79 headlight switch vacuum leak?

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Burnt_Orange79

Burnt_Orange79

Active member
Joined
Mar 13, 2011
Messages
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Location
Bourbonnais, IL
The headlight doors on our 79 Bird only stay closed for about 30 seconds after the car is turned off. Is it possible that the headlight switch could be causing a vacuum leak? Today I replaced the headlight switch with an extra switch that I had that came in a box of spare parts when I bought the car. The headlight doors only stayed closed for about a minute with that switch installed. I did hear the hissing sound of a vacuum leak, but all of the vacuum lines seem to be in good condition. Any ideas?
 
can you locate the source of the hissing? I've had my bird for about a month and have had no trouble with the headlight doors so I dont think I can be much help here. there is a manual valve on the drivers side fender, make sure that it is completely turned to where the vacuum lines are facing each other. again not sure if this is your problem but could be.
 
Both of my birds covers only stay closed a couple minutes. Just thought the pump or whatever was old. Stays closed with the engine running so I'm not too bothered by it.
 
Headlight Covers, Vaccum Leak, Steps to take

The problem of the eyelids opening up too soon is a common problem with our Birds.
The eyelids should stay closed for a week or so. If not, there are some fixes that most guys can deal with effectively--if you're patient.
In order of priority here are the sources of the problem:

1) Leaky headlight switch (located under the dash). Even new NOS switches leak due to sitting on the shelf for 30 years. Place your head under the dash (motor off) and listen for a subtle hiss. The hiss may be imperceptible. Make sure the three vacuum hoses are fitted securely to the switch itself.

2) Leaky check valve: small aluminum valve (three hose connections) located on the driver-side fender skirt.

3) Poor connection of vacuum line to the vacuum port on the back-side of the intake manifold. Remove your air cleaner. Use a strong light to inspect the connection. Cut off a bit of the hose and re-plug it in to the port.

4) Vaccum air tank: the tank where the vacuum is stored (to keep the headlight covers closed) is located under the front-portion of the driver-side fender (out of sight). You access it by removing the radiator overflow tank and the two horns. Notice the vacuum line plugged into the side of the tank. Check for a leaky connection there. Cut off some of the line and re-plug it in. The tank may have developed a leak as well.

5) Removing the tank: Remove the three bolts that hold it in place. Two underneath, and one on the fender jam. It will take some jostling to remove the tank. Take the tank to a radiator shop and ask them to check for air leaks. They should be able to re-seal the tank.

6. Check for cracked hoses. The vacuum lines may have developed cracks. Inspect all hoses under bright lights. Replace as needed.

Hope this helps. Best wishes. Tim
 
The hissing sound seems to be coming from the drivers' side, near the firewall. If I get a chance later this afternoon, I will pull the car into the garage and follow the 6 steps listed below. Hopefully I will be able to pinpoint where the problem is coming from.
 
Ok, I checked everything over on the car and I'm thinking that it has to be either the headlight switch or the small aluminum check valve. The hissing sound seems to be coming from near the aluminum check valve, but it may be coming from the switch because you can hear the hissing sound underneath the dash after shutting the car off. All of the vacuum lines are securely connected, and in good condition. The vacuum air tank in the fenderwell appears to be in very good connection, too.
 
Hissing sound

From your description of the location of the hiss, sounds like the culprit is the switch: a leak has developed. Not surprising after 30+ years. 79 switches are a little different than the 77-78 Bird switches. You might even be able to purchase a remanufactured unitfrom a local auto parts store. Check with NAPA, etc. Keep us posted as to your progress. Tim
 
My wife called all of the local parts stores, and even the Ford dealer yesterday- nobody has a switch or can get one. I guess I will have to watch Ebay and see if one turns up there. Thanks for letting me know that the 77-78 switches are different from the 79s, I wouldn't want to order something and have it not work.
John
 
Headlight Switch for 1979 Thunderbird

John:

Phone Green Sales at 1-800-543-4959 and see if they have a unit for you.
Here's the part number for the 79 Bird: Motorcraft, D9SB
11654-AB.

