Vacuum Leak in headlights

[Kim B.]

I need some help in regard to my '70 LT1. When I start the car and pull the light switch the car looses RPM and will die if I don't give it throttle. I don't have this problem when I use the manual override switch. No problems with the wiper door at all. I have tried to run down every hose, switch, relay and actuator. All hold vacuum or were replaced. The whole system is new. I know I have a vac leak somewhere, car has a very erratic idle. I have gone through all the help manuals, but have ran out of ideas. Have any of you had this problem??

[Patrick H.]

Re: Vacuum Leak in headlights

I would highly recommend getting the vacuum system troubleshooting guide from Doc Rebuild. It will tell you more about each component than we can online here.

Having said that, if you get zero issues when you use the override switch but problems with the actual headlight switch then I would suspect a leak in the hoses going to the switch or in the headlight switch itself. It sounds like it is allowing significant amounts of air to enter the system. And, don't assume that just because the switch is new that 1) it's not defective and 2) it's the problem.

Good luck!

[Alan S.]

Re: Vacuum Leak in headlights

Hi Kim,
Following along with Patrick's suggestion about the headlight switch.... SOME of the literature, (including some years of the AIM), show the 2 small vacuum hoses leading to and from the switch, backwards. The blue striped hose should connect at the forward nipple, while the plain black hose connects to the rear nipple.
Have you checked yours?
Maybe an easy fix?
Regards,
Alan

[Bill L.]

Re: Vacuum Leak in headlights

I concur with Alan. I bought the guide from Doc Rebuild and traced everything out. Found three marginal components. Kinda neat to watch headlights work when they are right



Bill