Hello Everyone,
I'm working on my '68 Corvette.
I've got a strange one I just can't trouble shoot.
When I start my car the wiper door and both headlights rise.
When I pull on the head light switch, the wiper door closes.
After vac builds up I can shut off the headlights with the switch
and both headlamps close in near unison smartly.
They will stay down as long as I'm running.
I can open and close the headlights 2x then the vac has to build up
again before it will work while running.

Here's what I did.
A new and tested filer and check valve.
Both replacement headlight actuators tested and both relays rebuilt.
Actuators GM take offs, relays after market but rebuilt anyway.
All tested and hold vac.
All new lines.
New OEM headlamp switch just installed today.
I tested it first.
2 new over ride pull downs. Again tested.
Tach solenoid tested and working while I had dash out.
Wiper Actuator a new replacement.
Wiper side seems good. It works off the switch, and pull down,
and over ride. All good.
When I put the wipers on the headlights do not come up.
I have a problem somewhere on the control side involving the head light circuit.
It was doing this so I replaced the headlamp switch and still same.
The control line is hooked up to the port closest to the head lamp ****. Blue line to the back.
I am truly stumped and mentally exhausted trying to figure this one out. I'm getting closer as everything works now except I have this issue.
Thanks to a Great Forum for your responses.
Marshal

 

The "HOT" vacuum hose to the headlight switch is supposed to go in the front (opposite the pull ****) and that's where your problem probably lies. By dropping the steering column down about 3" and taking out the dashboard screws you can pry the dash apart enough to gain access to those two hoses OR you can switch their places down below.

 

Hi Marshal,
I believe tb is right.
There are drawings around that have the 2 hoses on the wiper switch reversed…. (the 71 AIM for example)….so the one you're referring to MAY be misguiding you.
The 'control side' vacuum supply hose (white stripe) comes through the firewall and leads to the upper nipple on the headlight override switch.
A blue striped hose leads from the lower nipple on the override switch to the front nipple on the headlight switch.
A plain black hose then runs from the rear nipple on the head light switch to a 'T' near the valve on the back of the tach.
One hose from the 'T' attaches to a nipple on the valve, while the other hose from the 'T' goes back out through the firewall and forward to the headlight relay.
In working on the the vacuum systems I always try to separate the parts into to 2 'sides'… the 'Control Side'…. small diameter hoses, switches, and relays, and the…. 'Servo Side'…. large diameter hoses and actuators.
Good Luck!
Regards,
Alan

 

I actually painted my hoses and their nipples: red for the HOT and blue for the NOT HOT (a little joke) so I could never mix them up.

 

Good idea. When I had the hoses switched I heard a vacuum leak on my '77.

 

Could you please explain exactly which vacuum hose goes to your Blue port, and which hose goes to your Red port?

Is your definition of a "HOT" hose one with vacuum always present?

Is your definition of a "NOT HOT" hose one without?

Thanks

 

Still waiting for your answer to my question kind sir

 

 

Hi K,
You know, you're right, I should have been silent!
I was trying to be humorous.
Regards,
Alan

 

 

Alan,
You are so right, I looked at two different schematics for hose routing and they both differ as to which port the control side connects.
Right now, I have the control side off the check valve, tee'd into the
tach solenoid and on the port closest to the pull **** of the head lamp switch.
The blue line is on the rear port, closest to firewall when installed,
then connected to the HL pull down. The white striped line from the pull down to the top of the single HL relay (68)

I thought I understood this system well enough to give others advise,
that is until this started. I have no clue what I'm doing wrong.
I know I'm real close to having this system working again.
Thanks,
Marshal

 

I appreciate Alan's humor without that this forum would just be an info blog. Im the original Joker at work HA HA.
Marshal

 

Jim,
when you had the hoses switched did your head lamp switch close the wiper circuit as well?
My HL switch is acting in reverse.
Marshal

 

According to your color coding, if the vac line from the check valve belongs on the red port, I do have them switched.
Marshal

 

Alan,
If you recall, in your above pic does the line attached to the port closest to the HL switch pull out **** come from the check valve (teed line to tach solenoid) or the blue striped line leading to the pull down?
I'm getting warmer.
Thank you for the pic.
Marshal

 

That is correct! The vacuum source hose ALWAYS goes to the port closest to the pull ****, whether it is the headlight switch or the override. The reason is that port is BLOCKED when the pull **** is pulled out. The port farthest from the pull **** is the VENT. It's function is to vent the vacuum (or allow atmosphere) into the circuit thus moving the internal piston inside the relay(s). If the hoses were reversed, there would be a massive vacuum leak in the control system.

The override switch operates in the same way. The hose from the vacuum source, whether that is the h/l switch or the wiper door solenoid goes to the port closest to the pull **** for the exact same reasons as above.

Do you still have my number?

 

Here's the AIM with colors:

 

And here is Willcox's 100% CORRECT vacuum hose route diagram

 

Dave,
I have it plumbed exactly as the Wilcox diagram.
I thought you taught me right
When I start the car the wiper door and both head light doors open.
After vac builds I can pull out the head light switch to head lights
on position and the wiper door will close.
Given a short drive period, I can push in the head light switch to off
and both HL doors snap shut smartly. They will repeat this after I shut the car off for like a 1/2 hour or more. If I run in for an errand everything will remain shut.
The old switch was doing the same and the rheostat was burned out.
I thought the switch was bad x2. A leaker and shot rheostat.
Now rheostat works great but vac issue still exists. I tested new HL switch prior to installation as you instructed me in an earlier PM.
I do still have your number.
I'm working night work tonight, I will call you daytime Thursday if that is ok.
Thank you,
Marshal

 

the humor is always welcomed and encouraged, hell with out it I would probably be banned from here.