1981 GMC Sierra Headlight Issue

[81GMCSierra1500]

Hi all,

I have a 1981 GMC Sierra Classic, with the quad headlight front end, and I've just encountered an issue with my headlights. I'll pull the knob, and everything BUT my headlights will turn on... EXCEPT, when I have my high beams on, the top two headlights turn on to the regular low-beam setting. Just to clarify, when headlights are on W/O high beams, nothing is on, and when I turn the high beams on, the lower bank doesn't turn on, but the upper bank goes to it's "low" setting, and no "high beam" light comes on in the dash either... What's wrong!?!

[81GMCSierra1500]

I'm hoping it's just a pull knob issue, and not a major cost...

[Your41Plague12]

Probably a bad dimmer switch. Mine went bad in my '83 once, and it did something similar. It's cheap, so it's probably worth a shot.

[81GMCSierra1500]

Originally Posted by Your41Plague12

Probably a bad dimmer switch. Mine went bad in my '83 once, and it did something similar. It's cheap, so it's probably worth a shot.

Update. Went and bought a new dimmer switch, same issue is still happening... could it be my on-floor high beam?

[motornut]

Originally Posted by 81GMCSierra1500

Update. Went and bought a new dimmer switch, same issue is still happening... could it be my on-floor high beam?

you can try to jumper the floor headlight dimmer (not dash dimmer) for testing,those wires at the plug heat up some and can melt the plug,worth a peek down there

[Your41Plague12]

Originally Posted by 81GMCSierra1500

Update. Went and bought a new dimmer switch, same issue is still happening... could it be my on-floor high beam?

That's what I meant by dimmer switch. It's probably your "high beam switch" on the floor.

[81GMCSierra1500]

Originally Posted by Your41Plague12

That's what I meant by dimmer switch. It's probably your "high beam switch" on the floor.

That's what I thought it was... I will try that, as it was next on my list...

Cheers, guys!

'81

[Your41Plague12]

Let us know how it worked out. I'm pretty sure that's your problem, the same thing happened in my '83 and that was the culprit.

[81GMCSierra1500]

Will do as soon as I'm done with my Grad. Once that's finished, I'll have all summer!

[clinebarger]

The Delco-Remy floor mounted dimmer switches rarely goes actually bad, They get dirty, 10 to 20 quick stomps on it will fix it (Have the head lamps OFF during this!)

[81GMCSierra1500]

Originally Posted by clinebarger

The Delco-Remy floor mounted dimmer switches rarely goes actually bad, They get dirty, 10 to 20 quick stomps on it will fix it (Have the head lamps OFF during this!)

Tried this several times, same thing is happening. I'm thinking it's either the switch or the wiring/plug. I'll take a deeper look at it this weekend.

[81GMCSierra1500]

Originally Posted by 81GMCSierra1500

Tried this several times, same thing is happening. I'm thinking it's either the switch or the wiring/plug. I'll take a deeper look at it this weekend.

Okay, still having the same issue with the headlights, and I am starting to worry... I also, don't want to spend the money on the floor-switch, especially if there's the chance that isn't the issue, same story as when I replaced the main dimmer switch & pull knob... Any thoughts? I will spend the money if I have to, but yeah...

[81GMCSierra1500]

And adding to the predicament, I have no gauge lighting either... what's happening!?!

[larey]

Look at this thread "http://67-72chevytrucks.com/vboard/showthread.php?t=545416" and get your manuals first is what I would recommend as it normally shows you what to look for. For your year on page 977 of the repair manual it shows what to look at first and what to test with a multi-meter.

Second part did you have gauge lights before you changed the dimmer switch in the dash?

I looked and could not find a circuit breaker or relay for you set-up except inside your actual headlight switch, on page 1069 which has the schematic on it.

Hope this may help..

Larey

[81GMCSierra1500]

Originally Posted by larey

Look at this thread "http://67-72chevytrucks.com/vboard/showthread.php?t=545416" and get your manuals first is what I would recommend as it normally shows you what to look for. For your year on page 977 of the repair manual it shows what to look at first and what to test with a multi-meter.

Second part did you have gauge lights before you changed the dimmer switch in the dash?

I looked and could not find a circuit breaker or relay for you set-up except inside your actual headlight switch, on page 1069 which has the schematic on it.

Hope this may help..

Larey

Larey,

I did not have dash lights before the dimmer swap, nor did I afterwards, but I am thinking the "Gauges" fuse is blown, but it is obstructed by a white plug, which I can't remove, so I won't be able to tell how too get that out... Is there a chance that the headlights are tied into the gauge lighting? and the next thing I'll try to do with the headlights is the floor switch, and if that doesn't work, into the shop she goes!

[larey]

All the lights are tied into the headlight switch itself looking at the schematic. I would start there before you buy anything else.

[81GMCSierra1500]

Originally Posted by larey

All the lights are tied into the headlight switch itself looking at the schematic. I would start there before you buy anything else.

Yeah, I think I'm onto my answer through a different thread, I'm going to replace my main battery-to-frame ground wire, as there's almost nothing left of it. And I already replaced my main switch, and that was most likely a complete waste of money and time...

[c3006]

Check the two small black ground wires from your headlight sockets to the sheet metal also,those ground wires can cause havoc with the electric system.

[81GMCSierra1500]

Originally Posted by c3006

Check the two small black ground wires from your headlight sockets to the sheet metal also,those ground wires can cause havoc with the electric system.

Yeah, willdo, I just swapped my original battery-to-rad support wire, and that did nothing... I'm going to have to get a pro to look at the old 'gal

[Just call me Sean]

Did you check the dash ground yet?

[81GMCSierra1500]

Originally Posted by Just call me Sean

Did you check the dash ground yet?

Couldn't find it... Remind me of where it is again?

[Just call me Sean]

Left of the column. Will be easier to find if you pull out the duct that passes under the column.

[81GMCSierra1500]

Originally Posted by Just call me Sean

Left of the column. Will be easier to find if you pull out the duct that passes under the column.

I will work on that tomorrow for sure, I need to get this fixed! I appreciate the help, everyone, especially Sean

[TN_Farmboy]

Originally Posted by 81GMCSierra1500

I will work on that tomorrow for sure, I need to get this fixed! I appreciate the help, everyone, especially Sean

81GMC- Did you have any luck with this fix? I've also got a '81 Sierra Classic that is giving me the same issues. I've replaced the dimmer switch to no avail. Trying to get some ideas before throwing stuff at the wall to see what sticks.

Thanks!