New headlight switch smoking

[Warlordfrog]

I replaced the master headlight switch on my 1987 1044. When I turned it on, the new switch started smoking. The previous one was not working so thought a swap would fix it. The S3 is new and there is power to the F post on the S3. The truck has an aftermarket supplemental grounding harness. Bad ground somewhere? Other ideas?

 

[Action]

Push button light switch?

 

[Warlordfrog]

No. It is the standard three lever switch.

 

[Mogman]

Not a grounding issue, you have a short somewhere, damn I wish I had come up with the grounding kit, first thing everyone buys when they have electrical problems and is totally unnecessary, I think some think it helps when in fact they accidentally correct the actual problem while installing it.
It sounds like possibly someone has bypassed the breaker, it should protect the switch.

 

[86humv]

Switch has a breaker built in...If its a US made one.

 

[papakb]

Mogman, I differ with you on the necessity of adding the grounding kit to our trucks. While your basic principle is correct about the trucks original design being fully functional, who can say what's these things have been thru over the years and how much of the original bodies bonding is still working as designed? We all know that corrosion and oxidation take place on a continuiny basis and there's not much you can do to stop it so why not add a little insurance to avoid potential problems that ageing can bring up? We all know getting older sucks!!

 

[Coug]

I think it's more that it's supposed to be supplemental, not a replacement for the original system grounds.
Even with a little age/corrosion, all the electrical should still work. If the corrosion or other issues have gotten bad enough that the electricity won't flow properly, then those issues need resolved.

 

[Mogman]

Mogman, I differ with you on the necessity of adding the grounding kit to our trucks. While your basic principle is correct about the trucks original design being fully functional, who can say what's these things have been thru over the years and how much of the original bodies bonding is still working as designed? We all know that corrosion and oxidation take place on a continuiny basis and there's not much you can do to stop it so why not add a little insurance to avoid potential problems that ageing can bring up? We all know getting older sucks!!

The body is not used for grounding so body corrosion is not an issue, every device, light etc. has a ground wire that returns to a relatively low number of common bonding points, clean all these points and it will work as the folks that engineered the HMMWV meant for it to work.

 

[Retiredwarhorses]

The body is not used for grounding so body corrosion is not an issue, every device, light etc. has a ground wire that returns to a relatively low number of common bonding points, clean all these points and it will work as the folks that engineered the HMMWV meant for it to work.

you are spot on…and may I add, as many folks have an m998, the A2 and Turbo trucks, especially 400amp equipped trucks have all new ground points and completely different from the single point ground they used in the m998.

 

[TOBASH]

This debate goes back and forth every 6 months or so.

I like to know the actual harness works properly otherwise I fear fires. Bypass kits are great and I bought my M1025 already having one BUT I have spent literally hours cleaning all contacts. That effort helped fix many issues!

The harness bypass kit corrects symptoms but not the underlying disease. It’s a band-aide.

IMHO.

 

[Milcommoguy]

If one studies the prints and has been back and forth with a harness or two... it is easy to come to the correct conclusion stated posts 4 - 8 - 9 above.

Note too that the mechanical lighting switch requires NO ground. (not talking about the electronic one with built in smoke)

This is a selector to route plus 24 volts to the selected lighting (horn too) circuits. Those circuits to function correctly must have a ground return of course to complete the circuit. It will be a wire. Not the frame, not the body... But will terminate at one of the ground "tie" points noted on the drawing and that lead will route to the negative battery.

Unusual a switch of this design and the circuits it supports is not going to smoke. Its internal circuit breaker should handle design loads and trip. Would be interesting to see a picture or two... but trying to guess problems is frankly... guessing.

Not sure a band-aid... would fix a broken leg. Find and fix the leg first.

"LEG" refers to wire, lug, terminal, loose hardware, CAMO

Edited... NEW switch ?? China knock off or the real deal. Still guessing, CAMO

 

[WOLF DOG]

Lack of a ground will not cause smoke. Smoke comes from a short circuit or an overloaded conductor that is carrying more current than its size allows, which over heats causing the insulation to melt or burn creating the smoke. Loosing a ground makes an open circuit where no current flows, however a loose ground or intermittent ground could possibly heat up at the loose connection point, but not likely with only 24 volts trying to push the current. This is much different than a short circuit.

