71' Headlight Vacuum Problem
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Joined: Feb 2002
Posts: 93
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From: Gulph MIlls PA
71' Headlight Vacuum Problem
Yes, another VACUUM problem on a 71’ 350 Roadster. I replaced:
1. All vacuum lines.
2. Wiper Door Actuator
3. Wiper Door Relay
4. Solenoid/Vacuum Switch in back of the tachometer.
Symptom: The wiper door and headlights open and close immediately, using the override switches under the steering column. The problem is that it takes the headlights up to 1 minute to open, after turning on the headlight switch. For what it is worth, headlights close immediately when the headlight switch is turned off.
We’ve been using the Doc Rebuild troubleshooting guide. My understanding is that the vacuum must be “released” for the headlight buckets to open. We tried replacing 1 of the 2 headlight vacuum relays, but it had no effect.
I’ve read many other vacuum problem posts, but I’m having trouble identifying the problem.
Any help would be much appreciated!
Thanks!
:confused:
Racer
Joined: Dec 1999
Posts: 485
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From: MESA, AZ, USA
Re: 71' Headlight Vacuum Problem (TQ67)
I'd have to say the headlight vacuum valve is not opening the control line going to the vacuum relay. When you turn the lights on the valve ties the vacuum directly to the top of the relay. This applies vacuum to both main canisters for the headlights and opens the headlights. When you turn the lights off the valve is suppose to seal the vacuum source going to the headlight sw. and open the control line going to the control valve. If the "vacuum" in the control line isn't released the relay will continue to "tell" the headlights to stay open. Once the vacuum leaks off the doors close.
Put a vacuum gauge on the vacuum control hose going to the top of the relay valve and watch the vacuum as you active the headlights. A vacuum will build quickly when you turn the lights on, but drop slowly when you turn the lights off. Using the over-ride the vacuum will build quickly and drop quickly. So the problem is the vacuum valve at the headlight switch.
Give it a try.
Andy
Put a vacuum gauge on the vacuum control hose going to the top of the relay valve and watch the vacuum as you active the headlights. A vacuum will build quickly when you turn the lights on, but drop slowly when you turn the lights off. Using the over-ride the vacuum will build quickly and drop quickly. So the problem is the vacuum valve at the headlight switch.
Give it a try.
Andy
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Joined: Apr 2001
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From: Was New Orleans but swam to Baton Rouge LA
Cruise-In IX Veteran
Re: 71' Headlight Vacuum Problem (TQ67)
My headlights were doing a similiar thing when I first got my car. I did not think it was a problem until they stopped working. The vacuum relay valve to the wiper door was the culprit. I replaced it with a new one and now everything operates quickly. You might want to also check that relay with the headlight relays.
Mark B.
Mark B.
