1969 1970 Headlight Door Vacuum Troubleshooting

Hello everybody. I have searched this site, YouTube, and the Internet in general, for a “one stop shop” guide to troubleshoot the vacuum system for the headlight doors, in my case a 1969 Eliminator. I had a minor leak in my headlight door actuator, so I replaced it with a rebuilt one from Critter Creek Cougar (through National Parts Depot). Two days later, my headlight doors were open again. I know I need to start looking at the check valve, vacuum storage tank, and rubber lines, but I’m wondering is there a sequence that makes sense- for example start here and work your way there. I did read on here about how to test the storage tank by presurizing and submerging in a tank of water, but what about the check valve, rubber lines, and even the headlight switch? Is there a process to test them? Thanks in advance. Oh, before anybody recommends going electric, my car is all stock so I would prefer to keep it all original.

Don Rush, if you’re reading this, I think this would be great for your next “how-to” video!

New to the group, but this was actually my first project task as I tackled my first 1970 cougar, now have a 1969. Both had the same issue. Both equally frustrating to nail down, hence why I went the electric direction, but after getting everything out, i realized time spent on cracked hoses and that tank in the inner fender could have gone a long way to keeping that vacuum system working perfectly. Just my 2 cents, so I hope someone here has some good thoughts to help you along.

Thanks for the insight!

I used a Mighty Vac vacuum tester. Checked the actuator. The tank, took off the hoses and tested rach pipe one at a time, which found my problem. It was the supply line to the tank. The switch was changed out already because of a short for the dash lights caused by having the aftermarket radio grounded thru them. Off topic. But the 2 position plug for the stock radio is radio power and backlight power. Not ground.

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You said doors were open after two days. FWIW, the original warranty spec was 18 hours closed. I know because my 70 actuator was replaced under warranty the first year - it’s a one owner and I keep records.

Since then I’ve tracked down small leaks multiple times. It’s most often the hose ends (last 3/8 inch) that lose grip. Mine are original hoses, some cut down a bit to get better grip.

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