 

[blutow]

I figured I needed the ground harness for my 1123 when I first got it (based on so many posts saying it's needed), but then I did some research on how it's designed. At least for my 1123, the harness was just duplicating the factory grounds, so it seemed pointless to me and potentially problematic. Maybe the earlier trucks had a more troublesome harness or grounding points. Not only did I see the aftermarket ground harness as unneccessary, but I think some aspects of it are poorly executed and potentially dangerous. I believe the ground harness includes a small guage "ground" wire for both the starter and the generator even though both of these components are both grounded to the block and also have very beefy dedicated negative/ground cables. If for some reason the factory ground path on either of these components failed completely (doubtful, but possible), you'd be asking the very small wire in the aftermarket ground harness to carry way more amps than the wire is rated for. It's poor electrical design to have your ground/negative path "smaller" than your positive since they both have to carry the same amps. Beyond the wire size issue on those 2 big circuits, it's also generally bad practice to provide multiple parallel ground/negative paths. You really want a single "tree" structure where multiple grounds might feed into larger ones and eventually back to the battery, but paths should be minimized when possible. If you allow multiple "parallel" paths, you are prone to creating ground loop situations. I doubt a ground loop is going to do any harm to the crude electronics on a hmmwv, but can certainly cause interference if you are running a radio or anything with sensitive electronics.

 

[TOBASH]

Lack of a ground will not cause smoke. Smoke comes from a short circuit or an overloaded conductor that is carrying more current than its size allows, which over heats causing the insulation to melt or burn creating the smoke. Loosing a ground makes an open circuit where no current flows, however a loose ground or intermittent ground could possibly heat up at the loose connection point, but not likely with only 24 volts trying to push the current. This is much different than a short circuit.

A bad ground can force electricity through an alternate poor pathway. That causes smoke and fires.

 

[WOLF DOG]

A bad ground can force electricity through an alternate poor pathway. That causes smoke and fires.

Not saying you're wrong TOBASH, but could you give me an example? I just can't imagine a scenario where this would occur.

 

[Milcommoguy]

Not saying you're wrong TOBASH, but could you give me an example? I just can't imagine a scenario where this would occur.

I can answer that... When your PCB, Smart start box goes to lunch and smokes your glow plugs.

Ask me how I know, CAMO.... CAMOTEKSYSTEMS

 

[blutow]

Not saying you're wrong TOBASH, but could you give me an example? I just can't imagine a scenario where this would occur.

I also gave an example in my rambling above about the ground harness. When you add a small guage "supplemental" ground to the generator, nothing good can come from it. If the factory ground path fails, you have all the current of the generator having to flow through the supplemental ground. That supplemental ground turns into a red hot heating element in a hurry if the generator is running anywhere near max amps.

 

[TOBASH]

Not saying you're wrong TOBASH, but could you give me an example? I just can't imagine a scenario where this would occur.

Many examples my doubting friend. The most extreme is loss of engine ground. When you operate the starter, hundreds of amps look for a way to escape. The thin wires to gauges and aftermarket projects and such now become the only available pathways.

I suggest looking for more grounding issues and less examples.

Good luck.

 

[INFChief]

I would bet you have a short; crossed wires or unintentional ground.

My first inclination is to do a painstaking visual inspection of the harness. I’ve found that harness problems are most often at one end of the other and a close examination could easily find the problem.

Frankly, I would start with the trailer receptacle if equipped. A damaged receptacle or some half-baked repair from a mechanic might reveal crossed wires.

What condition is the headlight canon plug in? Did someone put their bear claws on it and twist the snot outta it causing wires to fray through and touch or arch across?

Did someone install some sort of accessory (military or civilian in nature) and tap in to the wrong circuit?

A thorough visual and hands on inspection is the place to start.

It’s not too painful but necessary - break out your multimeter and start running continuity tests on each circuit.

I always disconnect my batteries before running OHM’s tests. And I’m in the habit of checking for voltage on each circuit prior to attempting to check for OHM’s. A blown fuse in your meter is annoying and preventable - but it becomes aggregating if you don’t have any spare fuses.

Unless I’m specifically testing through a component (dimmer switch or turn signal relay) I disconnect the harness from that circuit.

I check from one end to the other (others if it’s a multi branched circuit) and I also check from one or both ends to ground to verify it’s not grounded if it’s not supposed to be.

I’m sure this is frustrating and getting expensive but go back and do the inspection and then run some continuity checks.

Please keep us posted!

 

[WOLF DOG]

Many examples my doubting friend. The most extreme is loss of engine ground. When you operate the starter, hundreds of amps look for a way to escape. The thin wires to gauges and aftermarket projects and such now become the only available pathways.

I suggest looking for more grounding issues and less examples.

Good luck.

So the "thin wires to gauges and aftermarket projects" would be the point of smoke ?