1980ish K10 3 lights then 1 light on press

[shovelbill80]

So as it turns out, don’t use AI for a wiring diagram. I was checking the wrong fuse. Found the correct taillight fuse and it was and still keeps blowing when I turn on the lights. Obviously I am not an electrical guy so what might cause the fuse to keep blowing immediately after replacing the fuse and turning on the headlights?

The most usual culprit is the bulb shorting in the socket... try to take the bulbs out (they may be 'fused' in)and look into the socket if you can. The 1157 bulb has 2 filaments, and the socket has the corresponding spring-loaded contacts. I'll wager the thing is all sorts of gunked up with grease, corrosion, and whatever else fell in there over time...

Check the reverse lights, too. That should be a single filament 1156 bulb.

 

[shovelbill80]

Don't forget to look at the license plate lamps...they're on the parking light circuit.

 

[kkgp81]

Quick update. Drivers side top headlight connector was melted.

This reinforces that you need to check your grounds.

 

[jbchevyfan]

Latest progress. Created a jumper with 20 inline fuse. Ran it from positive on battery to brown wire in rear harness. Taillights and license plate lights work great. Don’t that mean the ground odds good? Now, I cannot tell which wire is the “brown” wire from the bulkhead to rear. Was going to check for continuity from fuse contact through the bulkhead to figure it out but cannot seem to probe into the “presumed brown” wire or beside the presumed brown wire into the bulkhead. Getting close but thinking it might be the brown power wire to the rear.

 

[Snoots]

The taillight harness runs from right to left, then up the drivers side to the firewall. The main harness connects to the tail harness near the left rear.

 

[nvrenuf]

If your search wiring diagrams you really need to identify the year.

1980 is the older front end with only 2 headlights.

1981-82 are the newer front end but still only 2 headlights.

You couldn’t get a 4 headlight set up until at least 1983.

 

[jbchevyfan]

It is a 1979, 80, 81. Just saving an old work truck as a fun project. Rear harness seems to meet in the middle and up the left (drivers side) frame. It’s a k10. Just need to figure out how to check that last bit of the brown wire between rear and bulkhead. Put new bulbs in to be certain and they work fine with power direct from the battery.

 

[nvrenuf]

It is a 1979, 80, 81. Just saving an old work truck as a fun project. Rear harness seems to meet in the middle and up the left (drivers side) frame. It’s a k10. Just need to figure out how to check that last bit of the brown wire between rear and bulkhead. Put new bulbs in to be certain and they work fine with power direct from the battery.

If it’s got 4 headlights, the front end (and probably the harness) is off of a later year.

 

[shovelbill80]

What bulbs are in the high beams. Are there three wire for the low beam connectorsand two for high? What type of lamps?

 

[jbchevyfan]

Well here we are again. All wires from bulkhead to rear of truck show continuity. The part of the bulkhead mounted to the firewall, not the connector, has either started melting or the dielectric grease has turned black. It was very sticky to the touch with a meter probe. So I reconnected the bulkhead connector, tightened it down a little snug and just for fun installed my last 20 amp in the taillight fuse a slot to take some time to think. The fuse didn’t blow and the taillights work. But, now the left blinker stopped working. Everything is good from the headlight switch to the fuse box and the rear to the bulkhead clip. Am thinking the bulkhead is in such bad shape that it should either be replaced or bypassed. Any thoughts? Is there are replacement part available? Having a difficult time finding it online.

 

[shovelbill80]

Well here we are again. All wires from bulkhead to rear of truck show continuity. The part of the bulkhead mounted to the firewall, not the connector, has either started melting or the dielectric grease has turned black. It was very sticky to the touch with a meter probe. So I reconnected the bulkhead connector, tightened it down a little snug and just for fun installed my last 20 amp in the taillight fuse a slot to take some time to think. The fuse didn’t blow and the taillights work. But, now the left blinker stopped working. Everything is good from the headlight switch to the fuse box and the rear to the bulkhead clip. Am thinking the bulkhead is in such bad shape that it should either be replaced or bypassed. Any thoughts? Is there are replacement part available? Having a difficult time finding it online.

This?:

Bulkhead, Headlight Harness Bulkhead Connector Second Design (Bulkhead

Item pictures is the engine wiring harness bulkhead for 1975 - 1988 models. All wires have been removed and bulkhead cleaned of all sealants. These are sold individually. Item is used OEM that has been cleaned and any rust chemically removed. Item pictured might not be item shipped. Item...

newboyzsquarebodyrescue.com

 

[jbchevyfan]

I’ll try to post a pick. The shape doesn’t match the connector on this old truck.

 

[Matt69olds]

The black sticky tar is what the factory used to seal the bulkhead connector.

Does the left turn signal not work at all? Meaning does the indicator in the dash light up but not flash? What about either front or rear bulb?

Turn on the ignition, put the turn signal lever in the left turn position. Check for power on the yellow (left rear turn signal) and the light blue (left front turn signal) if you have power, the switch is good and the problem is more than likely under the hood. So the next move, check for power on the yellow and light blue at the front and rear harness connector. If you have power there, check the bulbs and sockets.