Topic: Headlight issue?
in Forum: C4 Electrical
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On my 92 if I'm running my parking lights and I turn them off I hear a light thumping sound towards the front of the car for a few seconds. Any ideas? Thx 

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Spring Hill, FL - USA
Joined: 8/9/2010
Posts: 59
Vette(s): 1992 coupe.
Custom.
Is there a rabbit, stuck in the area, that is afraid of the dark?
darn noises. Turn up the radio or get loud pipes.
What is connected to the same circut?
W/W pump?
Anti lock system?
What else could make a thump sound?
Have no idea, my radio is too loud.
Leaking vacuum port/filter?
Look for a cracked hose, near the cruise control area.
Pulsing noise has to be constant.
Could be your head light motor, getting cross feed from the parking light wiring.
Keep us post on the results. Never know when some one else will have the same problem.

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lanoka harbor, NJ - USA
Joined: 3/22/2009
Posts: 1363
Vette(s): 1990 L-98 white/ red/black leather interior targa top auto
1975 L48 blue/black leather interior t tops auto
best thing to do jed would be to have someone else turn the lights on and off and open the hood and see if you can pinpoint where the clicking is coming from. the control box for the headlights opening and closing is in the front left wheel well. could be as suggested a cross feed. let us know.
the dynamic duo

c3vr life member #97
I have been dealing with 80's Firebirds and Corvettes for a while now. When the headlight circuit gets an "off" signal the down relay clicks in... This is a normal sound from 0 miles, straight from the factory. If you'll notice when you hook or unhood the battery you get the same thing.
Parking lights only or headlights?
jimmymack 2011-05-18 14:34:51
If it is happening with the headlight, my guess is it's the headlight motor accuator thingy (pretty technical, huh?). There is one in back of each light, knob on top. It governs the motor speed and if you replace your headlights you have to play with it to swing them up to remove the headlight cowl screws. When I did mine, I had to adjust one side to match the other and it made the thumping sound you describe. Get someone to turn headlights off and on and just adjust it until you get it right.
If it's parking lights only , sounds like you got good advice above.
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Orange Park, FL - USA
Joined: 12/4/2009
Posts: 56
Vette(s): 1996 LT4 Blk/Blk coupe all origional
I had the same problem with my '96 LT4. When you turn on or off the fog lights the headlight motors wouls run for a few seconds. Also when turning on the headlights the motors would run on for a few seconds and made a sound of light thumping until it stopped. The cure I found (right headlight didn't open all the way) was to remove headlight assemblies and take the motors apart. Be sure to inscribe light lines on the brackets so they can be replaced with the correct position. There are only four bolts holding the brackets in place. Before removing you will have to turn the hand knob until the headlight is half open and expose the two philips screws on each side of the the covers. One on each side and two bolts on the inside and remove the covers. Then the four bolts to remove the assembly. Now the noise is caused by worn out bearings in the motors. The factory manual procedure is to replace the motors at about $400 each. The origional bearings are made of some sort of compressed grease. These dry out and turn to dust. The motors (now on the kitchen table) have a round section and these hold the bearings. Any of the aftermarket catalogs list replacement Delron bearings for around $1/ea. Take the motors apart and open the bearing area. It will be full of dust from the broken down grease bearings. Clean out the residue and insert three delron bearings in each motor. I coated mine with a light coat of grease. LIGHT COAT. Then reasemble the motors and reinstall. The right one is a little more diifficult because of the location of the pins holding the rotary arms. It took me about 3hrs for the whole job. My headlights now snap open and closed with no run on and when I turn on only the fog lights there is no sound. It's not as complicated as it sounds. I pulled my assemblies again recently to install Hella lights. Used the same scribe marks an everything fit fine. I did that over a year ago and its as close to a permanent fix as you can get. The Delron bearings should last for many years.
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lanoka harbor, NJ - USA
Joined: 3/22/2009
Posts: 1363
Vette(s): 1990 L-98 white/ red/black leather interior targa top auto
1975 L48 blue/black leather interior t tops auto
they are also making bronze gears for the motors instead of the plastic ones.may want to consider installing them too.
the dynamic duo

c3vr life member #97
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Orange Park, FL - USA
Joined: 12/4/2009
Posts: 56
Vette(s): 1996 LT4 Blk/Blk coupe all origional
True bronze gears are available but are relativly expensive. After cleaning my plastic gears showed no wear after 15yrs and 60,000mi. The glass lens Hella lamps are about twice the weight of the origional headlights so in another 10yrs or so I may make the investment in time and money to change them.
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lanoka harbor, NJ - USA
Joined: 3/22/2009
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Vette(s): 1990 L-98 white/ red/black leather interior targa top auto
1975 L48 blue/black leather interior t tops auto
this is one of the improvements you make if you can afford it. only way i would even consider it was if my gears were worn.
the dynamic duo

c3vr life member #97
in Forum: C4 Electrical
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