Not idling when head lights are on??

[gmcgirl1980]

So, I have a 1995 GMC Sierra that has an odd problem. The truck runs great until you turn on the headlights. It starts trying idle down and die but when you shut the headlights off its back to running great. It has a new battery, alternator, all the grounds have been cleaned, and has a new headlight switch. What am I missing here?? It's not throwing any codes either so I'm at a loss. Only other thing we did to it before all of this started was replace the exhaust which wouldn't have anything to do with the headlights. Any advice would be greatly appreciated! I'm just not sure where to go from here!

 

[98trck]

are the bulbs oem
does it happen with only the parking lights on
dis connect head lights at the bulbs

if it doesn't happen the problem is after the switch
if it does happens the problem is at the switch

 

[gmcgirl1980]

The parking lights and the headlights generate the same results. It runs rough, idles down and tries to die. So the following is a list of new parts...
Battery, alternator, headlight switch, ECM, plugs, cap and rotor, grounds, PCV valve and MAP sensor.
The truck now has entered limp mode in the trans and the airbag light iswitch staying on? This is become a nightmare. If we pull the gauge cluster fuse it seems to run better as well as when we pull the airbag fuse. I'm lost and thinking it may be some sort of a serious electrical issue.

 

[98trck]

have you replaced the headlight relay
when I had to replace mine on my '98
at auto zone
I checked the box wiring schematics to the schematics on the relay and they were different
the wrong relay was in the box
so make sure you have the correct relay installed

 

[gmcgirl1980]

We have since got her going by swapping out the entire headlight assembly and adding additional grounds. She runs great. Thanks for your help

 

[98trck]

thanks for the update
nice to have a happy ending...