C3 Vacuum Issue
Thread Starter
Intermediate
Joined: Aug 2010
Posts: 43
Likes: 1
C3 Vacuum Issue
Had all new vacuum lines installed in my 70 rdstr when engine was rebuilt. Checked & rechecked routing against several drawings - Eckler's and ***'y Manual. Looks like all are correctly installed. But, when I start the engine headlight doors and wiper door open and won't close, except manually when engine is turned off. Also wipers do not operate.
What might be the cause? Could a bad check valve cause this? Or, or???
What might be the cause? Could a bad check valve cause this? Or, or???
Intermediate
Joined: Aug 2014
Posts: 45
Likes: 0
From: Southern NH
Had all new vacuum lines installed in my 70 rdstr when engine was rebuilt. Checked & rechecked routing against several drawings - Eckler's and ***'y Manual. Looks like all are correctly installed. But, when I start the engine headlight doors and wiper door open and won't close, except manually when engine is turned off. Also wipers do not operate.
What might be the cause? Could a bad check valve cause this? Or, or???
What might be the cause? Could a bad check valve cause this? Or, or???
Team Owner
Joined: Sep 2006
Posts: 31,170
Likes: 4,248
From: Westminster Maryland
Hi Bob,
Was there some problem that caused you to change the hoses?
Have you checked that the wiper door and headlight door over-ride switches are pushed up and the wiper motor stop switch is turned clock-wise?
Your problem is likely in the 'control' side of the system, so check the small hoses, relays, and safety switch.
Were the hoses under the dash changed too? Did you double check the headlight switch hoses…. blue striped to the front nipple and black hose to the rear?
Regards,
Alan
Was there some problem that caused you to change the hoses?
Have you checked that the wiper door and headlight door over-ride switches are pushed up and the wiper motor stop switch is turned clock-wise?
Your problem is likely in the 'control' side of the system, so check the small hoses, relays, and safety switch.
Were the hoses under the dash changed too? Did you double check the headlight switch hoses…. blue striped to the front nipple and black hose to the rear?
Regards,
Alan
Le Mans Master
Joined: Jul 2006
Posts: 8,117
Likes: 104
From: charlotte north carolina
As Alan posted, since both the wiper and headlight doors open, the problem is in the control circuit. these systems were designed so that a loss of vacuum (either intentional by way of a switch, or unintentional by way of a failure) will open the door. It sounds like you have lost the vacuum on the entire control side of the system.
Melting Slicks
Joined: Mar 2008
Posts: 2,023
Likes: 6
From: Austin Tx
I agree with the above, first make sure both the overrides are not pulled.
But, if that's not the case, and since both the wiper and headlight control circuits are not getting vacuum, I would think it should be very easy to find. The control circuit vacuum comes out of the 2 port check valve, and goes through the firewall, there it's split between the headlight switch, and the wiper door solenoid. I would think 1) you don't have vacuum coming out of the valve, or 2) the tee connection under the dash has come undone (do you hear a hissing sound under the dash?), or 3) the line from valve to tee is being pinched somehow.
But, if that's not the case, and since both the wiper and headlight control circuits are not getting vacuum, I would think it should be very easy to find. The control circuit vacuum comes out of the 2 port check valve, and goes through the firewall, there it's split between the headlight switch, and the wiper door solenoid. I would think 1) you don't have vacuum coming out of the valve, or 2) the tee connection under the dash has come undone (do you hear a hissing sound under the dash?), or 3) the line from valve to tee is being pinched somehow.
Thread Starter
Intermediate
Joined: Aug 2010
Posts: 43
Likes: 1
Hi Bob,
Was there some problem that caused you to change the hoses?
Have you checked that the wiper door and headlight door over-ride switches are pushed up and the wiper motor stop switch is turned clock-wise?
Your problem is likely in the 'control' side of the system, so check the small hoses, relays, and safety switch.
Were the hoses under the dash changed too? Did you double check the headlight switch hoses…. blue striped to the front nipple and black hose to the rear?
Regards,
Alan
Was there some problem that caused you to change the hoses?
Have you checked that the wiper door and headlight door over-ride switches are pushed up and the wiper motor stop switch is turned clock-wise?
Your problem is likely in the 'control' side of the system, so check the small hoses, relays, and safety switch.
Were the hoses under the dash changed too? Did you double check the headlight switch hoses…. blue striped to the front nipple and black hose to the rear?
Regards,
Alan
Bob C.
Thread Starter
Intermediate
Joined: Aug 2010
Posts: 43
Likes: 1
I agree with the above, first make sure both the overrides are not pulled.
But, if that's not the case, and since both the wiper and headlight control circuits are not getting vacuum, I would think it should be very easy to find. The control circuit vacuum comes out of the 2 port check valve, and goes through the firewall, there it's split between the headlight switch, and the wiper door solenoid. I would think 1) you don't have vacuum coming out of the valve, or 2) the tee connection under the dash has come undone (do you hear a hissing sound under the dash?), or 3) the line from valve to tee is being pinched somehow.
But, if that's not the case, and since both the wiper and headlight control circuits are not getting vacuum, I would think it should be very easy to find. The control circuit vacuum comes out of the 2 port check valve, and goes through the firewall, there it's split between the headlight switch, and the wiper door solenoid. I would think 1) you don't have vacuum coming out of the valve, or 2) the tee connection under the dash has come undone (do you hear a hissing sound under the dash?), or 3) the line from valve to tee is being pinched somehow.
Cheers,
Bob C.
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