Headlight switch 72
When you turn the lights on does the switch open the vacuum or shut it off? I had my dash apart to fix the speedo and now my headlight doors won't raise. I hear a leak sound like at the switch. The hoses are on good. They worked fine before.
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Re: Headlight switch 72
Keith, is it possible that one of the hoses fell off the nipple when re-assembling? I had this happen one time with a result similar to yours.Don Lowe
NCRS #44382
Carolinas Chapter -
Re: Headlight switch 72
Keith
When you pull the headlight switch out you are bleeding control vacuum off at the relay thus change porting of the muscle air to raise the headlight buckets. To close is the reverse you apply control vacuum to the relay to lower the buckets.Comment
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Re: Headlight switch 72
Where's the relay? I had a trouble shooting book but can't find it. My AIM is at my shop.Comment
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Re: Headlight switch 72
There ought to be an illustration nearby in the AIM. The relays (there are two, one for each headlight actuator, in 1972) are centered on the car between the headlamps. Look up through the air opening behind the grilles and in front of the "spoiler." That is a lot easier to do with the car on a lift. If you really bend over with the hood open to look at the center of the opening in front of the hood, in front of the horn -- bingo. Bending over that far makes some people dizzy, so be cautious for your safety and that of your car.
Since you were working behind the dash, and you hear vacuum sucking there -- that is where I would concentrate my attention before creating chaos elsewhere. If something doesn't work right my experience tells me to check first at the last place I worked.TerryComment
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Re: Headlight switch 72
The trouble you are describing sounds like you may have pinched vacuum hose in the dash where you were working. Like Terry said check there first.Comment
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Re: Headlight switch 72
Yes I believe the problem is behind the dash. I was just trying to understand what takes place when I pull the switch. Everything is hooked up as best I can tell like in the AIM. If I unhook the two hoses to the headlight switch and connect them to each other should the headlights open? I am trying to see if the switch has a problem from me having the dash out. I only hear vacuum when I pull the switch. The doors open if I pull the bypass knob below the dash.Comment
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Re: Headlight switch 72
Keith
If your override works the headlamps then your problem is at or around the headlight switch and hoses.Comment
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Re: Headlight switch 72
Keith,
I do not know if you got this fixed or not. In answer to your original question, with everything set up correct, vacuum air holds the headlight doors closed. When you pull the headlight on, the vacuum holding the headlights closed is released to atmosphere. At the same time vacuum is applied to the two headlight relays, pulling the internal plunger and applying vacuum to the opposite side of the actuator opening the headlights.
Truth is, the vacuum at the plunger is what is actually holding the lights closed along with spring tension. When the switch is turned on it just releases the air on the vacuum side of the relay. This allows a different vacuum source to move the plunger. That vacuum is always on the plunger.
I can send you a really clear and easy diagram if you need it. At this point it sounds to me like the two hoses on your light switch are reversed.
The easiest way to tell if they are reversed is if you pull the light switch on and you hear a vacuum, but do not when it is off, your two lines are reversed.
Also, if your override opens the doors, but does not close them again, the two hoses on your light switch are reversed. EDIT; They will close again if the headlight switch is off. They will stay open if the headlight switch is left on.
If by chance the override does close the lights again, let me know. I have some more thinking to do.
The system is very simple, but like a lot of things, until you have a diagram or someone to show you, it can be a little intimidating.
Hang in thereand have fun with it.Comment
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Re: Headlight switch 72
Monte, that sounds exactly like what it is doing. I put the hoses on the switch like it appeared in the AIM but it seamed reversed from how it was before. I should have taken a pic but will reverse them and see. A better diagram would be nice though.Comment
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Re: Headlight switch 72
Keith
One has to remember there are 2 engine vacuum circuits and 1 electrical in the headlight door and wiper door systems.
1. Small hoses are for the control side of this operation.
2. Larger hoses the muscle side of the system.
3. Also small hose feeds the heating/AC and Astro ventilation system.
4. The electric side only deals with the wiper door.
The small hoses are for control the vacuum comes from the check valve then to the control switches whether it is the system switch or the override switch.
Control to close a system vacuum is sent to the relay valves small hose on the top this causes the porting for muscle vacuum to the closed side of the actuators.
To open a system the vacuum is bleed off the relay valve this allow a spring in the relay to shuttle or change porting to the actuator open side causing the item to open.
Muscle vacuum are the large hoses that comes off the check valve then to the reservoir tank and then to the lower sections of the vacuum relays for porting to the actuators.
In the wiper door system there is a electrical/vacuum solenoid behind the Tach. it is electrically controlled by the wiper switch porting vacuum to or off the relay valve to operate the door. You also have a override switch for manual operation.
The system is a fail-safe design that if you have a total loss of vacuum it will allow you to raise the headlights or wiper door manually.Comment
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Re: Headlight switch 72
Keith,
I know I already sent you this, but I thought a few others might be able to use it as well. I will send the wiper diagram to your regular e-mail. It has the electrical as well.
Feels like it is heading off in a new direction.
Comment
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Re: Headlight switch 72
Thanks guys. monte was right on about the Jose's reversed at the switch. For anybody searching in the future the AIM is backwards. Now you got me thinking about the wiper door. It has never opened since I have had the car. If I pull the bypass it doesn't open but I can pull it up and it will stay up and close when I push the bypass up. I started checking on this a couple years ago and realized some of the wires have been replaced. So I was just living with it. The biggest problem is if I turn the wipers on with the switch they try to come up with the door down. It's like the switch that is supposed to prevent this is bypassed. So I have two issues. 1door doesn't open. 2. Wipers try to run with door closed.Comment
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Re: Headlight switch 72
I would love to suggest you start a separate thread about the wipers so that someone searching in the future stands a better chance of finding answers.
On the firewall (BTW that is not the correct term, but everyone understands it) just to the passenger side of the wiper motor & washer pump is a rod that comes out of the chamber that the wipers park in. That rod presses on a switch with a button in the middle and two large red wires (one on each end IIRC). When the wiper door is up that button on that switch is released and power flows through that switch (on the two red wires) to the wiper motor. If the wiper door is down the button is pressed in and NO power flows through that switch and there is no power to the wiper motor and the wipers don't work.
If your wipers try to work with the door down the problem is (in no particular order):
1) the linkage to that button is not properly adjusted (or parts of the linkage are missing or bent)
2) the switch is malfunctioning and is closed all the time
3) someone has modified the wires by-passing the switch.
All three of those possibilities are either readily visible or easily tested with an electrical light probe or a voltmeter.TerryComment
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