Headlight issues

[nolv4ho]

So i bought an 87 GMC Suburban 2500. It's in really good shape over-all. My issue is that the headlights will come on fine for 10 minutes fine, but then will flash off and on and continue to do so. (on for a second, off for like 10 seconds) I just replaced the switch. Did not fix the issue, and while I was putting it back together, after I replaced the negative battery terminal the automatic door lock switches started immediately trying to lock and unlock( it does not move the locks, but theres something switching on and off). So now not only do i still have the headlight problem, I have an automatic door lock problem too. Any help is apprecitated.

 

[WP29P4A]

The first thing to check is always the grounds, easiest thing to check and correct before spending time trying to find a problem caused by bad or missing grounds.

 

[SirRobyn0]

Does it do it both on high and low? do the parking lights flash to? It could very well be a ground, but if it's just the headlights you might wanna think about the high / low changer as well.

 

[nolv4ho]

It is just the headlights, Low beam or high beam too, if those are on. Conversely fog lights, dash lights stay steady on.

 

[Radiohead]

From too much current draw, causing an automatic circuit breaker to cycle?

 

[nolv4ho]

That's what I had read, and that's why I replaced the switch. Im pretty sure everything is stock. Where are the ground locations at that I should check?

 

[WP29P4A]

That's what I had read, and that's why I replaced the switch. Im pretty sure everything is stock. Where are the ground locations at that I should check?

There should be a ground for the headlights on the radiator support, there is also a ground for the dash, on the kick panel above the e-brake. Are the headlights standard incandescent bulbs? Not LED bulbs?

 

[Originalthor]

Does it have a command start or security system hiding up in the dash there?

Kinda weird for it to be good for 10 minutes then start doing stuff and also your door lock system is totally separate from the headlights so first thing came to my mind was a old command start or keyless entry system or alarm making thing do funny things

 

[nolv4ho]

As for the locks, I don't see any evidence of a security system. The only aftermarket things are the trailer brake control, and the ****** cd stereo. If I remove the silver 30 amp fuse, the locks stop trying to switch. I replaced with new fuse. Still same issue. I can hear a clicking underneath the dash by the stereo, on about 5 second intervals. I also notice that the lock plunger moves slightly, however its not enough to lock or unlock. And if I manually try to flip the lock switch i get nothing on either door. Is there a relay under the dash I should try to replace?

 

[timbritton]

I had this problem show up this weekend on my 82 GMC. I checked the headlight sockets . I found a fair amount of corrosion on both sockets and headlight prongs. I cleaned all four light prongs and sockets made sure they were snugly making contact and fixed the problem.

 

[nolv4ho]

Headlights are FIXED. After spending hours checking grounds and voltages, adding dialectric grease, and having 2 other people look at it, I went and bought another Headlight Switch from NAPA. I think the brand is Echlin. Plugged it in and Voila, issue fixed. So Beware of OEM Brand from Cost Less Auto Parts. Not to be confused with OEM (Original Equipment Manufacturer), which is a separate discussion.
Side Note: The old headlight switch I pulled out looked brand new, so I think the seller tried fixing it, and put a faulty one in too. Shady mfer. So that's 2, faulty switches in a row.

Now I just have to fix the door issue that randomly popped up in this journey.

 

[gmbellew]

there is a relay for the power locks. seems that maybe it has gone bad.

 

[mshawn]

G

It is just the headlights, Low beam or high beam too, if those are on. Conversely fog lights, dash lights stay steady on.

Factory fog lights?

 

[Wolverine]

Headlights are FIXED. After spending hours checking grounds and voltages, adding dialectric grease, and having 2 other people look at it, I went and bought another Headlight Switch from NAPA. I think the brand is Echlin. Plugged it in and Voila, issue fixed. So Beware of OEM Brand from Cost Less Auto Parts. Not to be confused with OEM (Original Equipment Manufacturer), which is a separate discussion.
Side Note: The old headlight switch I pulled out looked brand new, so I think the seller tried fixing it, and put a faulty one in too. Shady mfer. So that's 2, faulty switches in a row.

Now I just have to fix the door issue that randomly popped up in this journey.

I just bought and installed a new headlight switch that turned out faulty. It is increasingly difficult to purchase legit replacement parts, I would rather pay more than to have to do the job over...

 

[ReefkoiC10]

Reminds me of when one of the coils went bad on my LS, everyone says they hardly ever go bad must be a handful of other things wrong, but alas with electrical it could be anything really!