If they don't have it try Miller Obsolete: 1-800-546-7278

Keep me posted. Tim
 
I talked to Green Sales today, and it turns out that there were two different switches offered in '79-one for cars with the visibility group, one for cars without. Part no. D9SB-11654-AB is for cars with the visibility group. I'll have to take the switch back out of our car to check the part no. to see which switch I need. I'm pretty sure that our car doesn't have the visibility group because it is a pretty basic car with few options. Unfortunately the temps here are going to be back down in the 30s for the next several days, so it may be a little while before I'm able to work on the car again.
 
Headlight Switch

The only real difference in the two switches is an additional plug on the visibility group switch. Either will work for your Bird. They are shaped the same, both have three vacuum ports, etc. But if you have time to be precise, go for it. No problem. Keep me posted. Tim
 
Removing the headlight switch

Forgot to ask if you have removed the headlight switch before. Don't hesitate to ask if you need help. Tim
 
Tim Cole said:
Forgot to ask if you have removed the headlight switch before. Don't hesitate to ask if you need help. Tim
Click to expand...

Tim,
Yes, I actually removed the switch last weekend. It wasn't too bad of a job, but unfortunately I broke the end off of the switch bezel. Luckily, my wife was able to super glue it back together.
Based on the info in your previous post, I know our car doesn't have the visibilty group because there are no additional plugs on the switch. That saves me the hassle of having to take the switch back off. I'll go ahead and have my wife order a non-visibility group switch on Monday.
Thanks again for all of the help.
-John
 
Headlight switch

Sounds good. Not bad having your wife actually get involved to help with the repairs. I changed out both fuel filters today and my wife didn't even offer to help. But she did cook a great dinner and supper--so maybe I'll stick with the T-Bird and she th cuisine. Deal
 
Visibility Group

Graham:

The visibility group is another name for the "Light Group." dual beal lamp light, light under the hood, trunk, instrument panel, ashtray, glove box; door ajar warning lights and warning buzzer for "headslights on." Tim
 
Tim Cole said:
Sounds good. Not bad having your wife actually get involved to help with the repairs. I changed out both fuel filters today and my wife didn't even offer to help. But she did cook a great dinner and supper--so maybe I'll stick with the T-Bird and she th cuisine. Deal
Click to expand...

Yeah, it is nice that my wife takes an interest in helping to work on the Bird(especially since it's technically her car). I came home one day last week and she was outside washing it. We have 4 vehicles, and the upkeep on them takes a lot of time, so it's always nice to have a little bit of help. It looks like I'm going to have to wait a month or so before ordering the headlight switch because the registration and car insurance bills on 2 of our vehicles are all due this month. It's always rough when those bills all hit at the same time!
 
Headlight Switch on e-bay

If anyone is looking for a replacement or simply for an extra unit for their headlight switch, there is one for sale on e-bay currently: Item # 120704617758.

I am not familiar with this particular seller of NOS items. I am familiar with the Dennis Carpenter NOS parts and can vouch for them from experience over the years.

Jump on it if you like. They sold new back in the day for around $55.00.
Tim
 
Tim Cole said:
If anyone is looking for a replacement or simply for an extra unit for their headlight switch, there is one for sale on e-bay currently: Item # 120704617758.

I am not familiar with this particular seller of NOS items. I am familiar with the Dennis Carpenter NOS parts and can vouch for them from experience over the years.

Jump on it if you like. They sold new back in the day for around $55.00.
Tim
Click to expand...

Tim,
I saw that switch on ebay. I'm not sure if I can trust the seller, though, because the item description say it's a new NOS part but there looks to be some wear on it in the pics. I think I'll go ahead and spend the $75 to buy one from Green Sales. That's not a bad price if they sold new for $55.
-John
 

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