does anyone on here have a complete diagram of the vacuum routing on a 1979 corvette

 

For the headlights?

 

You're in Louisville, Drop by our store and sales should give you either one. I'll see if I can post one to our site tomorrow, this may save you the trip if your in the outer edges of town.

Willcox

 

where at in jeff are you located and whats your hours??? i live out in prp so its not a far trip for me to go anywhere in town and i need this routing to get my car back on the road... bubba really fixed me up on this one

 

Exit 0 off the Kennedy, go to to the bottom of the ramp and turn right on Court Ave., three blocks turn right on Wall, one block turn right Maple. The parts store is the second building on the right. You never said if it was the headlamp system.


Local call for you, 288-7103.
Willcox Inc.
123 E. Maple Street.

Hours 9 - 5 M - F.

Willcox Inc.

 

yes for the headlights.. they go down if i stick a vacuum pump on them but i cant get them to raise so i need to figure out whats wrong with them.

 

 

When I’m done writing these vacuum diagnostics I’m going to post them. Someone should make a sticky out of them.

First, where are you sticking the vacuum pump to power up the headlamps?

First let’s get some testing done. Copy and print Rogers vacuum schematic, it’s correct! Next I want you to go to this link and print out this page on the operations of the parts in the system. It will help you understand what is going on where in the system. http://willcoxcorvette.com/repairand...lp.php?hID=218

Ok, now let’s move forward!

Start the car and let it come to operating temperature.

Pull the hose off the intake fitting and take a vacuum reading at the manifold.

Let’s say the reading is 17 hg. at the manifold. At any point in the system you should not have a leak more than 1 hg. of vacuum.

The front bumper of the car has a vacuum reserve tank built in to it. Block off the smaller hose running in the car to the headlamp switch. (This will take all the inside parts out of the system for now). Pull the hose off the brass fitting on the drive side of the vacuum tank. Take a vacuum reading at this hose and see if it is the same as the intake. Any drop here means you have a leak between the intake and the reserve tank.

If the car pass’s pull the vacuum hose off the passenger side of the tank and take a reading. This will tell you if your tank is leaking. If the car pass’s this test then I want you to reverse the top and bottom hoses on the vacuum actuator relay at the header bar. (Switch the green and red hoses). Attach the small vacuum hose back to the check valve and turn on the headlamps. Do they come up now? If they do, you have eliminated the actuators as being the problem. If they don’t come up, you have an actuator problem. (Switch the hoses back now).

This same system of checks can also be done on the vacuum control hose (small hose’s).

What controls the headlamps up and down is the headlamp vacuum actuator relay combined with the headlamp switch operation.

http://willcoxcorvette.com/product_i...oducts_id=4815

To see how this operates go to this link. (scroll down, it’s on page two. http://willcoxcorvette.com/repairand...lp.php?hID=218

The large nipple on the top is the pull down side which in normal operation is pulling the lid down. When you turn on your headlamps this cuts the vacuum to the small hose and the relay switches vacuum to the lower large nipple which will raises the headlamps. (Just as if you pulled the over-ride valve under the steering column).

So now you know how it operates, let’s check the vacuum on the hose with the car running headlamp switch off. Pull the nipple off the small tit on the relay. If you have good vacuum at the small nipple on the relay, pull off the top hose and see if you have vacuum on this nipple. If you do, go to the car and pull the over-ride switch. Did the headlamps raise? If not, go the lower hose and see if you have vacuum.

If you do not have vacuum, then you should consider replacing the relays.

Now. . . The dreaded headlamp switch and over-ride.

We’ve covered most everything and how to test so lets hit these two and be done.

The headlamp switch and the over-ride switch should both be passing vacuum with the switch turned off and the over-ride in the off position. So to the vacuum T at the headlamp relays and pull off the feed hose running from the over-ride switch. Do you have vacuum and is it within range? If the car pass’s this test, go inside and pull the over-ride switch. You should loose vacuum on the small hose. (you really don’t need to do this but it’s just checking the over-ride). If you don’t you have a bad over-ride switch.

Now go inside the car and pull (And yes Rogers diagram is correct to a T) the bottom hose off the over-ride. Start the car and see if you have vacuum, if you do take a reading.
With your vacuum gauge hooked to this hose, now pull the headlamps on. Did you loose vacuum? If not, you have a headlamp switch problem.

Ok. . . Now go test it. Please remember it’s late, I’m tired and if I’ve made any mistakes it’s about 2 hours past medicine time.

Regards,

Willcox Inc.