Input needed on headlight issue
Thread Starter
Racer
Joined: Mar 2008
Posts: 434
Likes: 0
From: Triangle Area NC
Input needed on headlight issue
I've rebuilt my never-functioning (at least as long as I owned the car) headlight assys. When I manually operate a vacuum pump on the 2 ports of the actuator I can make the lights go up and down. Even my dim brain tells me those are working right .
I get vacuum from the engine and it holds it in the front crossmember "tank" (this is on a 74 car). That sounds good.
Moving to the relays , I have the following situation. When I plug the vacuum gauge to the small diameter hose that comes to the vacuum relays, there is plenty of vacuum when the engine is running and the lights are OFF, and there's no vacuum when the engine is running and the lights are on.
Does that latter situation sound back assward to you, or is it the correct logic. Again, I'm measuring this last step at the control line (small diameter) to the two vacuum operated actuator relays.
Needless to say, the lights dont raise when the hoses are all connected. Since I can operate them with a China Freight vacuum pump, I'm pretty sure that with full engine vacuum applied in the right state, they should work fine.
Thanks for the input
John
PS: Actuators have been rebuilt.
I get vacuum from the engine and it holds it in the front crossmember "tank" (this is on a 74 car). That sounds good.
Moving to the relays , I have the following situation. When I plug the vacuum gauge to the small diameter hose that comes to the vacuum relays, there is plenty of vacuum when the engine is running and the lights are OFF, and there's no vacuum when the engine is running and the lights are on.
Does that latter situation sound back assward to you, or is it the correct logic. Again, I'm measuring this last step at the control line (small diameter) to the two vacuum operated actuator relays.
Needless to say, the lights dont raise when the hoses are all connected. Since I can operate them with a China Freight vacuum pump, I'm pretty sure that with full engine vacuum applied in the right state, they should work fine.
Thanks for the input
John
PS: Actuators have been rebuilt.
Burning Brakes
Joined: May 2005
Posts: 1,145
Likes: 5
From: South of London, Engerland
I believe that the headlights will default to the up (safety) position if the control vacuum in the small pipe is removed. So it sounds to me like the control circuit is working. So, if you disconnect the thin pipe with the engine running, do the lights pop up?
Thread Starter
Racer
Joined: Mar 2008
Posts: 434
Likes: 0
From: Triangle Area NC
No they don't.
I can't remember which is which, but I can pump UP the lights by attaching the vacuum pump to one side of the diaphragm and lower them by applying vacuum to the other side.
I can't remember which is which, but I can pump UP the lights by attaching the vacuum pump to one side of the diaphragm and lower them by applying vacuum to the other side.
Burning Brakes
Joined: May 2005
Posts: 1,145
Likes: 5
From: South of London, Engerland
So far you've established that the actuator seals are good, because you can raise and lower the lights by applying vacuum to the pipes leading to each actuator.
You've established that there is good vacuum in the thin diameter control pipe.
Next you could try checking that you have good vacuum in the pipes that feed the relay valves from the accumulator tank. Disconnect one pipe at a time from a relay and check vacuum there. If you have vacuum in each of those two pipes then you have a relay problem. If you discover no vacuum in either of those pipes then you have a vacuum leak between the engine and the relays in the non-control side.
You've established that there is good vacuum in the thin diameter control pipe.
Next you could try checking that you have good vacuum in the pipes that feed the relay valves from the accumulator tank. Disconnect one pipe at a time from a relay and check vacuum there. If you have vacuum in each of those two pipes then you have a relay problem. If you discover no vacuum in either of those pipes then you have a vacuum leak between the engine and the relays in the non-control side.
Thread Starter
Racer
Joined: Mar 2008
Posts: 434
Likes: 0
From: Triangle Area NC
Will do that as soon as I get home tomorrow, and will post the results here. Thanks very much , I REALLY want to see those things go up someday soon!
Thanks for your help.
John
PS: By the way, all hoses to and from the relays to the actuators and the accumulator are new.
Thanks for your help.
John
PS: By the way, all hoses to and from the relays to the actuators and the accumulator are new.
Burning Brakes
Joined: May 2005
Posts: 1,145
Likes: 5
From: South of London, Engerland
A friend of mine with a '79 has a leaking accumulator tank, so the tank has been bypassed in his headlight system. Clearly leaks are possible (but I don't know how!).
I hope someone else will confirm that I'm right with my diagnosis so far. I think I know how the system works but it's 1:43am here in England and my brain's getting a little slooooooow.
The crucial thing is that you must have strong vacuum both in the control pipe and in the pipes leading from the tank to each relay.
If you connect a headlight actuator front pipe directly to the tank, does that light pop up?
Good luck with it
I hope someone else will confirm that I'm right with my diagnosis so far. I think I know how the system works but it's 1:43am here in England and my brain's getting a little slooooooow.
The crucial thing is that you must have strong vacuum both in the control pipe and in the pipes leading from the tank to each relay.
If you connect a headlight actuator front pipe directly to the tank, does that light pop up?
Good luck with it
Melting Slicks
Joined: Jul 2004
Posts: 2,577
Likes: 2
From: Long Island New York
Are your relays original? If so I am going to bet on them being the problem. I had the same situation as you, I replaced everything in the system and still no dice. I tested the relays with a hand pump and they tested fine. I finally gave up and replaced them, they were the only thing in the system that wasn't replaced and now my headlights work fine.
Thread Starter
Racer
Joined: Mar 2008
Posts: 434
Likes: 0
From: Triangle Area NC
two steps forward
Are your relays original? If so I am going to bet on them being the problem. I had the same situation as you, I replaced everything in the system and still no dice. I tested the relays with a hand pump and they tested fine. I finally gave up and replaced them, they were the only thing in the system that wasn't replaced and now my headlights work fine.
I pulled the line that goes to the accumulator and hooked it to the front and back of both actuators. Happily, both raise and lower quite smoothly and quickly. YAY!
Now it's looking like the relays. How weird that they both fail. I'll make sure that the lines are not leaking,etc , but its sure looking like they may be bad.
Nice to see the restored actuators working so well anyway!
John
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Burning Brakes
Joined: May 2005
Posts: 1,145
Likes: 5
From: South of London, Engerland
It may not be both relays- if one of them has a serious leak then it'll affect both sides of the system. Again, disconnect one side at a time (control side then power side) and plug the open pipe and operate the lights. You might find that this narrows down the problem to one side only. 
Thread Starter
Racer
Joined: Mar 2008
Posts: 434
Likes: 0
From: Triangle Area NC
Yep! It was the relay. I rebuilt one with the o-ring fix that's been referred to, and it now works like a champ. I'll hit the other one tomorrow.
Thanks for the help. One fix at a time!
John
Thanks for the help. One fix at a time!
John