Redvette_22

Today I replaced the broken vacuum hose on the headlamp switch in my 72 Vette, and although I've only had the car a short time, and the headlamps did not go down since I bought it, I figured replacing the broken hose would take care of it. When I was buying the car the owner told me the headlamps would not cycle, and there was a major vacuum leak from behind the dash, which was the broken hose, but the windshield wiper door and wipers worked. With replacing the hose, and confirming the routing with the diagram from both Wilcox and Zip, this now happens. The vacuum leak is gone, as expected, but when you pull the headlamp switch rod, the wiper door opens but the wipers don't cycle. If you move the wiper switch, the headlamps come up but don't turn on. The headlamps will turn on, if you pull the headlamp ****, but then the wiper door opens again...... Has anybody seen this happen, nothing I tried, including swapping hoses let the wipers turn on, and the doors opened just like before, wiper switch opens headlamps and headlamp switch opens wiper door only?

Easy Mike

You have crossed up headlight vacuum and wiper door vacuum. My hunch would be the vacuum lines on wiper door solenoid on the back of the tack.

Alan 71

Hi LB,
What is the result when you pull the vacuum override switches below the steering column… the left side is for the headlight doors and the right side for the wiper door.
These switches by-pass the headlight and wiper switches on the dash.
This will begin to tell you where the hoses are crossed.
Do you have the AIM sheet that shows the hose routing behind the left side dash pad?
Do you have access to those hoses now?
Regards,
Alan

You need to have UPC 12, Sheet B9 in front of you to trace the vacuum hose routing and connections. One sheet shows both the wiper and headlight hose routing.

The wiper door safety switch, which is mounted on the firewall, must be be triggered by the wiper door linkage in order for the wiper motor to run. Have you checked to see if the 'button' is being pushed when the door opens?
Here's the 'plunger' that pushes the button on the switch. It completes the circuit to the wiper motor.
Have you checked it?

Rescue Rogers

On a 68, the vacuum tees then goes to the headlight switch and tach sloenoid from there. yours should be the same. the only place they can be crossed and function are at the maintenance/ over ride switches. The wipers should function when the door is open, you mat have 2 problems. Fix the the doors first, then figure out the wipers. You may just have the wiper over ride switch turned on.

Redvette_22

I am waiting for the assembly manual to come in, but as I mentioned, I have the ZIP and Wilcox hose routing diagrams, do they have the same information you refer to UPC 12, Sheet B9..?

As far as the "override" switches go, when I pull the LH one, the headlamps do go up, and when I pull the RH side the wiper door opens. The complete dash is out so I have decent access to all the "underdash" parts and when I removed the LH side, I found the hose cut from the headlamp switch to the tach solenoid, which I replaced (working on one hose at a time). When I bought the car, the headlamps were in the "up" position, and there was a massive vacuum leak behind the dash (broken hose to HL switch), but the wiper door worked fine...if not just a little slow.

I did find this afternoon that the "wiper vacuum switch on the firewall" is broken and the spring under the plunger is hanging out.

Alan, your car looks fantastic..!!

Redvette_22

When I took the dash out (cleaning, checking wiring, etc.) there was only one hose that was broken, and it went to the HL switch, so I replaced it, and that is when this all happened. As a precaution, I did try to switch the solenoid vacuum hoses, but it did not correct anything.

Rescue Rogers

Rescue Rogers

I think you may have #8 hose and letter H hose switched or #1 and letter G, YOu may want to trace all your hoses and get close to this diagram, Your year may vary but should be similar

CanadaGrant

The only way it can work like that and it will, is if you have the vacuum lines reversed on the solenoid on the back of the tach. The diagram is correct but the solenoid is reversed orientation (facing the wrong way) in the Wilcox pic compared to the car. The vacuum hose off the T-fitting goes in the end without the sponge filter vent. The hose from the filter vent end goes to the wiper override pull down switch. Just reverse the hoses end for end on the wiper solenoid and you should be good to go. If these two hoses are mistakenly reversed on the wiper solenoid the override switches will work properly but the headlight switch and wiper switch vacuum functions are crossed.

Redvette_22

It looks like the #8 hose & H hose may have been the culprit. The wipers still don't work but that I believe is due to the wiper vacuum switch on firewall, being broken, as I mentioned yesterday. Once I get a new one of them from Corvette America, all should be good. Thanks for the help...

Rescue Rogers

anytime