Need some help diagnosing a windshield wiper problem
Thread Starter
Melting Slicks
Joined: Jul 2001
Posts: 2,609
Likes: 12
From: Massapequa Park NY
Need some help diagnosing a windshield wiper problem
Went through the tech paper on Willcox's website today. Found I was missing the ground at the wiper motor & fixed that 
Found I had a bad check valve & replaced that, now I have vacuum at the override switch. But still not working.
I have 12v at the red wire when the door is up and 0v when the door is down.
I can jump out the terminals with the connector removed at the wiper motor & get the motor to work
The wiper switch is grounded.
When I pull up the door & turn on the switch, I get 12v at terminal 2. I also have a ground at term 3 but the wipers don't turn on
If I reverse the connector at the wiper motor they turn on and will only turn off with the override switch
Have a separate vacuum issue as well, but have traced that one to far yet. If I pull down the override switch the door should open, but does not. With the switch up and the car started the door drops right away.
Help
Thanks
Jim
Found I had a bad check valve & replaced that, now I have vacuum at the override switch. But still not working.I have 12v at the red wire when the door is up and 0v when the door is down.
I can jump out the terminals with the connector removed at the wiper motor & get the motor to work
The wiper switch is grounded.
When I pull up the door & turn on the switch, I get 12v at terminal 2. I also have a ground at term 3 but the wipers don't turn on
If I reverse the connector at the wiper motor they turn on and will only turn off with the override switch
Have a separate vacuum issue as well, but have traced that one to far yet. If I pull down the override switch the door should open, but does not. With the switch up and the car started the door drops right away.
Help
Thanks
Jim
Safety Car
Joined: Jun 2004
Posts: 4,652
Likes: 80
From: Lakeland Florida
If you have a 1970 with the wiper door that opens, there is a small pneumatic switch that the passenger side wiper will rest on. This has 3 hoses that come off of it. Two of them are connected,and one will vent to air. The top of the switch seems to have some type of sensor that will indicate if the wipers are safe to operate, or if the wiper door is in the way. I think that is the function of this switch.
There is also a proximity switch at the front of the wiper door assembly near the wiper motor. This has a rod that goes through the firewall into the wiper area. It pulls the bracket into the switch or pushes it away to open the circuit. I think this also lets the wipers know if the door is open or closed.
kdf
There is also a proximity switch at the front of the wiper door assembly near the wiper motor. This has a rod that goes through the firewall into the wiper area. It pulls the bracket into the switch or pushes it away to open the circuit. I think this also lets the wipers know if the door is open or closed.
kdf
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,851
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
Found I had a bad check valve & replaced that,
Not sure what you mean by check valve.. Vacuum check valve at the intake?
now I have vacuum at the override switch.
Does the door open when you pull down the over-ride vacuum switch? Edit... answered that below... But are the hoses on in the correct position?
I have 12v at the red wire when the door is up and 0v when the door is down.
As you should.. The voltage to the motor is cut off and on by the limit switch that is pressed closed when the wiper door opens. This keeps the motor from running when the door is closed.
I can jump out the terminals with the connector removed at the wiper motor & get the motor to work
When you do this do you get both speeds and does the motor park? If so the motor is good.
When I pull up the door & turn on the switch, I get 12v at terminal 2. I also have a ground at term 3 but the wipers don't turn on
Verify your motor ground by running an extra ground or testing the existing one.
If I reverse the connector at the wiper motor they turn on and will only turn off with the override switch
Make sure the connector is on the motor as pictured in the help page and no other way. Make sure the wire colors are in the correct position.
When you do have the motor hooked up with the switch in the correct position.. doe you hear any noise when you try to turn it on
Have a separate vacuum issue as well, but have traced that one to far yet. If I pull down the override switch the door should open, but does not. With the switch up and the car started the door drops right away.
Check the hoses at the over-ride switch and make sure the one with vacuum is the one closest to the ****... if these are reversed that may be part of the problem.
The vacuum system is built so that when it fails it opens.. But.. go to the relay on the firewall and see if you have vacuum at the black with white stripe small hose... If so, great.. we move on.. if not then back track this hose to the wiper arm over-ride, then to the over-ride switch in the dash.. and see where the vacuum drops off. Something is hooked up vacuum hose wise... wrong!
