Wiring Success...and a New Problem

Update--

Smoke was coming from the new light switch. I unhooked the connector after seeing wisps of smoke. The ceramic collar that holds the dome light "on/off" switch became extremely hot. I now suspect a short in the dome light circuit, but there could be a problem with any circuit on that switch.

Carefully check for a wiring error within your repairs. Also check wire bundles for melted insulation and shorts that may be hidden. This secondary damage could have occurred during the fire as wires were burned and faulted.

Jim:

Thanks. I did it--tracing the wires wherever I could access them, and also checking resistence with the tester on all wiring. I know the switch splice is clean; believer the rest of the wiring to also.

I tested again and isolated the tiny emission of smoke to the new headlight switch. The back of the switch gets too hot to touch, especially around the ceramic shield and dome light actuator switch.

I have developed a new theory, with the help of an article by Mike D'Ambrogia, lined on the IFSJA website, that the Halogen headlights with which this GW is equipped are at fault. They draw too much power and overheat the switch. I am fairly certain that the 1984 Grand Wagoneer was NOT originally equipped with these much brighter lights.

RB

Halogens will wear out the switch for sure, but they will blow the internal breaker before smoking out the wires. You have a short still or the plug is bad inside so the contact to the switch isn't tight. A arc will heat it up fast and smoke it.

Mike

The ceramic collar holds a wire coil, that is the attenuator for the dome and instrument panel lights. An attenuator converts unwanted voltage into heat. This is not the best design, but it is the simplest. It may smoke after installation, and it may become hot with the dome and instrument panel lights dimmed, but I don't think that "extremely hot" is a description of proper behavior. The collar is ceramic so that it can stand the heat. That appears to be a separate issue from the fuse blowing on the dim headlight setting. Can you disconnect the dome light circuit, and try again? Can you rig up an ammeter in the circuit? Clip on ammeters are great, and make great gifts too.

Earle

It could well be that, because the switch was newly installed, the little wisp of smoke was just the switch getting "burned in" and perhaps there were traces of oil on the ceramic heat sink. I also noticed this morning, that I did have the dome and courtesy lights switched to "on" which may have contributed.

All is seemingly in order now, with thanks to all here who guided me through this frustrating but interesting project.

RB

You're no doubt right. Lurking in the background of all this is the thought that I may not have corrected the condition that caused the fire in the first place. Seeing even a wisp of smoke was enough to cause me to panic after that,

I believe I will start over again tracing power to that switch and recheck the resistence in the wires on the switch

RB