Wiper door vacuum troubleshooting
Thread Starter
Drifting
Joined: Aug 1999
Posts: 1,451
Likes: 84
From: Round Rock TX
Wiper door vacuum troubleshooting
I am resurrecting a 70 LS5 that's been sitting for over 20 years. Got it fired for first time last week, and the wiper door didn't go down. We manually opened on of the headlights before firing it, and it went down after the car started.
Today I was able to lower the door with a handheld vacuum pump, so the canister is good. I fired the car and pulled the switch under the dash and the door opened slowly. The headlights did same slow open and close. I'm not sure if the issue is the part on Bach of the tach, the canister on drivers side of firewall, or whatever is in the wiper tray.
Today I was able to lower the door with a handheld vacuum pump, so the canister is good. I fired the car and pulled the switch under the dash and the door opened slowly. The headlights did same slow open and close. I'm not sure if the issue is the part on Bach of the tach, the canister on drivers side of firewall, or whatever is in the wiper tray.
Le Mans Master
Joined: Oct 2006
Posts: 7,123
Likes: 433
From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
After 20 years, any number of vacuum lines could be rotted/chewed/leaking. Even the vacuum tank could be rusted thru. I think I'd start by disconnecting the engine supply and pulling vacuum on that line. Test the whole system. If it won't pull a vacuum from there. start capping off systems one at a time until it does. Even the HVAC system could be the one holding up the show.
Team Owner
Joined: Sep 2006
Posts: 31,280
Likes: 4,372
From: Westminster Maryland
Hi D,
I would suggest that you order the Vacuum Systems Troubleshooting Guide from Dr.R.
Using your vacuum pump the guide will explain how to test each one of the component's function individually.
You may well find it useful in the future too.
I find that a hand held vacuum pump doesn't really supply enough vacuum to operate the system… things will work but slowly.
You really need to get to a point where you can use the engine as a vacuum source to know for sure just how well the doors open and close.
Good luck!
Regards,
Alan
I would suggest that you order the Vacuum Systems Troubleshooting Guide from Dr.R.
Using your vacuum pump the guide will explain how to test each one of the component's function individually.
You may well find it useful in the future too.
I find that a hand held vacuum pump doesn't really supply enough vacuum to operate the system… things will work but slowly.
You really need to get to a point where you can use the engine as a vacuum source to know for sure just how well the doors open and close.
Good luck!
Regards,
Alan
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,853
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
You used the vacuum pump to pull the door open did you check for vacuum on the wiper actuator relay. The relay controls what the actuator does and should have vacuum on the small hose to close and no vacuum on the small hose to open. So go to the relay and see if it's working first.... then I'd start working backwards from there going to the wiper arm vacuum switch and then to the over-ride and then to the solenoid.
The tach solenoid when energized cuts vacuum off from the system and makes the small hose side lose vacuum (same as the over-ride switch under the dash). So when you turn on the wipers the solenoid blocks the vacuum on the blue hose at the over-ride switch. So to check operation, pull the hose off the over-ride with the wipers off you should have vacuum on the blue hose and it should drop off when you turn on the wipers.
The video below on the wiper arm vacuum switch is the only one out there that properly test this switch. There is another one out there but it doesn't test from the correct nipple, this switch must be tested from the center port not the lower port.
Willcox
69-72 Wiper Arm Vacuum Relay testing.
1969-1972 Corvette Wiper Arm Vacuum Switch Test
The tach solenoid when energized cuts vacuum off from the system and makes the small hose side lose vacuum (same as the over-ride switch under the dash). So when you turn on the wipers the solenoid blocks the vacuum on the blue hose at the over-ride switch. So to check operation, pull the hose off the over-ride with the wipers off you should have vacuum on the blue hose and it should drop off when you turn on the wipers.
The video below on the wiper arm vacuum switch is the only one out there that properly test this switch. There is another one out there but it doesn't test from the correct nipple, this switch must be tested from the center port not the lower port.
Willcox
69-72 Wiper Arm Vacuum Relay testing.
1969-1972 Corvette Wiper Arm Vacuum Switch Test
Thread Starter
Drifting
Joined: Aug 1999
Posts: 1,451
Likes: 84
From: Round Rock TX
Things appear in good shape. The car was stored in a climate controlled garage for the past 20 years. Got the engine installed before Christmas, And broke it in last week. Still need to make tweaks to carb mixture, choke, and timing. Things were only ball parked to break it in. That is when I noticed the door didn't go down. I was able to open/close headlight and wiper door with override switches. I haven't tried turning on the lights, wipers, fan, or radio as main thing is to get it to run. I am not sure the cam specs since the previous owner installed it, and know that it's a little hotter than stock. Not sure if it will generate the vacuum needed to run the systems, as a result. I suspect it will though, having known the previous owner for such a long time. I have the boots that go on the headlight actuators and not sure if I have wiper door. He was going to restore it, but lost interest. I'm wanting to make it a driver, and not so nice that it is a trailer queen.
