Early C3 vacuum experts?
Thread Starter
Drifting
Joined: Aug 1999
Posts: 1,451
Likes: 84
From: Round Rock TX
Early C3 vacuum experts?
My wiper door opens when I turn the switch on, and closes when it’s off. So it operates as it should. My headlights open as they should when turned on, however the wiper door opens as well.
Any experts with a suggestion on where to look? Everything seems to be connected properly. The headlights open with authority (quickly).
Any experts with a suggestion on where to look? Everything seems to be connected properly. The headlights open with authority (quickly).
Team Owner
Joined: Sep 2006
Posts: 31,198
Likes: 4,287
From: Westminster Maryland
Hi D,
What year of 68-72 car matters because of where the wiper door vacuum relay is located.
When the wiper door opens because you've pulled the headlight switch... does it close when you shut the lights off?
Regards,
Alan
What year of 68-72 car matters because of where the wiper door vacuum relay is located.
When the wiper door opens because you've pulled the headlight switch... does it close when you shut the lights off?
Regards,
Alan
Le Mans Master
Joined: Apr 2001
Posts: 5,941
Likes: 281
From: Was New Orleans but swam to Baton Rouge LA
Cruise-In IX Veteran
I would look at the override switches and the wiper door solenoid as the possible issues. These should be the only two vacuum controls that share lines with the headlight switch. First though you need to make sure someone did not route the hoses incorrectly or splice into something headlight related.
Team Owner
Joined: Sep 2006
Posts: 31,198
Likes: 4,287
From: Westminster Maryland
Hi D,
You didn't answer my second question, does the door close when you push in the light switch?
As Sig suggested look at the routing of the hose from the headlight switch to the solenoid on the rear of the tachometer and from the solenoid to the wiper door override switch.
Regards,
Alan
You didn't answer my second question, does the door close when you push in the light switch?
As Sig suggested look at the routing of the hose from the headlight switch to the solenoid on the rear of the tachometer and from the solenoid to the wiper door override switch.
Regards,
Alan
Drifting
Joined: Jul 2006
Posts: 1,259
Likes: 154
From: Deplorableville Nebraska
The issue here is when you pull the headlight switch the vacuum goes away in the complete control circuit. The culprit is the headlight switch, or how it is plumbed. If vacuum was only lost in the headlight control circuit, and not the wiper door circuit, this would not happen. You are losing vacuum in both circuits with the headlight switch.
The (very poorly designed) vacuum valve on top of the headlight switch is supposed to operate as follows;
1 - **** pushed in will allow the vacuum signal to pass through both vacuum ports, keeping control vacuum to the top of the actuator relays. This keeps the headlights down.
2 - **** pulled out vents vacuum at the front port from the control circuit which will move the relay piston, opening the headlights. The rear hose is blocked at the valve's rear port, allowing the control vacuum to remain in the other side of the control circuit (leading to the wiper door control circuit).
Doesn't really matter where the wiper door relay is located as long as it is operating properly.
The (very poorly designed) vacuum valve on top of the headlight switch is supposed to operate as follows;
1 - **** pushed in will allow the vacuum signal to pass through both vacuum ports, keeping control vacuum to the top of the actuator relays. This keeps the headlights down.
2 - **** pulled out vents vacuum at the front port from the control circuit which will move the relay piston, opening the headlights. The rear hose is blocked at the valve's rear port, allowing the control vacuum to remain in the other side of the control circuit (leading to the wiper door control circuit).
Doesn't really matter where the wiper door relay is located as long as it is operating properly.
Team Owner
Joined: Sep 2006
Posts: 31,198
Likes: 4,287
From: Westminster Maryland
Hi Dave,
"Doesn't really matter where the wiper door relay is located as long as it is operating properly."
I realize it doesn't matter WHERE the relay is mounted..... I asked D what year his car is in case he needed help in WHERE to look for it.
MANY folks don't realize it can be located behind the right side apron!!
Regards,
Alan
"Doesn't really matter where the wiper door relay is located as long as it is operating properly."
I realize it doesn't matter WHERE the relay is mounted..... I asked D what year his car is in case he needed help in WHERE to look for it.
MANY folks don't realize it can be located behind the right side apron!!
Regards,
Alan
Thread Starter
Drifting
Joined: Aug 1999
Posts: 1,451
Likes: 84
From: Round Rock TX
The wiper door opens when headlights come on and closes when they are turned off. The wiper door works fine with the wiper switch. The vacuum connections at the headlight switch appear to be correct. Today I did a few small things (fast idle adjustment) and the tried the overrides for wiper door and headlights. When pulling the override the wiper door opened with both, but not the headlights. I could keep the headlights up when pulled though. The opening of the wiper door seemed a bit slower, but could be my imagination.
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