Headlight switch or lights Electrical question

[j_boucher]

So I made another thread for what I thought was a ground for the alternator mainly because my headlights would intermediately turn on and off. I cleaned all grounds and positive cables and took it out for a test run about 10 minutes into ride again headlights intermediately on and off , turn them off and back on again approx 1 minute later same thing . I'm at a lost , is there a ground for the dash somewhere I could have a bad light switch I guess however I swapped it out for the push button one a few months ago looked new never installed but who knows, and its only the headlights that blink no other of the service lights blink. Any advise ? Going to trace wire diagrams now

 

[Keith Knight]

What type of light switch do you have? Old lever style or new push button?

 

[j_boucher]

What type of light switch do you have? Old lever style or new push button?

New push button

 

[GeneralDisorder]

Check the switch ground lead first. Some of the early push-button switches were not effectively grounded and they revised the switch to have a larger and better connected ground strap and it MUST be securely grounded to the dash. It's a seperate ground wire all on its own - not part of the cannon plug.

 

[Mullaney]

So I made another thread for what I thought was a ground for the alternator mainly because my headlights would intermediately turn on and off. I cleaned all grounds and positive cables and took it out for a test run about 10 minutes into ride again headlights intermediately on and off , turn them off and back on again approx 1 minute later same thing . I'm at a lost , is there a ground for the dash somewhere I could have a bad light switch I guess however I swapped it out for the push button one a few months ago looked new newer installed but who knows, and its only the headlights that blink no other of the service lights blink. Any advise ? Going to trace wire diagrams now

.
You would be better off with the "three lever" light switch.
An American Made one for sure.
From a reliable vendor...

 

[j_boucher]

Check the switch ground lead first. Some of the early push-button switches were not effectively grounded and they revised the switch to have a larger and better connected ground strap and it MUST be securely grounded to the dash. It's a seperate ground wire all on its own - not part of the cannon plug.

Is it located near the cannon plug?

 

[j_boucher]

.
You would be better off with the "three lever" light switch.
An American Made one for sure.
From a reliable vendor...

Think I may swap my old back in and see if it works

 

[GeneralDisorder]

Is it located near the cannon plug?

It's on the body of the switch and should be spliced to the existing ground and the existing ring terminal serviced or the whole ground wire and terminal replaced. They come like this. The large black cable with the ring terminal is the switch ground. Without that ground the switches will burn up.

 

[Keith Knight]

Definitely start at the switch. My push button had issues in the beginning. Took it apart cleaned it added the ground and works great now.

 

[j_boucher]

so I added ground wire it did it again , replaced with my old switch .... did it again . I don't know where to start for this and its only low or the high beam that cycles on and off , lights are steady then it just starts slowly turning on and off . turn the switch off then on again its fine for a moment and then it started to blink again . I decided to time it but didn't prove anything one time it did it at 3:27 another at 57 Secs . no other electrical items on when it happens just the main switch , going to go try just turning lights on engine off and see what happens

edit update ---

Test 1 Master switch off lights on after 5 min no issues

Test 2 Master switch on engine off lights on within 3 min headlights turning on and off

I guess something is back feeding it don't know what it could be , I swear the older I get I get more and more complex troubleshooting issues seems the gods just want to test me.

Anyone have possible input to the issue please help out "thanks in advance" in the meantime headed to wire diagrams for the night

 

[Keith Knight]

Sounds like something is warming up then causing the problem. Check the fuse maybe pinch the terminal so they are tighter. Also remove the resettable fuse with a standard fuse. If that doesn’t work swap relays. One thing at a time though so you know what the solution was.

 

[Ronmar]

Pull relay K07 and install a jumper wire with 1/4” spade terminals between pin 30 and 87 in the relay socket. This will turn on your headlights and take the light switch out of the equation for testing.

If the lights work ok this way, pull the jumper and move relay K20 to the K7socket and use tge light switch to turn on the lights. This will eliminate or confirm K07 as the possible fault, or again point you toward the switch seivh powers K07…

 

[hike]

So, all marker, brake, blinker lights, work fine as the headlights alone blink inappropriately? Are all the lights LED, incandescent, or mixed?

[edit: I wish I was as smart as @Ronmar}

 

[j_boucher]

So, all marker, brake, blinker lights, work fine as the headlights alone blink inappropriately? Are all the lights LED, incandescent, or mixed?

Yes just the headlights All are incandescent /Looking at wire diagrams and it hits two relays



Wonder if the headlight relay could be bad .... going to keep tracing wire diagrams

 

[Ronmar]

Here, this should be a little easier to follow…

 

[j_boucher]

Here, this should be a little easier to follow…

View attachment 926711

Thank you

 

[j_boucher]

Does anyone know where the P27 / J27 is



Wire diagram just says Chassis front

 

[j_boucher]

So I think I may have fixed it I swapped out the K-8 relay mainly because the light indicator in dash would also blink on /off with the lights and that circuit is connected to 87 on the relay / I ran the truck for 1/2 hour just idling and the problem is gone will take it to store later today . Cross fingers its gone and thank you for all who helped

I wonder if the not grounded switch was the culprit to the relay ? I will keep my old switch in till I know its fixed

 

[Ronmar]

well if you had high-beams selected/on when it was cycling, the dash high-beam indicator would cycle with the headlights going on and off, either caused by the light switch or by K-07 cycling... Did you jumper 30-87 on K-07? that will effectively bypass the light switch and test all the other wiring in the headlight circuit...

Anyone who owns a LMTV should have a couple 3" jumpers made with 1/4" male spade connectors crimped on. You can make a lot of things work in a pinch with a couple jumpers...

P27 may be under the passenger dash, or under the power panel. I know the connector(P51) that feeds the rear bumper/taillights is under the PDP in the dash...

 

[j_boucher]

well if you had high-beams selected/on when it was cycling, the dash high-beam indicator would cycle with the headlights going on and off, either caused by the light switch or by K-07 cycling... Did you jumper 30-87 on K-07? that will effectively bypass the light switch and test all the other wiring in the headlight circuit...

Anyone who owns a LMTV should have a couple 3" jumpers made with 1/4" male spade connectors crimped on. You can make a lot of things work in a pinch with a couple jumpers...

P27 may be under the passenger dash, or under the power panel. I know the connector(P51) that feeds the rear bumper/taillights is under the PDP in the dash...

If it comes back I will using the jumper. I made a few of them this am