how to test wire troubleshoot GM headlight switch 

I’m having marker light problems, why?

How did you fix it? Did you replace it?

those switches usually always work, but the resisted spring sometimes stops working correctly.. thats why i made the video.. because once i started going through my car i realized that switch was not as simple as "people" say it is

its a thermal switch that is also a breaker like you said if it gets too hot

I just got a 71 with the same problem, did you ever find a solution? I have changed the fuses, the bulbs, and the h/l switch... No luck so far.

Same problem here on my 72 buick GS.. I was told if you use a test light and pull the rod on the 1st stage its suppose to distribute power.. but if no wires except the red has power then the switch is bad then the 2nd pull of the rod.. the blue wire (headlights) will have power

Great job.

I would get a new switch if it does that

Haha.. I was wondering the same thing. I assume you're referring to the jam from about the 4min mark to around 8min (before Sabbath kicks in).. I'm not sure, but I agree it's kinda American Analog Set-ish. Also, thanks Chris! I totally fixed my original switch & didn't have to replace it, thanks to your thorough video. You rock, man!

put it to the the right

Same question I had. He used a car battery

+Rhett Burk clean up the grounds on the harness and check chassis ground from battery

I would start by taking each 1157 signal bulb out.. and making sure it is clocked in the socket 100% the right way

I got the c30 project started I will go over it again soon .. thanks

This probably a little late but make sure your ground connections are good, if they're go ahead and test the wires, also make sure you have a good battery connection

Okay I know I just posted this but I also just figured out by process of elimination that I have a bad dimmer switch which wasn't creating a signal to the headlights. Problem solved

i used to drink in my early videos and i thought it was cool to act ignorant.. i did go back and watch that and i thought it was funny.. i ended up greasing that switch with the dielectric grease and it has been on my car since the video.. some people claim they cant buy a switch for their vehicle.. i dont act like that in real life, though LOL

@@chriscraft77022 I did appreciate the video. I have that same switch that I will take apart tonight so it was very helpful to see it. I liked the humor. If you haven't watched any of user "Ave"s video....you should. He is funny as hell and I thought of him when I watched yours.

first thing, locate the 2 grounds on the core support (off the wiring harness) and clean them up... second, check the chassis ground to the front fender from battery negative terminal... BASICALLY.. check the grounds to start with.. there is no headlight relay (unless that car has one and i dont know about it) im pretty sure thats the horn relay you are talking about

Chris Craft your right, that's the horn relay I was talking about on the driver side inside fender... Why did I say headlight relay?! I don't know what's the matter with me.. ;) that was MY mistake... I'll check into that what u suggested to my reply... Thanks... I'll get back to u... Right now my car is at the shop getting brakes done... JEFF

just clean up the grounds.. get an assembly manual if you can to see where they all are... thats where i would start and hopefully where the problem is

there is a small button .. push handle all the way in... push the button and pull it out

does that truck have the foot button in the floor to the left of the brake pedal or does it have it on the blinker switch? to turn on the high beams?

@@chriscraft77022 there's no foot switch and I'm not sure if the blinker switch controls the high beams. As faras i know i thought the light switch it self controled the high and low beams , because it clicks twice when pulled I'm learning as i go with the truck......

@@marquesmoss5283 on the blinker switch you push it forward.. to engage the high beams.. check it out

@@chriscraft77022Thanks for the help.Turns out you have to pull the switch all the way out and the pull the turn signal lever back to engage the high beams. That saved alot of time trying to go threw and check all the wiring.

if you are gonna run a relay the light switch doesn’t have anything to to with that.. find the wire that feeds headlights ( by headlights) that’s what you run to 86 to turn on the relay

Thank you for your help

usually not the switch.. check grounds... first..

@@chriscraft77022 Thanks, I replaced the courtesy relay and the center console printed circuit, got them working now.

are you saying like they dont sell an exact repro of yours?

