InTheSkin

I have been troubleshooting this on and off for a few weeks now. I am about at my wits end. I realize I am asking questions that have been covered on here before, because I have searched. A lot. I need to get this discussion started because I must be missing something.

The car is a 71 factory BB/auto car, now sporting a ZZ502 and 700R4. Factory AC car, this system not complete right now. The car was my dads, he left it to me when he passed. He had installed Holley Projection/Commander 950 EFI in the 90s, but it never ran right. After I got it, I opted to swap back to carburetion. Dad kept all the old parts. That job is done, and everything starts and runs fine. While it was in the shop, I did a Borgeson swap and generally cleaned up the engine bay of old wires. The car drove into the shop, with the wiper door and headlights closed.

I don't know if the wipers worked before because the car never saw rain. I suspect they did work. But now, the wipers are non responsive. The fuse is good. The dash switch does nothing. I did figure out the vacuum switch under cowl on the passenger side is bad, so I have one of those on order. In the mean time, I capped the lines going to it and tried again to lower the door and lights. no good. Attached is a pic of the wiper motor with a spade terminal that looks like it used to have something connected to it. From the looks of things, it is just a ground. What should be on this?

I didn't knowingly do anything to any vacuum lines other than to inspect and verify everything was in good serviceable condition. The vacuum tank inside the left fender appears to be in good shape.

I have wiring diagrams and vacuum diagrams. I understand that these systems fail open on loss of vacuum. I have had the vacuum source hooked to both the base of the carb, as well as the boss on the manifold. It makes no difference. The push/pull pots under the steering column do nothing. I don't have a filter in line from the vacuum source. I have a new check valve.

At this point, I am not overly concerned about the wipers working, as I have no intention of driving in the rain. I will get them working in due course, but for now, I'd like to have the headlights down and the wiper door closed.

I think those are the high points. Any feedback is greatly appreciated.

--Mike

0Willcox Corvette

Is the wiper door open? Are the headlamps up?

I can get your wipers and headlamps working but we'll need more info. By default both are designed to open when there is a failure on the small hose side (black/white stripe).

The system should use vacuum off the manifold... For the headlamps to close you must have vacuum on the hose marked 2 below. So start there and pull the hose off the relay and see if there is vacuum. If there isn't any, then work backwards by going inside the car and pulling the hose off the headlamp over-ride and see if you have vacuum there. If you don't then go to the solenoid and so on...

For the wipers it's pretty much the same... but for the wiper system to work, the door must be all they open and the limit switch plunger must be depressed inward. (the limit switch is to the left of your red circle). You can test the switch by pressing the plunger inward and seeing if you pass continuity from one side to the other. Are you hearing any noise when you turn on the wipers?

You'll need to get the vacuum system working on the wiper door or pull it open and disconnect the actuator for testing the wiper system.

InTheSkin

Hi Willcox;

Yes, lights and wiper door are both open.

Right now, i don't hear any noise when I try to turn on the wipers.

No discernible vacuum at 2, or at the over rides. Good vacuum going to the tank in the fender, and good vacuum in the yellow hoses at the headlights and solenoid F

InTheSkin

Where does the brake booster fit in to the system? Neither your diagram nor others I have looked at show the brake booster as part of the system. When I got it, the large port off the check valve went to the booster, and the small port went to the vacuum tank. I have isolated the booster until I get the rest of the system figured out, so right now, all I have is one port off the check valve going to the vacuum tank.

Alan 71

Hi INS,
The brake booster vacuum supply is completely separate from the wiper door and headlight doors systems.
The typical line for the wiper/light systems starts with a short rubber hose to a filter, a sort hose to a check valve which also splits into 2 lines… a small hose for the 'control' part of the system which heads to the dash through a grommet in the firewall, and a large hose for the 'servo' part of the system which heads to the vacuum reserve tank.
This is a typical appearance.
Regards,
Alan

InTheSkin

OK, that helps a lot. I'm going to pull vacuum for the brakes off the base of the carb, and another line per your picture off the manifold fitting.

0Willcox Corvette

I forgot too, that terminal you have the circle around is a ground terminal.

Okay.. dig deeper, no vacuum at 2 will keep the relay's in the up position so you need to get vacuum from the headlamp switch to there.

You said you had vacuum on the yellow hose at the relay F.... do you have it on the black/white stripped small hose?

Willcox