Why are the headlights up ?
Thread Starter
Cruising
Joined: Dec 2023
Posts: 10
Likes: 2
From: Australia
Why are the headlights up ?
Why do the headlights come up on my '98 when I switch the park lamps on ? The lights come up but the headlights don't actually illuminate. They stay up and Illuminate if I switch to headlights. I've read in the manual that you can keep the headlights up (and extinguished) by switching them on and then back to park lamp position. What am I doing wrong ?
Thread Starter
Cruising
Joined: Dec 2023
Posts: 10
Likes: 2
From: Australia
Hi Tony, thanks for your suggestion. Probably not viable to ship the part you mention back to the USA from Australia. Looking back now at what happened immediately prior to discovering the issue, I had just reconnected the under hood emergency light that the previous owner had disconnected, (it’s now working) and secured the main headlight connector cluster back onto the little clip on the inner fender. Looking at your wiring diagram and wondering if Headlamp Door Control Module might have a bad ground ? I guess it’s going to be a process of elimination to find the fault.
Former Vendor
Joined: May 2022
Posts: 128
Likes: 17
From: Texas
Ah yes, that’s a bit of a trip! You can check for 12vdc on terminal A on the connector for the headlight door control module with parking lights on. If you have voltage, I’d assume an issue with your headlight switch. If no voltage, definitely a control module failure.
Off sends 12v to close the doors, On sends 12v to open the doors. Parking lights on is a dead band for the doors with no movement.
Off sends 12v to close the doors, On sends 12v to open the doors. Parking lights on is a dead band for the doors with no movement.
Advanced
Joined: Aug 2018
Posts: 80
Likes: 7
From: San Diego County, CA
St. Jude Donor '21
Do your headlights make the grinding noise when you turn your headlights off? If so, maybe that's your problem. If I'm remembering correctly, when one of my headlight gears was worn out and grinding at the down position, when i would turn on my parking lights the headlights would go up with the headlights off.
Thread Starter
Cruising
Joined: Dec 2023
Posts: 10
Likes: 2
From: Australia
Thanks Big Mike - yes that's exactly what has happened. Headlamp has shredded the drive gear and then gone into "up mode" when I turn the park lamps on. I'm waiting on drive gear to arrive so I can fit that, and then we'll see if the problem persists ? good call mate thanks for your input.
Thread Starter
Cruising
Joined: Dec 2023
Posts: 10
Likes: 2
From: Australia
Crisis averted ! Fitted new headlight drive gear today, thanks YouTube for the tutorials. Happy to report everything is back to normal. It’s a pretty straight forward job, and interesting to observe how GM engineer these components. Lots of plastic parts that are only going to get brittle over time, clearly the C5 was designed and constructed on a tight budget. Very different to my ‘73 but I guess that’s what 25 years of automotive advancement did to the industry. Thanks for your input guys, on to the next project, updating the front park lamp assembly.
