I've read all the previous posts on headlight switches but cannot find an answer to my question. I've replaced the entire wiring harness and am troubleshooting the last few issues. My LED parking lights do not come on when the headlight switch is in the parking light detent (first stop pulling out). The lights themselves, front and back work when the turn signal is activated or the hazard switch is activated. I've replaced the headlight switch and the same thing is happening. LED Headlights work in the "lights" detent (last stop on pull), dimmer switch works
I checked the circuits with a test light and while there is power to the headlight switch, there is no power on the rear of front parking lights terminal on the switch. I was reading my manual and it shows a fuse block on top (or bottom) of the headlight switch. I do not have a fuse block on my switch. The old one had it but neither of my two new ones (LMC and Dennis Carpenter) did. The new harness has a complete fuse block for the entire harness,

Question #1. Do I need a fuse block on the headlight switch?
Question #2. Do ii need to run a separate ground wire from the headlight switch to a chassis/frame ground?

Any help would be appreciated, I'm pulling what little hair I have left out because of this.

 

Not necessarily. The old switches had them, but the more modern switches used a self-resetting circuit breaker inside. Perhaps the new replacements for the old switches are using that design.
It might even have been mandated for safety reasons.

No. Normally the light switch is just a pass-through where it opens and closes the pathways. So grounding the switch itself is not required.
But it can't hurt either, since the switch was originally mounted in a metal dash anyway, simply making sure it's grounded does not hurt anything.
It's always good practice to make sure that the dash panel itself is well grounded to the rest of the body. Helps the gauges and any other stuff that needs grounds work better. Also helps reduce radio noise.

Regarding the grounding of the switch itself, I really am not that familiar with the older switches to know whether or not there is the requirement of a ground. Just going on what I know about later switches ('66 and later mostly) but if it grounded through the dash before, it should still do so without you adding a ground jumper. Wouldn't know where to attach it anyway!
If you freshly painted the dash, or it's totally rusty on the back though, I would attempt to clean that up so that the switch has a good contact point with the grounded dash.

Just FYI the main ignition switch is usually grounded. Has nothing to do with the accessories working, as those are still the standard "pass-through" circuits where the switch is just there to open and close the circuit. But most switches back then had what was called the "prove out" or "proof out" circuit activated in the START position. This circuit grounded to the dash as a method of checking function. Was often used for stuff like the brake warning lamps in later vehicles as an old-school way of testing the lamp at each startup.
But as said, the light switch does not normally need a ground. Maybe for the rheostat for the dash lights? Dunno but someone will.

Good luck.

Paul

 

Regarding the switch, maybe take your meter down to the parts store and check a third switch. I've read where people have had two, three and even four bad switches in a row!
If power is going in, but not going out when it's supposed to, then the only thing it could be in my mind is the switch itself.

Of course, that doesn't mean I'm right! Just means it's one of the possibilities higher up on the list hopefully.
After all, finding a bad switch and getting a new one will help you keep some of your hair!

Paul

 

I think the headlight switch has 2 power supplies, one that is hot from the solinoid and one that comes from the fuse panel. Do you have 2 hot leads at the switch?

Eric

 

EricJ, no there is only one hot going to the switch. Terminal B is hot wire from battery (black/orange). I am wondering though if terminal A, green/red brake switch feed is the other hot.

 

hi beam switch plugged in?

 

mulegal, yes hi-beam is lugged in and hi-beams work.

 

Ya you are correct, I was thinking it had a parking light fuse, but I looked and it does not. According to my wiring diagram the park light wire is brown, so you need to test that wire and see if it has 12 volts to it in the park position. If it does the switch is fine and you have an issue between the switch and the light sockets. Or bad grounds at both lights.

 

I checked both the front parking and tail lights terminals on the headlight switch with the switch in park detent. No power indicated. Looks like the 2nd bad switch in a row.

 

Let us know what brand and model number your switches were so we can avoid them in the future. I'd say this is getting ridiculous, but it's long since beyond that!
I remember well when you could just assume that the new parts you installed were not the problem. Now as often as not they ARE the problem or create new ones!

I have not looked at any diagrams to see if there is something funny about how the switches are laid out in this vintage of truck, but I wouldn't thing they're so different that you can't use the test methods you've been using. If you don't get power out on the terminal, it should mean that in fact something is wrong inside the switch. You know power is going in, it's just not coming out. Crappy way to find out about modern parts!

Anyway, curious to know if they were both the same brand. I'm getting to the point that I'd like to see everyone mark each defective part so that when you go to the same place to get a replacement part, you're not just buying someone's old mess that never got sent back to the manufacturer.
Seen that happen too, but hopefully it's not too widespread.

Good luck on the third.

Paul

 

I bought the first from LMC and the second from Dennis Carpenter. They look the same visually.

 

I found that Led bulbs did not work when switch in park position. They would work when headlights on. I put the old 1157 bulbs in and viola would work again. You can wire in a resistor to increase the load, which should allow the current to flow.
We had the same issues on traffic signals, when LEDS first came out. Because there isn't enough load it doesn't make a complete circuit. We would install a resistor or another bulb inline, which would solve the issue.

 

I finally figured it out thanks to one of the comments on this post. EricJ suggested there may be a 2nd power source to the headlight switch and based on my wiring harness instruction manual I replied there was only one and kept looking for an issue. After installing the THIRD headlight switch I had the same results; no parking lights or dome light. It just didn't make sense three switches from three different sources could be bad so I started fresh this morning just using simple logic.
-The bulbs all light for the turn signals and hazards so the wiring must be okay.
-The circuit requires a wire from the fuse block to post D1 on the switch. The wiring harness instruction say to simply run a wire from d1 to the door switches/lights and back to D2. It specifically said the white wire from the fuse block(#45) in the kit was not needed leading me to think the power for the dome light was coming internally from post B of the switch..
-Posts D1, R, and P all would not light the test light meaning they were not getting any power from post B because it was hot therefore there had to be another power wire for the switch.
- Back to EricJ's comment made me do a quick check with the white wire on post D1 and the parking lights and dome light lit immediately. Now I have two extra headlight switches, parking lights and a dome light.

Thanks to all the comments. I know sometimes I worry that my comments might not be right or worth mentioning. ALL comments are good and could end up fixing the problem.

 

Thanks for the follow-up and congrats on getting it working again!

Oh, but in a "by the way" kind of way, just because the hazard, turn signal and brake lights work, does NOT mean that the wires are good. Just means that those wires work.
These are separate circuits between the bright filament (brakes and signals) and dim filaments (running/parking lights) from the switch to the lamps. So separate wires all the way from the switch to the area of the bulbs, where they might split off to power the different lamp locations in that corner.

Glad you did some more digging and found the issue. A big win!

Paul

 

Which diagram did you find that gave you the details? If online, got a link to it?

Thanks

Paul