I was debating about putting an electric vacuum pump on the system to see if it operates, but would be better to test individually.
I was debating about putting an electric vacuum pump on the system to see if it operates, but would be better to test individually.
Team Owner
Joined: Sep 2006
Posts: 31,280
Likes: 4,372
From: Westminster Maryland
Hi D,
"Things appear in good shape. The car was stored in a climate controlled garage for the past 20 years."
It really varies from car to car as to how much work it might take to get both systems working properly.
I certainly wouldn't replace the hoses. If any thing, snip about 3/8" off each end of each hose. This gives the hose a new surface to seal to the nipple it's attached to.
Good Luck!
Regards,
Alan
"Things appear in good shape. The car was stored in a climate controlled garage for the past 20 years."
It really varies from car to car as to how much work it might take to get both systems working properly.
I certainly wouldn't replace the hoses. If any thing, snip about 3/8" off each end of each hose. This gives the hose a new surface to seal to the nipple it's attached to.
Good Luck!
Regards,
Alan
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,853
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
Things appear in good shape. The car was stored in a climate controlled garage for the past 20 years. Got the engine installed before Christmas, And broke it in last week. Still need to make tweaks to carb mixture, choke, and timing. Things were only ball parked to break it in. That is when I noticed the door didn't go down. I was able to open/close headlight and wiper door with override switches. I haven't tried turning on the lights, wipers, fan, or radio as main thing is to get it to run. I am not sure the cam specs since the previous owner installed it, and know that it's a little hotter than stock. Not sure if it will generate the vacuum needed to run the systems, as a result. I suspect it will though, having known the previous owner for such a long time. I have the boots that go on the headlight actuators and not sure if I have wiper door. He was going to restore it, but lost interest. I'm wanting to make it a driver, and not so nice that it is a trailer queen.
I was debating about putting an electric vacuum pump on the system to see if it operates, but would be better to test individually.
I was debating about putting an electric vacuum pump on the system to see if it operates, but would be better to test individually.
Alan is correct too, it's smarter to just snip off a bit from the hoses to eliminate them as the issue vs replacing all the hoses.
Willcox
Thread Starter
Drifting
Joined: Aug 1999
Posts: 1,451
Likes: 84
From: Round Rock TX
I have a new vacuum hose kit, well from mid 1990s but not used, thatbif needed can use. I would rather go the trim route if needed. Trying to be somewhat methodical about things. I likely will have to replace the cone thing in headlight canisters, and may end up on wiper door canister. It could be an issue where the door didn't close due to switch not working or other issue. Without doing a full system check, hard to say where issue is.
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Drifting
Joined: Nov 2016
Posts: 1,964
Likes: 579
From: Pittsburgh PA
just some food for thought. I went thru the basically the same thing.
bringing back a 68 that sat in a garage since 1986. When i started the car the wiper door would immediately open and not close. then suddenly one day i bumped the vacuum hose going to the canister and it closed and worked fine from that point on.
one item I did find- apparently the vacuum system is designed if it sees low vacuum the wiper door opens(safety feature). on my car it turned out the headlight actuator shaft seals were dried out. I replaced those and everything works as it should.
for me trouble shooting I just started isolating everything and testing with either a vacuum pump or the engine running. I blocked the lights at the "T" neat the brake booster to isolate the wipers and vacuum storage tank. and alan is right a handheld pump will not produce enough vacuum for the entire system. you have to isolate individual components
bringing back a 68 that sat in a garage since 1986. When i started the car the wiper door would immediately open and not close. then suddenly one day i bumped the vacuum hose going to the canister and it closed and worked fine from that point on.
one item I did find- apparently the vacuum system is designed if it sees low vacuum the wiper door opens(safety feature). on my car it turned out the headlight actuator shaft seals were dried out. I replaced those and everything works as it should.
for me trouble shooting I just started isolating everything and testing with either a vacuum pump or the engine running. I blocked the lights at the "T" neat the brake booster to isolate the wipers and vacuum storage tank. and alan is right a handheld pump will not produce enough vacuum for the entire system. you have to isolate individual components