But as you can see, everything has to be right for the system to work.
Not sure what you mean by check valve.. Vacuum check valve at the intake?
now I have vacuum at the override switch.
Does the door open when you pull down the over-ride vacuum switch? Edit... answered that below... But are the hoses on in the correct position?
I have 12v at the red wire when the door is up and 0v when the door is down.
As you should.. The voltage to the motor is cut off and on by the limit switch that is pressed closed when the wiper door opens. This keeps the motor from running when the door is closed.
I can jump out the terminals with the connector removed at the wiper motor & get the motor to work
When you do this do you get both speeds and does the motor park? If so the motor is good.
When I pull up the door & turn on the switch, I get 12v at terminal 2. I also have a ground at term 3 but the wipers don't turn on
Verify your motor ground by running an extra ground or testing the existing one.
If I reverse the connector at the wiper motor they turn on and will only turn off with the override switch
Make sure the connector is on the motor as pictured in the help page and no other way. Make sure the wire colors are in the correct position.
When you do have the motor hooked up with the switch in the correct position.. doe you hear any noise when you try to turn it on
Have a separate vacuum issue as well, but have traced that one to far yet. If I pull down the override switch the door should open, but does not. With the switch up and the car started the door drops right away.
Check the hoses at the over-ride switch and make sure the one with vacuum is the one closest to the ****... if these are reversed that may be part of the problem.
The vacuum system is built so that when it fails it opens.. But.. go to the relay on the firewall and see if you have vacuum at the black with white stripe small hose... If so, great.. we move on.. if not then back track this hose to the wiper arm over-ride, then to the over-ride switch in the dash.. and see where the vacuum drops off. Something is hooked up vacuum hose wise... wrong!
But as you can see, everything has to be right for the system to work.
Last edited by Willcox Corvette; Jul 17, 2012 at 09:56 PM.
Thread Starter
Melting Slicks
Joined: Jul 2001
Posts: 2,609
Likes: 12
From: Massapequa Park NY
Thanks for the help - I answered below
Jim
Jim
Found I had a bad check valve & replaced that,
Not sure what you mean by check valve.. Vacuum check valve at the intake?
Yes, that one which I really don't need since I converted to electric headlights & eliminated the tank.
now I have vacuum at the override switch.
Does the door open when you pull down the over-ride vacuum switch? Edit... answered that below... But are the hoses on in the correct position?
No, But I haven't had an opportunity to double check the hose routing. It does close on start up though if I leave it open
I have 12v at the red wire when the door is up and 0v when the door is down.
As you should.. The voltage to the motor is cut off and on by the limit switch that is pressed closed when the wiper door opens. This keeps the motor from running when the door is closed.
I can jump out the terminals with the connector removed at the wiper motor & get the motor to work
When you do this do you get both speeds and does the motor park? If so the motor is good.
Yes
When I pull up the door & turn on the switch, I get 12v at terminal 2. I also have a ground at term 3 but the wipers don't turn on
Verify your motor ground by running an extra ground or testing the existing one.
Was missing this one at first, fixed that & added a temporary ground, still nothing.
If I reverse the connector at the wiper motor they turn on and will only turn off with the override switch
Make sure the connector is on the motor as pictured in the help page and no other way. Make sure the wire colors are in the correct position.
When you do have the motor hooked up with the switch in the correct position.. doe you hear any noise when you try to turn it on
Verified the wires to your write up & compared them to two other cars last weekend, all good. I hear a click that sounds like it's coming from the wiper motor
Have a separate vacuum issue as well, but have traced that one to far yet. If I pull down the override switch the door should open, but does not. With the switch up and the car started the door drops right away.
Check the hoses at the over-ride switch and make sure the one with vacuum is the one closest to the ****... if these are reversed that may be part of the problem.
The vacuum system is built so that when it fails it opens.. But.. go to the relay on the firewall and see if you have vacuum at the black with white stripe small hose... If so, great.. we move on.. if not then back track this hose to the wiper arm over-ride, then to the over-ride switch in the dash.. and see where the vacuum drops off. Something is hooked up vacuum hose wise... wrong!
But as you can see, everything has to be right for the system to work.
I know - trying to separate the vacuum issue from the electrical problem. I open the door manually & can test electrically without the car running. At 95+ deg it gets hot really really fast with a big block running.
