Numerous Lighting Issues

[Casey Rayls]

1982 Long Bed K10 4x4. I've installed TWO new printed circuit boards from LMC. (I assumed one board was bad)

All twist in sockets/lamps work alone (out of the dash cluster) they check good and will light with direct 12 volts from a battery.

Only the bright/dim lamp will work on the dash cluster (see pic). No other lights work, but all have working bulbs and strong ears to make contact with the P/C board.
The old, ratty printed circuit board worked fine before !

Head lights go out completely when floor dimmer is depressed. Come back on when dimmer is pressed again. Replaced dimmer switch and same issue, so not the dimmer switch, guru.

Now, last night, the head lights started blinking slowly when driving !

When I turn the headlights off and back on, and they will work as normal again for a few more minutes before going to a slow blink again.

Taillights and turn signals all work, but won't blink in the cluster, though I can hear them blinking.
Interior under dash and over head lights work as normal.

 

[Ricko1966]

The reason your headlights are blinking is there is a short or high amperage draw on the headlight circuit. There is a breaker in the headlight switch itself that makes the headlights lights blink instead of just shutting off. It's a safety feature and an item I don't like about certain aftermarket harnesses that use a fuse in the headlight circuit,so a short in your lights means instant and total loss of headlights. Instead of blinking headlights to let you slow down and get off the road safely.

 

[83Stepper]

Head lights go out completely when floor dimmer is depressed. Come back on when dimmer is pressed again.

Bad dimmer switch on whichever side cuts out when pressed.

Disconnect the plug on the dimmer switch and check for continuity between all 3 terminals in both positions, high and low beam, to start. A short to ground in the floor dimmer switch will cause the headlights to go out when the dimmer is pressed among other general weirdness. Check for signal between the connections and for a short to ground. My headlights did the same when switched to high beams because of a faulty floor dimmer. One wire coming in is power, one outlet goes to low beams, other is to high beam. Dimmer switch is grounded through the body of the switch to the floorboard.

Can't say much else for the rest of it, but I'd start there at the bare minimum.

 

[Casey Rayls]

Replaced dimmer switch and it still has the same issue, lights going completely out when dimmed, so not the dimmer switch.

No one has EVER ran into my same problems in any forum for anything !! AhhhhGGH !

 

[83Stepper]

Replaced dimmer switch and it still has the same issue, lights going completely out when dimmed, so not the dimmer switch.

No one has EVER ran into my same problems in any forum for anything !! AhhhhGGH !

Did you test the switch before replacing it?

Circuit for the headlamps is pretty simple. Hot wire from the fuse block goes to the headlight switch. Wire from the headlight switch goes to the floor dimmer then carries through the firewall at the bulkhead connector to the headlights. Without knowing what's going on exactly, you'll end up continously throwing money and parts into it.

These old trucks do require some fairly simple but time consuming troubleshooting and a lot of times it's ground related. If the low beams aren't working, check to make sure you've got power at the headlamp socket. If you don't, test for power from the point of origin and trace back to the headlight.

Check to make sure you're getting power to the floor dimmer switch. Then check to make sure it's coming out of the dimmer switch to the bulkhead connector going to the firewall. If that's good, test the wire at the headlights for power. This will tell you if it's a break in power or some other issue.

 

[fast 99]

Vehicle has multiple problems attack them one at a time. Get a wiring diagram and start tracing circuits out. Be sure and follow grounds. A bad ground can cause feedback. Check the wiring plug for cluster is wired correctly and matches printed circuit. Most of the wiring on these trucks is a basic circuit, switched power, load and ground, nothing tricky.

 

[Hunter79764]

I'm going to throw out there that the main grounds need to be checked. If the body isn't grounded well to the chassis, I could see some of this "weirdness" happening. You can check voltage from the body to the battery when the headlights are "on" but not functioning, if you have more than a few tenths of a volt, you need to increase your ground strategy (body to chassis, chassis to engine, engine to body, and all of them to battery ideally).

 

[Casey Rayls]

On dimmer switch No. 3. Lights still go out when dimmer is depressed. I can plainly see lights are on, when on high beam, but test light won't light when applied directly to the headlight posts ! Try the test light on the battery and it works. This proves the test light is good.
If the ground to the body/chassis was bad, nothing else would work. You guys aren't helping much.
**All dash lights now work. No reason at all, they just started working after 3 weeks.

 

[fast 99]

You guys aren't helping much

Really?

Theres a bunch of knowledge here on general repair and SB specific. My personal knowledge base goes back 30 years as a line tech. With that attitude not wasting my time on you.

 

[83Stepper]

Did you test the switch before replacing it?

Circuit for the headlamps is pretty simple. Hot wire from the fuse block goes to the headlight switch. Wire from the headlight switch goes to the floor dimmer then carries through the firewall at the bulkhead connector to the headlights. Without knowing what's going on exactly, you'll end up continously throwing money and parts into it.

These old trucks do require some fairly simple but time consuming troubleshooting and a lot of times it's ground related. If the low beams aren't working, check to make sure you've got power at the headlamp socket. If you don't, test for power from the point of origin and trace back to the headlight.

Check to make sure you're getting power to the floor dimmer switch. Then check to make sure it's coming out of the dimmer switch to the bulkhead connector going to the firewall. If that's good, test the wire at the headlights for power. This will tell you if it's a break in power or some other issue.

On dimmer switch No. 3. Lights still go out when dimmer is depressed. I can plainly see lights are on, when on high beam, but test light won't light when applied directly to the headlight posts ! Try the test light on the battery and it works. This proves the test light is good.
If the ground to the body/chassis was bad, nothing else would work. You guys aren't helping much.
**All dash lights now work. No reason at all, they just started working after 3 weeks.

Sorry you feel this way. We all get it, diagnostic testing can be troublesome and aggravating at the same time. If you have power at the floor dimmer switch, yellow wire (signal wire from headlight switch), you should have power at both the tan (low beams) and light green (high beams) wires depending on position of the switch. If all three of those have power when applied to them, then go to the engine bay and use the ground wire there to test the headlight when it's powered up and working properly. If no light at the tester, then ground is bad. Try moving the ground to the battery post and repeat. If the light works, bad ground. Clean the ground location and wires. Check the wire lead connections at the headlight and continue from there.