Question on my 69 headlights

**Edward D.** · September 17, 2020, 06:16 PM

Re: Question on my 69 headlights

Had this same winking headlight problem last year on a customers 69. Turned out the vacuum reservoir tank (tucked into drivers side fender) was leaking at the seams. Also, repro control valve was crap, dogbone inside leaked. NOS GM valve and a good used tank fixed the problem. Used tank was actually less expensive than solder fix of original so we went that way.

**Terry M.** · September 17, 2020, 10:04 PM

Re: Question on my 69 headlights

Originally posted by Michael Leonard (46610)

Guys,

On my 69 L46 4-spd non-A/C car I have spent some time troubleshooting the headlights and wsw door vacuum systems. I have gotten them to a point where they are working perfectly. I have also been able to confirm that the entire system has no major vacuum leak by applying my vacuum pump and then observing the pressure gauge after I turn the pump off and I have been able to confirm that it holds pressure for quite a long time.

My question is when I first start up the car the headlights pop-up and then slowly go down over the next 1-2 minutes. What could be causing this if there is no vacuum leak? Not sure it matters but I did put a modest cam in the car when I rebuilt the engine but maybe it affects the rate that the engine builds vacuum?

What's interesting is that this doesn't happen if I connect and turn on my vacuum pump, which I think might build vacuum more quickly maybe? Curious to hear your thoughts. Thanks for your assistance.

Mike

The vacuum system is designed so the vacuum "builds" in the control circuit first.

Control circuit, the smaller tubes, has less volume than the power circuit (large tubes). As vacuum "builds" it should "build" in the smaller control circuit first -- unless there is a leak in that circuit. That leak can be in one of the valves or the hoses or the connection(s) between them. Try checking the control valve(s) between the front headlights. Even if it/they are new; they can leak. Maybe even especially if they are new.

In Ed's case the vacuum didn't "build" fast enough to get the control system evacuated first due to the leak in the vacuum tank; and that is certainly worth considering and testing for. I pray you don't have power brakes. Removing the vacuum tank on a power brake car is a gold plated PITA.

**Michael L.** · September 18, 2020, 09:34 AM

**Bob D.** · September 18, 2020, 09:47 AM

Re: Question on my 69 headlights

Mike

Check the relay valves in the nose to make sure one of them has not started leaking. If it has send back and I can repair. Sometimes if contamination gets into the valve it will cause the seal to leak on the plunger and that will cause the problem. The filter on the bottom of the valve only stops the big pieces of grrit.

Bob

**Michael L.** · September 18, 2020, 01:31 PM

Re: Question on my 69 headlights

Thanks Bob. I checked the valve and it's good. No leak. I then checked the proximal (small white striped control hose) and there was a proximal leak. I traced it back to the vacuum override switch under the dash. I had checked it previously during my troubleshooting and it seemed to hold vacuum but it's clearly leaking now. Can these be rebuilt or do I need to just order a new one?

Correction: I just did a closer inspection of the override switch and it actually is not leaking. The leak is coming from the factory coupler I re-used to connect the vacuum hoses to the switch. See the attached pic. This was leaking earlier during my troubleshooting but I used sealant on the connections (both the hose to the brass connectors and the coupler to the switch) and thought I had solved it but the coupler is still leaking. I have not seen these in my catalogs from the vendors, does anyone sell these?

Mike

IMG_4711.jpg

**Bob D.** · September 18, 2020, 02:24 PM

Re: Question on my 69 headlights

I have not seen these in reproduction. Not sure they could be rebuilt. You may want to try David Sokolowski to see if he has any.

**Michael L.** · September 18, 2020, 10:02 PM

Re: Question on my 69 headlights

This car has me totally befuddled. After discovering the leaking coupler and removing it I reconnected the vacuum lines directly to the override switch and started the car and the headlights popped up again. I carefully checked the lines coming and going from the override switch, both the blue stripe Coming from the HL switch and the white stripe to the HL control valve and there is no vacuum leak anywhere in the system. What could I be missing?

Mike

**Michael L.** · September 25, 2020, 02:07 PM

Re: Question on my 69 headlights

Once again this car has befuddled me. I thought I had discovered the problem when I realized the coupler was leaking. So I removed it and attached the hoses directly to the bypass switch thinking I have solved the problem but when I started the car the headlights popped up. Again, when I use my mighty vac on the control valve by the headlights there is no leak and checking both sides of the bypass switch shows no leaks either, meaning the headlight switch isn't leaking. What am I missing?

**Charles H.** · September 25, 2020, 08:24 PM

Re: Question on my 69 headlights

I worked at a Chevrolet dealer in the Boston area when these cars were new. Winking headlights upon startup were always caused by a bad check valve. It's a round aluminum 3 port valve located just off the intake manifold behind the carburetor. Paragon# 2343. Try it-it's cheap.

**Tom M.** · September 26, 2020, 07:11 AM

Re: Question on my 69 headlights

I had the WS wiper door opening on shutdown and it was a problem check valve. Test it and let us know what you find.

Question on my 69 headlights

Question on my 69 headlights

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