I did some diagnostic work on my '98 C5. My problem was the LH headlight wouldn't go up or down. The RH is fine. I recall some issues with delayed opening, finally it just wouldn't open. I recall when I washed the car the RH headlamp opened on it's own. After that the LH wouldn't open or close. I removed the headlamp connector at the LH capsule and applied 12V directly to the motor terminals, then reversed them. The door opened and closed with no problem. I removed the headlamp control module connectors and brought them into the engine compartment (barely reached). Check voltage and ground to the module, tested ok. Removed the control module and it smelt burnt. Cover on module was separating from from case. I pried it off and removed the circuit board. Definitely burnt components on the board. So my question is WHY? What caused this to happen. Was the cover already separating and when I washed the car the water damaged the components? I know there is power applied to the module all the time. Dealer want's over $300 for this part. I don't know what external issues may have caused this to fail. I'm just inquiring since I don't want to see the new module fail. Any comments are appreciated. I'll try to post a pic of the opened module.

Art

 

Art

They do fail!! Some just quit, some draw excessive current and kill the battery. I have NOT seen many failures. IMHO it was just the modules time to go. Purchasing a NEW module and making SURE that all the connections are clean and water tight and the pins in the connectors are not damaged, spread or corroded, everything should be fine.

Can you take some picture of the inside of that module and post them??

Thanks

Bill

 

It's been a few weeks since I replaced the module with a used one which works perfectly now. Here's a couple of pics of the circuit boarda and leaking housing. The housing pic is bad but the closest edge has separated from the housing allowing water inside. You can see where a component overheated. Probably due to water and shorting out.

Sorry it took so long.

 

WOW! What a POS part. That "circuit board" looks like something out of my late 70's High School electronics (you know, HIFI, 8 Track, reel-to-reel, CB radios) class. Nice job moving to the new millenium GM!

 

Other than improving the seal, how would you have designed the circuit board differently?

 

Actually, the module was designed in the old millennium

 

I would have used glass/epoxy board material and placed some heat sinking on the power devices. The power device on the right looks like it became too hot and burned out. From what I've read on this design, the module reads the motor current and turns the motor power off when the stops are hit instead of using limit switches.

 

....and those modifications won't help anything, if water is able to get inside the module.

 

I'm glad you posted this, I took the module out of my car as the headlights are being worked on and was surprised what it looked like. The back of the module is separated!

To seal the module they used that all purpose GM tar, notice the extra on the circuit board.

Since the module is attached at two corners, stress can pop the back cover off at the other corners.

The circuit board was burned a little as seen here.

I cleaned all the tar off the plastic housing. The rivets were drilled out of the two power devices and the green coating was cleaned off the copper in that area. Some scrap brass was soldered on the circuit board and a wire was soldered to that.

The other end of the wire (10 gage stranded) was connected to the power device with silver epoxy. This should provide more heat sinking than the little copper traces did. The 9 connector terminals were masked then both sides of the board were sprayed with clear paint for extra moisture protection.

Here's the parts to be assembled using Goop adhesive.

A little Goop was added around the two connectors before the circuit board was placed in the main housing then the trench around the board was filled with Goop and the back was snapped into place.

An aluminum plate was made and Gooped to the assembly, clamps are now holding all this together until the adhesive cures.

Tonight the module will be plugged back into the car to see if it still works. The Goop should keep the assembly together and dry, the aluminum plate should spread the stress over the whole back to keep the corners from popping out and the brass should keep the power devices cooler. I'm glad this was checked before it failed, who wants to spend $300 for another module sealed with tar.

 

Thanks for that info Fast One.

I'm having a problem with my module. It all started a few months ago when the LH headlight stopped working. I did all the checks and determined that it was the module.

I received a replacement from Corvette Central only to find a new fault - the headlights would close, but not open! Checked everything again, but it seemed to be the module. Sent it back for replacement.

In the meantime, I found a 'new' module for sale here in the UK. I installed that one and guess what... only the LH headlight operates!

I've stripped my old module and the new one. In the old one, the power transistor Q1 has burnt. In the new one, there are no signs of faults.

I'm guessing the IC is faulty, but I can't identify it. I've looked for equivalents, but can't find anything. The IC on the old module is labelled:

16511949
CS8931H

The new one is:

16512455
UEX00513

The number starting with 165XXXXX looks like a GM part number.

My question is, does anyone know what the IC is? In the electrical schematics, it's just shown as a solid state switch.

Cheers
David
Cornwall, England

 

I've got an extra with an intermit problem. When I get back from a coming trip, I'll open it up and see what's up with it.

 

Many thanks. I really appreciate any help on this one!
Cheers
David

 

It'll be about two weeks before I get back but if I can repair this, you can have it for free. Its got issues with the passenger headlamp not always coming up. I put one in that I bought off someone or ebay and its working just fine, so this extra has issues but I'll look into it. If you want it as-is, you can have it now but its up to you to repair it.

 

See how a single post can turn into a C5 MONEY SAVING idea!!

Thanks everyone who contributed and added pics and ideas!

Bill

 

Hi

I've been doing some checking... I opened the module I bought in the UK and discovered that it has an identical board inside to the one in jcgunn's & Fast One's pics.

On further investigation, it seems that although in identical outer cases, the internals are different between the C4 & C5 modules. This may explain why the C5 one doesn't work on my C4!

Many thanks for your kind offer, but I will have to see if I can get a specific C4 module. The seller of the C5 one I bought in the UK has agreed to take it back as he advertised it as C4.

Thanks again.

Cheers
David

 

That offer is also to the OP if he wishes.

 

The control module on the passenger recently started ticking. Does that mean it is gone or is about to go? As of now, my headlights go up, but will not go down unless I flick the High beams on.

 

If HID lights were added they can cause the problem of the motors not closing unless the high beams are selected, this is due to the reduced current draw of the more efficient HIDs. Most owners add power resistors to increase the current draw so the lights will open and close as they did with the old lamps. Did you remove the control module and check it for defects as seen in the above photos such as a warped cover that can let in water?

 

I've been running HIDs for three months with no issues. What is happening with the lights going down is a new issue.

 

It seems that most everyone buys these things used. I got the shock of my life when the dealer told me these modules cost $675.00 new.

The guy at the parts desk recommend finding a used one at the bone yard or Ebay. My unit is ticking. It is not getting warm. It's only making a ticking sound.