71 Head light doors stuck open

[Robert P.]

The only way I can close them is by hand. When I start the car they open. pulled off the vacuum line and it has vacuum. I closed the head light door and plugged in line and it opened. Aren't they suppose to close under vacuum? Thanks for any help Bob

[Patrick H.]

Re: 71 Head light doors stuck open

Aren't they suppose to close under vacuum?

Yes... and no.
Note that there is a red line and a green line going to the canister, one in front and one in back. The red closes the can, the green line opens it.

You may have a hose that fell off, a vacuum relay that went bad, or a leak in a canister. Other issues can also cause this problem.

Consider visiting Doc Rebuild's site and buying the vacuum system troubleshooting guide. For $3.95 it's a heck of a deal.

Sample hose schematic:

http://www.docrebuild.com/dr-r-web/DROOPY2.HTML

Vacuum troubleshooting guide:

http://www.docrebuild.com/dr-r-web/A-TROUBLE.HTML

Patrick

[Jack H.]

Re: 71 Head light doors stuck open

Adding on to what Pat had to say, having a copy of one of the different vacuum system troubleshooting guides and reading it will help you understand the system a LOT better!

The system is actually TWO systems that work in parallel. One side is called the 'servo' system. That's where vac is used to do actual work (open this, close that)...

The other side is called the 'control' system. That's where vac is routed to various switching components to tell the servo side WHEN to open/close this/that item.

The control side of the system is intended to come up first when the engine starts running and 'fall down' last when the engine has stopped running and stored vac bleeds off. That's intentional... It keeps the actuating parts from 'twitching' during startup and shut down.

The control side of the headlight door runs from the check valve on the smaller of the two vac tubes. It routes through the firewall and into the cockpit. From there it runs to the headlight over ride switch (under the steering column) on to the vac side of the headlight switch and back out through the firewall to the headlight vac relay(s).

The truth table for actuation is venting vac at either/both of the cockpit switches = the instruction to open the headlight bucket(s). So, that's where you start to find out where your problem(s) are!

Any time someone's been 'playing' with the instrument cluster, you've got the making for a problem. Forgetting to connect one of the vac system's headlight control lines renders the system opening the headlight doors permanently because control vac is being vented...

[Robert P.]

Re: 71 Head light doors stuck open

Thanks for the replys, I checked the connections ,they are okay. the only one I can't get to is the headlight switch. I just installed the steering column, all the hoses are connected. the wiper door works okay. I checked the red hose on the head light actuator and there is no vacuum. Thanks again Bob

[Don L.]

Re: 71 Head light doors stuck open

Hi Bob. Since you've recently been under the dash, R & R'ing the column, I suspect/hope a line just got pulled off inside the car. Check your overide switches and the lines going over to the light switch. I've had luck with mine before by removing the left dash panel screws (3 along top and 2 @ door jamb) and gently pulling the dash back a little bit to give you access from the jamb end. You'll likely cut your hands a little, but vs pulling the whole left dash out just to see if it's there or not is well worth a few scabs for a week.

[Robert P.]

Re: 71 Head light doors stuck open

Don, Dave did a nice job on the column, everything works. I had the car out today. June 5 is coming fast, still have a few things to do. Now with the vacuum problem it is going to be tight. Bob

[Don L.]

Re: 71 Head light doors stuck open

Great to hear that Dave hooked you up with the column repair. He rebuilt mine as well. I took it in to have the correct ign key installed and the T/T mechanism was a broken bunch of junk inside. It's now like brand new! The guy is a genius. I'll share more when we see each other at the upcoming meet.

Good luck with the vac issue. You've gotten some good advice and tips here today. If all else fails, you might just have to take it to Dave for that too.

[Gerard Q.]

Re: 71 Head light doors stuck open

Have you checked that the over ride switch is not pulled down and that it is plumbed correctly?