and liked how bright they were so I decided to get some for my I/P. I swapped them out and wasn't getting any light. Checked the 5 amp instrument light fuse and it was blown. Replaced it, still no light. Started adjusting the dimmer switch and it started to smoke and it popped. I thought that maybe the lights were trying to draw too much power (even though they're rated for less wattage than a typical 168 incandescent). Put the cheap amazon ones back in that had previously worked up until now, same problem: no light and as I turn the dimmer switch towards the brighter end, it gets to a point where it pops and smokes. Dimmer switch is about a month old, but I still had my old one (worked fine, but the wiper on the switch was worn and would cause the lights to flicker sometimes). Plugged that one in, same problem. I've attached a video of what happens (the I/P isn't plugged in because I was trying to eliminate that as an issue). Headlights, taillights and all other lights work fine, just no instrument panel lights.

From the wiring manual, it looks like the LT GREEN wire on the switch controls the high setting on the dimmer switch. Is that where I should check for a short? There are two other terminals (10 and 12) that don't show what wires feed them. Does the dimmer switch get power from one of the other 4 terminals on the plug? I feel like if there was a short on that section I wouldn't have headlights, taillights etc. Let me know what you guys think

 

[CT-BLAZER]

Tough to comment on with out seeing the schematic....

A test light looking for power would be a simple exercise. Start at IP & then switch.

If recollection is right that rheostat adjustment dims dash and interior roof light?

Smoke says burnt parts....that should be an easy search

LEDs are supposed to use less power ...tried some cheapies in my car.....dimmer than incandescents & they trip the dash computer.
They have to go

 

[Blue85]

Are you working from the front of the cluster or the back?

I would pull all the LEDs back out and see if the problem remains (especially if you are working from the front). They are polarized, but if one is backwards it won't cause a short - it just won't light. But it's possible there's a bad one in the batch that is shorted internally. It's also possible you have one of the sockets partially installed or a foreign object in one, such as a broken-off lead from one of the bulbs. Pulling each socket could identify that by process of elimination.

Now that you've swapped the switch, look the socket over for any signs of a backed-off terminal that could be touching something else. Having some melting happen in that socket sounds familiar. This is all based on the simple premise that the latest things you've worked on are mostly likely the issue.

 

[dj31499]

Are you working from the front of the cluster or the back?

I would pull all the LEDs back out and see if the problem remains (especially if you are working from the front). They are polarized, but if one is backwards it won't cause a short - it just won't light. But it's possible there's a bad one in the batch that is shorted internally. It's also possible you have one of the sockets partially installed or a foreign object in one, such as a broken-off lead from one of the bulbs. Pulling each socket could identify that by process of elimination.

Now that you've swapped the switch, look the socket over for any signs of a backed-off terminal that could be touching something else. Having some melting happen in that socket sounds familiar. This is all based on the simple premise that the latest things you've worked on are mostly likely the issue.

Working from the front (pulled the cluster out to put the bulbs in). The new Sylvania bulbs are polarized, so I figured that may have been the problem initially. But the video I posted is with the I/P unplugged and out of the truck; I made sure the connector isn't touching any bare metal when I would turn on the light switch. Both switches I've tested this way. And both of them have the same issue. Neither of the switches have burnt terminals, but I'll have to take a closer look at the connector itself to see if I find anything burnt. The connector looks fine, but I'll check out the connectors inside.

Some of the wiring diagrams show an internal circuit breaker in the switch, I'm wondering if this is blowing as I turn the dimmer switch. Either way I feel like I'm going to have to get a new switch but I don't want to smoke a new one out until I find the issue. The fact that it's blowing without any load from the I/P makes me think there's an issue with the amount of power being supplied to the switch.

 

[Wes Harden]

Iirc the power for the headlamp switch goes first to the hi low beam switch, which also provides the ground.
I think the Sylvania super brites are ok, I have an instrument panel full of them. If anything the LEDs are using less current.
Something did change though, and smoking components normally means high current draw, or high resistance in that circuit.

 

[dj31499]

Iirc the power for the headlamp switch goes first to the hi low beam switch, which also provides the ground.
I think the Sylvania super brites are ok, I have an instrument panel full of them. If anything the LEDs are using less current.
Something did change though, and smoking components normally means high current draw, or high resistance in that circuit.

Good point Wes. That dimmer switch is actually the connector mounted on the column for the hi and low beams. It’s got nothing to do with the dimming or the rheostat on the headlamp switch. The wire that feeds the input on the switch for the rheostat is no. 44, which is a dark green wire that runs directly from the 5 amp instrument lamps fuse to the switch. So that’s probably where I should focus my attention.

 

[Wes Harden]

the switch feeds the 5amp instrument fuse not the other way.

 

[dj31499]

Found the issue: I unplugged the grey wire coming from the fuse block. From the book this is supppsed to feed the radio light, convenience center, heater control light. It’s spliced in somewhere with the dash lights as well. As soon as I did that, no more popping of the fuse, and the light in the heater control worked fine. So my short is definitely coming from there. Going to have to see where it’s shorting out from there. Thanks for the help guys