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Discussion Starter · #1 ·
Hi all,
My 1998 corvette headlights will not close. I have checked the fuses 8,9 and 10. No luck. This morning I noticed that I also don’t have dash lights. But cruise control still works.I cleaned the 2 grounds and replaced the 3 fuses. Where should I check next?
 

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DC PIT CREW BOSS
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Are you getting any codes?
 
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The headlamp control module mounts under the passenger side headlight. With the headlights open you should unplug the motor from the vehicle so it can not close on you. Then remove the plastic bezel from the open RH headlamp assembly and you will be able to see and reach down below the headlamp to the control module. It is a small black plastic piece with 2 plugs going to it. This is the relay that sends power to the motors and sends reverse polarity to close. This is likely your failure. Don't forget to inspect the 2 connectors for water intrusion or expanded pins.

Of the wires running to these 2 connectors..

Black is ground. It needs to be grounded at all times

Orange is power There are 2 of these wires that run to seperate fuses in the underhood fuse block and get power all the time

White is the headlamp on signal This should get power only when the headlamps are commanded on

Dark Green is the headlamp off signal This should get power only when the headlight switch is in the off position

Those wires are all in connector C1 and connector C2 has the pair of green wires and the pair of blue wires that go to each headlamp motor. If you are having a problem getting power to the white or green wires when the headlamp switch is in a given state then you obviously have a headlamp switch or BCM/ambient light sensor failure as the BCM can command the headlights on and off with the Twilight Sentinel. If when the headlamps are switched off you have no power on the white wire and power on the dk green wire and power on both orange wires and ground on the black wire then you likely have a failed headlamp control module.

One final test you can perform is to use the knob on each headlight motor to manually run each motor down to the half way position and then retest the operation. There are switches in the motors that break contacts when the motor hits it's point of load/stop and while both failing together would be rather rare, this is an important verification step if we want to make sure we look smart and ensure that we only replace one part to correct the failure.
 

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Discussion Starter · #4 ·
The headlamp control module mounts under the passenger side headlight. With the headlights open you should unplug the motor from the vehicle so it can not close on you. Then remove the plastic bezel from the open RH headlamp assembly and you will be able to see and reach down below the headlamp to the control module. It is a small black plastic piece with 2 plugs going to it. This is the relay that sends power to the motors and sends reverse polarity to close. This is likely your failure. Don't forget to inspect the 2 connectors for water intrusion or expanded pins.

Of the wires running to these 2 connectors..

Black is ground. It needs to be grounded at all times

Orange is power There are 2 of these wires that run to seperate fuses in the underhood fuse block and get power all the time

White is the headlamp on signal This should get power only when the headlamps are commanded on

Dark Green is the headlamp off signal This should get power only when the headlight switch is in the off position

Those wires are all in connector C1 and connector C2 has the pair of green wires and the pair of blue wires that go to each headlamp motor. If you are having a problem getting power to the white or green wires when the headlamp switch is in a given state then you obviously have a headlamp switch or BCM/ambient light sensor failure as the BCM can command the headlights on and off with the Twilight Sentinel. If when the headlamps are switched off you have no power on the white wire and power on the dk green wire and power on both orange wires and ground on the black wire then you likely have a failed headlamp control module.

One final test you can perform is to use the knob on each headlight motor to manually run each motor down to the half way position and then retest the operation. There are switches in the motors that break contacts when the motor hits it's point of load/stop and while both failing together would be rather rare, this is an important verification step if we want to make sure we look smart and ensure that we only replace one part to correct the failure.
Thanks for the info. I will troubleshoot and let everyone know the out come
 

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Something like this happened on my 2000 vet. I would look at the light switch. This was a common problem with this switch on many GM vehicles. A replacement switch runs about $125 on Amazon and takes about 40 minutes to change yourself. Now I took the switch out and took it apart. The problem is 2 of the copper contact in the switch was not position right and after moving back and forth for a few years just stopped making contact. I my case it took out the dash and rear lights. I just bent the copper back and it has been fine now for 12 years. I found the instructions to remove the switch and fix it on the Corvette Forum. C5 Corvettes, 1997 - 2004 - CorvetteForum - Chevrolet Corvette Forum Discussion
 

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Discussion Starter · #7 ·
I replaced my headlight module and that was the problem. Fixed it goes up and down. But now I do not have running lights. Turn signal lights work. Lights go up and down. Should I replace the switch it’s self. Or is there a fuse that I missed?
thanks for all the troubleshooting advice it worked on the module.
Boatman
 

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I replaced my headlight module and that was the problem. Fixed it goes up and down. But now I do not have running lights. Turn signal lights work. Lights go up and down. Should I replace the switch it’s self. Or is there a fuse that I missed?
thanks for all the troubleshooting advice it worked on the module.
Boatman
On the passenger toe board in that fuse block fuse #6 is labeled 'PKT/LP' and it is a 10a little red fuse.
 
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