Have a 72.

Wiper switch works
Wiper motor works
Wiper door works (goes up & down by using bypass)
Wiper arm lock (bypass) works.

Classic problem. Normal operation of car, turn wipers on by switch, they do not come on. If I manually open door using under dash release, door opens and then the switch will trigger the wipers on. If I turn them off, the wipers stop and go to "almost" the resting position. The passenger side wiper needs to be pushed down like an inch. Then I can manually close the door.

What in this scenario would be causing the switch to not allow the door to open normally (rather than bypass it). All the pieces to seem to work, but not like they should in sequence.

With respect the the 3 valve vacuum switch in the wiper bay on the passenger side, it's there, but I almost think that if the arm were able able to move another 1/4 inch, it might more accurately depress the button section.

Is this lack of full contact making the car think the door is open when it's not, therefore negating the opening function?

Or is there something else going on?


Thanks !

 

try this link for description of parts function, can you push down on the switch with a screwdriver thru the grill to verify your theory

http://willcoxcorvette.com/instructi...function_2.pdf

 

When you flip the wiper switch on the center console, you send electrical instructions to the vacuum relay (mounted on the rear of the tach) to open, vent vac, and cause the wiper door to open. The over-ride switch beneath the steering column is in series with this vac path. If either or both valves vent vac, the wiper door should open....

Common causes for the wiper switch failing to actuate the wiper door are:

(1) Your center cluster bezel is cracked and you have no ground reference for the wiper switch to the tach mounted vac relay.

(2) The tach mounted vac relay is defective or mounted improperly (no valid ground reference).

(3) Bubba has been under the dash and has the control side vac lines mis-routed. The sequence is from the engine compartment to/through the tach mounted wiper door relay, on to/through the over-ride switch, and back out through the firewall to the wiper door actuator.

 

Ok.. I can rule out (1). Need to validate (2) I'm thinking (3).
All the other sequences work except the most critical which is the turn switch, door opens wiper starts. I'm thinking 2 or 3 above since there is electric getting to the wipers... but the vacuum's not activated with with the wiper switch. Tach relay comes to mind. Probably time to trace the tubes...

 

Seeing as that the vacuum/lines T from engine into firewall and then go to the Tach Switch and then to the override, it would seem correct that if the override switch is working, there is vacuum in the line. since it's in circuit. I guess the question is where does the Solenoid take it's power from? I'm thinking the vacuum is working but the solenoid is just not engaging.

 

Hi ps,
Back to the wiper bay interlock switch.... if the wiper arm isn't all the way 'down' you can adjust the wiper linkage in the center (at the motor) to get it fully 'down'. If it's 'down', the wiper door 3 port interlock switch has some adjustment room in it's mount to move it closer to the arm,(2 bolts).
Good Luck!
Regards,
Alan

 

Good advice. I'll make the adjustment(s).

Maybe if adjusted properly, everything will work properly. What a concept. That's tomorrow's project.

 

The wipers will not come on if the wiper door isn't fully open, tripping the interlock switch on the firewall. If you open the door using the override under the column, wipers then come on, it's not your wiper switch or a cracked console. In that case the wipers still wouldn't come on.

What do you mean by "manually close the door"? If you are referring to closing using the override under the column, it's not likely to be the vacuum switch which the wiper arm presses. If this switch weren't fully pressed the wiper door would remain open.

If the wiper door operates as expected when using the override and the wipers go on when the door is open, door stays open until the wipers park, my guess is it's the solenoid behind the tach. Could be bad, could be the connector is loose or off, possibly wiring to the solenoid, maybe a vacuum hose problem.

Alan71 is right about adjusting the wiper position. Very easy to do with the grille off. I'd try that first just to see if things improve.

BTW: If the vacuum relays are original, they may be leaking a bit. I just replaced all three on my 70, vacuum switch under the wiper arm as well. The seals dry up when they get old. Probably not your primary problem but when they go bad the system gets a bit sluggish. When the door opens and closes, does it respond quickly or does it move rather sluggishly? Mine almost snaps shut after correcting several vacuum leaks.

 

So, when I say manually close the door, you're correct that I meant use the override. The manual action on the door is instant ... Telling me the vacuum is good. In looking at the diagrams, it seems that the vacuum lines go through the tach switch and then to the override. If that's right, then I'm thinking the vac lines are probably fine but the electrical part of the tach switch may not be working. Need to figure out if the on/off switch is in line with the tach switch since the on/off works once door is open and limit is tripped (if I press limit switch on firewall with door closed, the motor will try to lift wipers). Feels like on/off not causing tach solenoid to dump vac and open door....