Not sure what you mean by check valve.. Vacuum check valve at the intake?
Yes, that one which I really don't need since I converted to electric headlights & eliminated the tank.
now I have vacuum at the override switch.
Does the door open when you pull down the over-ride vacuum switch? Edit... answered that below... But are the hoses on in the correct position?
No, But I haven't had an opportunity to double check the hose routing. It does close on start up though if I leave it open
I have 12v at the red wire when the door is up and 0v when the door is down.
As you should.. The voltage to the motor is cut off and on by the limit switch that is pressed closed when the wiper door opens. This keeps the motor from running when the door is closed.
I can jump out the terminals with the connector removed at the wiper motor & get the motor to work
When you do this do you get both speeds and does the motor park? If so the motor is good.
Yes
When I pull up the door & turn on the switch, I get 12v at terminal 2. I also have a ground at term 3 but the wipers don't turn on
Verify your motor ground by running an extra ground or testing the existing one.
Was missing this one at first, fixed that & added a temporary ground, still nothing.
If I reverse the connector at the wiper motor they turn on and will only turn off with the override switch
Make sure the connector is on the motor as pictured in the help page and no other way. Make sure the wire colors are in the correct position.
When you do have the motor hooked up with the switch in the correct position.. doe you hear any noise when you try to turn it on
Verified the wires to your write up & compared them to two other cars last weekend, all good. I hear a click that sounds like it's coming from the wiper motor
Have a separate vacuum issue as well, but have traced that one to far yet. If I pull down the override switch the door should open, but does not. With the switch up and the car started the door drops right away.
Check the hoses at the over-ride switch and make sure the one with vacuum is the one closest to the ****... if these are reversed that may be part of the problem.
The vacuum system is built so that when it fails it opens.. But.. go to the relay on the firewall and see if you have vacuum at the black with white stripe small hose... If so, great.. we move on.. if not then back track this hose to the wiper arm over-ride, then to the over-ride switch in the dash.. and see where the vacuum drops off. Something is hooked up vacuum hose wise... wrong!
But as you can see, everything has to be right for the system to work.
I know - trying to separate the vacuum issue from the electrical problem. I open the door manually & can test electrically without the car running. At 95+ deg it gets hot really really fast with a big block running.
Intermediate
Joined: Jul 2012
Posts: 33
Likes: 0
From: Tomball Texas
I will be buying a 1978 Corvette and I want to change out the old engine and 3 speed automatic. The 385 Fast Burn Crate Engine looks great and I want a 4 speed auto. The complete Crate engine may require some changes to radiator if I use the single bult system and I need help to find the right 4 speed automatic (700R4) and new linkage to allow me to use the 4 speeds. The crossmember may need to be changed. Can anyone send me any details to help me make the right shanges and where to but some of the needed parts?
Regards,
Rick Hawrylak
Regards,
Rick Hawrylak
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,851
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
I will be buying a 1978 Corvette and I want to change out the old engine and 3 speed automatic. The 385 Fast Burn Crate Engine looks great and I want a 4 speed auto. The complete Crate engine may require some changes to radiator if I use the single bult system and I need help to find the right 4 speed automatic (700R4) and new linkage to allow me to use the 4 speeds. The crossmember may need to be changed. Can anyone send me any details to help me make the right shanges and where to but some of the needed parts?
Regards,
Rick Hawrylak
Regards,
Rick Hawrylak
You should start a new thread on this.. I'm sure if you do someone will give you help.
Thread Starter
Melting Slicks
Joined: Jul 2001
Posts: 2,609
Likes: 12
From: Massapequa Park NY
Got half of it fixed
Picked up a new switch at Carlisle, for $15 in the swap meet , and now I have wipers. 
If I manually open the door that is
Now I just have to figure out what's not installed correctly in the vacuum system. Everything on that side is new, just haven't had time to play/diagnose yet.
Jim
, and now I have wipers. If I manually open the door that is Now I just have to figure out what's not installed correctly in the vacuum system. Everything on that side is new, just haven't had time to play/diagnose yet.
Jim
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Melting Slicks
Joined: May 2005
Posts: 2,209
Likes: 12
From: Montgomery Alabama
Cruise-In VII Veteran
St. Jude Donor '06