Headlight motor(?) goes tap-tap-tap
Thread Starter
Instructor
Joined: Jan 2000
Posts: 231
Likes: 46
From: San Antonio TX
Headlight motor(?) goes tap-tap-tap
My C5 has been sitting for several weeks and when I tried to start it yesterday there was no electrical power at all. No interior lights, no hatch release, no vanity mirror lights, nothing.
I hooked up my battery tender and let the battery charge overnight. This morning I heard a tap-tap-tap-tap sound coming from the front of the engine compartment, near the left headlight. That's when I remember last month I had turned on the headlights and the right side had raised up and on but the left side had stayed down. At the time, I just cycled the lights off and on again and both headlights came up and on correctly so I promptly forgot about the issue.
Figuring this is a headlight motor issue, I pulled engine compartment fuse #4 (left headlamp motor) and the tap-tap-tap immediately slowed to tap-----tap-----tap (half-speed?). I pulled fuse #3 (right headlamp motor) and the sound stopped completely. I'm going to leave the battery tender connected for 24 hours to see if the battery will reach a full charge with the fuses out.
I guess I should start troubleshooting by checking the grounds and connectors for the left and right headlights as well as the headlight control module.
My search found some threads about headlight problems, but not this exact issue. Has anyone experienced this issue and/or have pictures of the headlight control module?
TIA
I hooked up my battery tender and let the battery charge overnight. This morning I heard a tap-tap-tap-tap sound coming from the front of the engine compartment, near the left headlight. That's when I remember last month I had turned on the headlights and the right side had raised up and on but the left side had stayed down. At the time, I just cycled the lights off and on again and both headlights came up and on correctly so I promptly forgot about the issue.
Figuring this is a headlight motor issue, I pulled engine compartment fuse #4 (left headlamp motor) and the tap-tap-tap immediately slowed to tap-----tap-----tap (half-speed?). I pulled fuse #3 (right headlamp motor) and the sound stopped completely. I'm going to leave the battery tender connected for 24 hours to see if the battery will reach a full charge with the fuses out.
I guess I should start troubleshooting by checking the grounds and connectors for the left and right headlights as well as the headlight control module.
My search found some threads about headlight problems, but not this exact issue. Has anyone experienced this issue and/or have pictures of the headlight control module?
TIA
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
The headlight motors are controlled by the headlight motor CONTROL MODULE. The Headlight assy does NOT have any UP-DOWN limit switches.
It has PLASTIC STOPS that the arm contact when the light is fully raised or fully lowered. Take a very good look at those stops and see if any of them are cracked/broken or missing. You can purchase new ones and its important to have good stops.
The Control Module senses motor draw CURRENT and when the bucket arm contacts the stops, the motor/s draw/s high current and the control module senses the increase in current and STOPS driving the assembly.
If that module is bad, it can cause the motors to use too much current to keep the buckets UP or DOWN. The module is located under the passengers headlight. Feel it and see if it is HOT when the light buckets are not driving. Don't forget to reinstall your fuses. It may take a while for the module to heat up if its bad.
You can always do a C5 battery current draw test to see what current your car is drawing when the BCM goes into SLEEP/SECURITY MODE. Should be somewhere around 20 milliamps.
The module is sealed on the back with an epoxy. That epoxy can and does shrink and water/moisture can get inside the module and damage it.
It has PLASTIC STOPS that the arm contact when the light is fully raised or fully lowered. Take a very good look at those stops and see if any of them are cracked/broken or missing. You can purchase new ones and its important to have good stops.
The Control Module senses motor draw CURRENT and when the bucket arm contacts the stops, the motor/s draw/s high current and the control module senses the increase in current and STOPS driving the assembly.
If that module is bad, it can cause the motors to use too much current to keep the buckets UP or DOWN. The module is located under the passengers headlight. Feel it and see if it is HOT when the light buckets are not driving. Don't forget to reinstall your fuses. It may take a while for the module to heat up if its bad.
You can always do a C5 battery current draw test to see what current your car is drawing when the BCM goes into SLEEP/SECURITY MODE. Should be somewhere around 20 milliamps.
The module is sealed on the back with an epoxy. That epoxy can and does shrink and water/moisture can get inside the module and damage it.
Drifting
Joined: Mar 2013
Posts: 1,496
Likes: 355
From: Little Rock Arkansas
I think what you are describing is the typical "grind" or tap noise owners report when headlamp gears are damaged. You can test the electricals as mentioned above but I would disassemble the gear and ensure there's no physical issues. Any sounds heard with the headlamps opening or closing point to physical issues with either the plastic gear or (less likely) the worm drive damaged. It taps - or "grinds" - as the damaged gear teeth (typically on the plastic gear) contact the worm drive.
Below is an incredibly good step by step of removing the assembly and disassembling the headlight motor. It will take approximately an hour worth of work if you've never done it before:
https://www.corvetteforum.com/forums...orialized.html
Disassembling the motor will allow you to asses the physical condition of the interior components. I did not see what year C5 you have but there are two types of motors used on C5's. The later style has more plastic components and requires an extra step on reassembly.
You will probably have to purchase a new gear. Typically brass replacements are desired. Personally I recommend Rodney Dickman's replacements and you can also find them from a variety of CF vendors. Expect to pay $40-$50.
Another item you will want to do on reassembly (I don't think the step-by-step mentions this) is "flip" the nylon bumpers over (or purchase replacements). The bumpers - there are four to a headlight assembly - wear down over time and flipping them serves as a good temporary assistant to preventing premature wear on the motors. As the bumpers wear down, they stress the limits of the gear and worm drive.
EDITED:
Below is an incredibly good step by step of removing the assembly and disassembling the headlight motor. It will take approximately an hour worth of work if you've never done it before:
https://www.corvetteforum.com/forums...orialized.html
Disassembling the motor will allow you to asses the physical condition of the interior components. I did not see what year C5 you have but there are two types of motors used on C5's. The later style has more plastic components and requires an extra step on reassembly.
You will probably have to purchase a new gear. Typically brass replacements are desired. Personally I recommend Rodney Dickman's replacements and you can also find them from a variety of CF vendors. Expect to pay $40-$50.
Another item you will want to do on reassembly (I don't think the step-by-step mentions this) is "flip" the nylon bumpers over (or purchase replacements). The bumpers - there are four to a headlight assembly - wear down over time and flipping them serves as a good temporary assistant to preventing premature wear on the motors. As the bumpers wear down, they stress the limits of the gear and worm drive.
EDITED:
Last edited by Velocity_Vette; Dec 22, 2016 at 02:26 PM. Reason: posted late and removed emojis