 

Sounds like you're on the right track..

 

I'll take a look at this tomorrow and see if I can figure it out.. I'm sorry it's late tonight.

 

Great. thanks!

 

Classic problem. Normal operation of car, turn wipers on by switch, they do not come on. If I manually open door using under dash release, door opens and then the switch will trigger the wipers on.

So you are saying that if you pull the over-ride the wiper door opens and the wipers work...

If this is the case then the first thing i would check is the tach solenoid or the wires going to it.

For the wiper door to open you must block vacuum. The tach solenoid does this on H when you turn on the wiper switch. The over-ride does this on G when you pull it..

So.. on your car you have a yellow and blue wire.. yellow is the 12 volt wire and the wiper switch grounds out the blue one to make the solenoid block vacuum. See the picture below.. 15 and 16.

If I turn them off, the wipers stop and go to "almost" the resting position. The passenger side wiper needs to be pushed down like an inch. Then I can manually close the door.

This could be an entirely different issue and a adjustment. Lets solve the first question and then we shall move on.

 

Now to answer you question about the relay for the wiper door (F in the picture above). You must have vacuum on hose 10 for the door to close.. the default position on the relay is "Open"... in case there is an issue when everything is working right. The vacuum on hose 10 pulls the plunger in the relay and diverts the vacuum to the closed position.

Easy way to check the relay is to see if you have vacuum on 10.. and then pinch the hose shut with a pair of pliers and the door should open. I have to say you'll have vacuum on this hose.. since you said you use the over-ride and the door opens...

Willcox

 

It's Fixed !!!!!

Felt "compelled" to find the Wiper Tach Solenoid, test it, yank it, repair it .. whatever to get the wiper doors working. Was convinced this had to be the culprit.

Climbed under dash.. removed black plastic air vent piece. Loosened dash... dropped two bolts for steering column.... had my handy dandy telescoping mirror and a flashlight. FOUND IT. It's right there close to the radio side just tucked up in the most difficult to reach spot.

Pulled the dash pad forward a tad and what do I see ?

an empty flat spade connector and a black wire connector.
Reach up and feel around. Sure enough.. a second empty connector.
Quick study I am realizes that the thing is just unplugged.
NO WAY .. how easy is this?

But wait.. is it unplugged for a reason? Nah.. plug it it !!

Plugged it in. Crossed fingers. Started car. Hit button and BAM -- the wiper door opens. Will General Motors miracles never cease to exist.

Now -- as the wipers close, the driver's side closes first and then passenger side -- but they won't go that extra 1/2 inch, causing the door to hit. The door closes-- so I know the little vacuum release is good -- but can't seem to adjust the passenger side arm to get it to move down.

-- Tried moving the little vacuum switch thinking it was causing the arm to stop short. NOT.

--- Tried adjusting the two arm bolts in the center thinking there might be some play there. NOT.

-- I think these are not original arms which could be part of the problem , but perhaps there's some other adjustment? Oh -- can someone confirm that the driver's side blade is supposed close FIRST and then the passenger side ?


Thanks -

 

Hi PS,
The driver's side arm goes down first. If you think about it it HAS to since the signal to close the door comes from the passenger's side arm.
Have you tried adjusting the wiper interlock (G) so it's closer to the arm?
If you remove the passenger side arm and cycle the wiper motor through 'off', while pushing on the interlock plunger with your finger, does the door close?
Regards,
Alan

 

Alan,

Thank you for the insights... I was working on it.. read your confirmation on the driver's side and realized that the way to troubleshoot this was with the wiper arms in fully UP position. Loosened the two nuts on the passenger side and moved arm a bit...tightened..... repeated process ... adjusted passenger side... and

Ta-da !!

I can't believe I"m seeing it.. push the wiper switch, door opens, wipers appear and work... turn it off, they go into the channel and the door closes. Amazing.

Ok... I may buy a lottery ticket because I fixed a Hi-Speed Blower relay and the wiper doors in the same week.

Ignition key buzzer that won't stop is next !

 

Here is a picture of how to adjust the arms if you need it.

One other thing.. Some of the aftermarket blades being sold will not allow the arms to travel downward enough to clear the door. I had this issue on my 72.

Not relevant since you have fixed that issue but good info for those that read this thread later.