Blinking Headlights & Wiper Door

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Sep 28, 2010 | 12:26 AM

brockbenson

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Blinking Headlights & Wiper Door

Hi Everyone,

I'm sure someone out there has seen this problem before.

I have recently rebuilt and/or replaced all my vacuum operated equipment on my 1970 vette.

It's all back together now and working, except for the following oddity.

When I start the motor, the headlights and wiper door pop-up for a second or two then close again.

When I operate the light switch or wiper switch (with motor running), they open and close as they should.

It seems to be something with the amount of vacuum reaching the relay valves maybe or how quickly it is building vacuum? I have had no luck troubleshooting it though.

Any thoughts or experiences would be welcome.

Cheers,

BB

Sep 28, 2010 | 01:59 AM

Solid LT1

Le Mans Master

Joined: Dec 2003

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From: Fremont CA

Bad check valve from intake manifold to vacuum tank is where I would start looking to solve your problems.

Sep 28, 2010 | 04:47 AM

brockbenson

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Solid LT1,

That was the first thing i checked too. The valve is new. But I tested it anyway, to verify vacuum flow only travelled in one direction (into the intake).

Cheers,

BB

Sep 28, 2010 | 10:25 AM

7T1vette

Team Owner

Joined: Jan 2006

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From: Crossville TN

The check valve is installed backwards. The engine 'sucks'...not the headlight/wiper system.

Sep 28, 2010 | 06:18 PM

brockbenson

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Hi 7T1vette,

It can't be the check valve fitted backwards, for two reasons:

1. The valve can really only fit one way. It has one port on the manifold side, and two ports on the opposite side (one to the vacuum tank other to headlight switch / wiper solonoid).

2. If fitted backwards, nothing would work because there would be no vacuum to any components. As I mentioned above, both systems work fine, but blink when the car is first started.

Thanks anyway, but does anyone else have any ideas

Sep 28, 2010 | 08:08 PM

wombvette

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Joined: Jan 2000

Posts: 8,918

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From: New Hill NC

Quote:

Originally Posted by brockbenson

Understanding how the system works will help. The signal line (small one) tells the relay valve which way to direct the vacuum to the actuator. The headlights default to the up position, which means they come up if anything in the signal circuit quits working. When you start the car and the vacuum is already low and there is a leak in the signal line, the headlights will pop up by default. So whats happening is the vacuum in the large line comes up before the signal line. There is either a restriction or a leak of some kind in that circuit causing slow behavior.

Sep 29, 2010 | 02:03 AM

brockbenson

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Thanks Wombvette,

I think we are both on the same track here. It seems to be a timming issue. How fast vacuum is building up on the signals side versus the control side of the vacuum system.

I have checked and double checked everything. My dash is out, so I know there are no pinch hoses, or leaking hoses there. Besides the headlight actuators and wipe door actuator, eveything else is new. Including the hoses, headlight switch, over-ride switches, wiper solonoid, and relays.

None of the vacuum hoses have clamps on them, and they don't from the factory, so i can't imagine a vacuum leak there.

Logic dictates that vacuum should build up much faster on the signal side due to the smaller diameter hoses and smaller components vs the control side which has to evacuate the larger diameter hoses and all of the vacuum tank!!!!

So there must be a leak somewhere ???? But where, and how do I find it.

Can anyone else suggest anything.

Cheers

BB

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