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1995 GMC Van Headlights

Tiny
95VANDURA
  • MEMBER
  • 1995 GMC VAN
  • V8
  • 2WD
  • AUTOMATIC
  • 200,000 MILES
Headlights recently started flashing like a police car. Going from high beam to low and on/off. Seams to be getting worse. What module could be causing this?
Friday, February 12th, 2010 AT 7:55 PM

7 Replies

Tiny
BUDDYCRAIGG
  • MECHANIC
  • 2,262 POSTS
Does this still happen if you manually turn on the lights?
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Saturday, February 13th, 2010 AT 2:12 AM
Tiny
95VANDURA
  • MEMBER
  • 4 POSTS
It stops for a while but starts again.
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Monday, February 15th, 2010 AT 10:33 AM
Tiny
BUDDYCRAIGG
  • MECHANIC
  • 2,262 POSTS
I've had a chance to look at your schematics and I have a few questions.

Do you have 4 headlight bulbs (2 low and 2 high)
or
do you have 2 bulbs that have the low and high built in to them.

Is the problem on both sides of the van.

Is the light really changing from the high bulb to the low bulb or is it the same bulb but is getting brighter and dimmer?
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Monday, February 15th, 2010 AT 6:44 PM
Tiny
95VANDURA
  • MEMBER
  • 4 POSTS
I have 4 headlight bulbs (Two high, Two low). It appears to be only the low beams which alternate on and off opposite of each other.
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Monday, February 22nd, 2010 AT 10:02 PM
Tiny
BUDDYCRAIGG
  • MECHANIC
  • 2,262 POSTS
What you are describing does not appear to be possible with a stock headlight setup.

Do you have Daytime running lights?
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Monday, February 22nd, 2010 AT 10:49 PM
Tiny
95VANDURA
  • MEMBER
  • 4 POSTS
No, just the standard parking lights and headlights that you have to manually turn on.
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Tuesday, February 23rd, 2010 AT 8:29 PM
Tiny
BUDDYCRAIGG
  • MECHANIC
  • 2,262 POSTS
Then I have no explanation.

A single power wire comes out of the dimmer switch and then branches off to the left and the right.

There isn't anywhere for the power to be swapped back and forth.

Unless you have owned the van since it was new, I'm speculating that someone (possibly a highway construction worker) may have installed a flasher system.

I only have 2 suggestions for you.
1 with the engine off, and the lights on, watch for the lights to start flashing and listen for any clicking relays.
Also unplug one of the lights and see if the other side continues to go on and off.

2 start physically tracking the power wire with a test light.
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Tuesday, February 23rd, 2010 AT 10:44 PM

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