+Chris Craft Yes

Joe Rogerio I have a 73 electra all lights work but headlights. You fixed your problem, lmk

ground only goes to 1 place on DC .. what’s my grounds explained video

thermal breaker.. yeah

@@chriscraft77022 Thanks! I was going to add one in the circuit , now I know it is not necessary. Never knew that.

you need to take the headlight grounds off and clean them.. there should be one for each headlight

I know this is old, but I figured if share my experience. I rewire these squares a lot. There is about a 15amp breaker built in to the switch. It's so that if there is ever an intermittent short you won't just blow your fuse and lose them. But it sometimes with cars that actually turn on 4lights when on high will overamp the switch, I think there was a different breaker installed on some vehicles with 4headlamp switches at one time. But since gm uses small wires on some, they default the all switches to the 15amp instead of 20. I used a 91 core support+grille in my 85 K10 shortbed after my 350 was built. And the headlamps are usually wired to the winners for high. And the outters for low. I used a relay with the high to backfield the lows with the power from firewall with 14awg wire and a 25amp fuse so that the swiths actually don't carry all that load when in high. And only in lows. Which on 2 headlamp systems, it works like a tailight bulb. There is a 45w filament/and a 65w filament the ones with 4 are either top ones with two 45w filament. (One aims down; ones up) and the lower one's are 50w. The 89-91 grille has two like on 92+ where it's outer at 55w and inner at 65w.

@@t-rodshader9593 I’ve got a 1976 Chevy Itasca RV on a Chevy p20 chasis, the system is a 350tbi. After I got a new alternator put in my gages spin crazily, they ALL spin besides the battery gage one I’ve noticed. I’ve gotten it looked at by 2 mechanics and the wiring is fine according to them, they say it’s the cluster panel itself but I struggle to understand that as they were working perfectly fine before the new alternator. Also there’s a green wire, it was connected to something then I discovered it burned off at the end. I also noticed there’s two green wires coming from the headlight switch if that matters at all, dark green and light green. At this point I’m wanting to check it all out myself, do you have any advice?

@@briizcustoms9543 is the wire you seen burned outside under the hood?.. it could very well be a link to something interior related, but I have a feeling you may have lost a ground somewhere and found path through a wire too small and burned it, either that or since you did just replace the alternator, and I've seen this more times than not, it overcharges at some point, and if your not paying attention at that very moment for however long it can put out 19volts and you'd never know without the lights on or it being high enough to burn out the ignition coil so alot of times fuse links will end up burn led and cause weird things to happen or loose power to certain things from the battery or to the dash inside.. I'll have to look at the diagram for the chassis and see what I can find.. that is interesting and sounds a lot like a ground issue🤔

@@t-rodshader9593 Let me know what you find, the mechanic claims he fixed it so I’m just waiting to get the RV back to see

they are supposed to do that .. they are literally lights you left on when you parked the vehicle at night

why not buy a new switch they are like $15 ...

@@chriscraft77022 where at

if i had a 94 cadillac i would just change the switch out first and then go from there.. i cut out at 88 and then jumped to 2003... in other words i have never messed with anything in between so i have no idea

Thanks Chris, I plan to replace the switch ASAP, is there anything else that may cause the dash lights to go out?

check the grounds to the dash frame

@@chriscraft77022 hey Chris I have an 83 chevy caprice and the dash light headlights tail lights and radio all just went out what's the cause of that

its usually never the switch.. but it could be,,, you have a TAIL LIGHT fuse .. and if thats good check the grounds for the tail light harness over by the tail lights.. you should have 1 for each light.. let me know what you find out..

@@chriscraft77022 I will be in touch thank you for the fast reply

you have a high beam switch... probably on your steering column with the wiper switch... not 100% sure because I have never messed with Buick’s

Check grounds on headlights there is one for each

this switch has nothing to do with that

Ok see when I flip the switch non the brake lights don't shut off or don't work if the switch is in but the brake switch is new and i checked the harness from the box to the rear harnesses and it's fine can't figure out why it's doing that and the harness for the tail lights is new it's on a 1978 Buick regal

the brake lights are also the turn signals and hazards.. same filament side on the bulbs .. check the hazard lights first

How many wires are in the plug??? 🤔

Chris Craft wasn’t sure if the harness has been messed with. For some reason the headlights and hideaway doors open in the parking light position. Parking lights stay on in that position but then full out parking lights turn off as they should.

buy a $10 wiring diagram from speedway racing

well, dont hate me for trying to diagnose your problem without seeing the car... but have you replaced the switch, #1... ? if you have, check to see if someone, or YOU... have ran accessories off the 10 or 12 gauge fat power wire to or from the switch.. when weird things happen, usually cause someone spliced into wires throwing off what was engineered... those headlight switches have a weird contact that only send power one way... and affecting the amps could make the switch overheat and do its job to break the circuit... because they are unfused from the battery..

thanks

If the car came with normal incandescent bulbs and you "upgraded" them to halogen, that will cause the switch to shut off due to too much current draw.

only low beams come on with the pull out switch..