cats22

So, here's my issue. I have a late '69 427/390. The wiper door works, as do the wipers, but not like they're supposed to by just sliding the main wipers **** on the instrument panel. Whenever I slide it from off to slow to fast, nothing happens. However, when I first pull the wiper door override switch under the steering column, the wiper door opens, and then the wipers work fine off the main ****. After sliding the main **** back to off, I have to manually push in the override switch to close the wiper door. Like I said, it all works, just not like it should.

I know enough to know that the vacuum and electrical systems here are intertwined, but not smart enough to figure out exactly where the problem is, or how to fix it. I'm thinking the problem is that the wires coming off the wiper motor/switch connector do not correctly feed into the vacuum system (where does that happen - at the Tach solenoid?) so the vacuum system never knows the wipers are trying to go.

I'd greatly appreciate any detailed input (with, hopefully) pics or a diagram that can walk me through solving this issue. The AIM is not very clear and the electrical diagram is Greek to me.

Many thanks in advance

Dave J

There are 2 ways to open the wiper door and complete the connected electrical switch to operate the wipers. You have obviously 1 that works (override) and 1 that does not. The wiper door solenoid is not working as it should (located behind the tach). The first test you should do is test to see if the solenoid is getting power, then you can test the vacuum path through it. To do the test, simply turn the ignition on, but do not start the car. Turn the wiper switch on, and listen for a CLICK behind the tach. Be sure to turn the ignition off when finished.

To vacuum test the solenoid, many pull it from the car. It is a pain to do. I have a method to test it in the car if you have a Mityvac or equivalent pump. Report back on the electrical test.

0Willcox Corvette

Illustration on where the tach solenoid is located. (in yellow)



Here is a vacuum chart to help you follow along.



As David has pointed out, the issue is more than likely the tach solenoid on the back of the tach.



When you turn the headlamp switch on, the relay gets a ground from the wiper switch and powers up. (the yellow wire is already hot) When this happens it blocks the vacuum to the wiper door operation relay shown below. By using the over-ride you're just replicating what the solenoid does.



When this happens the plunger drops in the relay and switches the vacuum to the up side on the larger hoses on the relay.


The solenoid gets power on the yellow and is waiting for a ground from the wiper switch.


If the solenoid is defective, you can not get an original one, they are on national back order. I do carry the replacement one and it works and functions perfectly. https://willcoxcorvette.com/corvette...solenoid-68-76

cats22

Thanks Dave.

I hear the click only when the wiper door is already open (by opening it with the override switch), and then the wipers start. I do not hear the click when the wiper door is closed (and, obviously, the wipers don't start).

But I noticed something in the vacuum set-up right above the override switch that looks wrong. Looks like Bubba may have been playing with stuff, and maybe why only the override works. The small red hose coming off the wiper arm safety switch looks fine; comes off directly into the override switch. But the small black hose coming from the check valve should T-bone, with one side a small yellow hose going into the solenoid and the other a small white hose going into the dash head lamp switch. Instead, I have two small black hoses off that T, one going directly into the override switch and the other presumably going to the head lamp switch (I can't tell exactly since it's so darn cramped under there and I'm upside down trying to push my head up into the pedals to see). I don't have that small yellow hose going from the T into the solenoid, nor a small blue hose coming from the solenoid into the override switch.

Also, how do you adjust how far down the wipers come? The top passenger side one is giving me problems. Yesterday it was fine; traveled far enough down for the wiper door to close over it. Today, not so much. It stops short and the wiper door doesnt close flush unless I physically push the wiper down first.

Many thanks again

0Willcox Corvette

It sounds to me as if someone has bypassed the solenoid... Possibly because they have been on back order so long and also possibly because they are a bear to get to.

You adjust the arms by following this procedure.

cats22

Much appreciate the blade diagram Willcox.

Should I even fool with the solenoid at this point? Does the clicking noise when the wiper door is open (but no clicking when the wiper is closed) signal to you guys that I have a functioning solenoid? I'd rather not go through the pain of properly configuring the vacuum hoses in those tight quarters, only to find out that the solenoid is toast. Maybe Bubba wasn't such a Bubba when he bypassed it ...

0Willcox Corvette

Double check the clicking noise, it may be the limit switch at the firewall... they tend to click when the door opens but no so loud when it shuts. Or it could be something else in the linkage.

If the click is under the dash then the solenoid may be working and just bypassed from the vacuum or maybe it was leaking and by-passed. Either way, if it clicks when you turn the wipers on it won't hurt a thing.


Getting to the solenoid is a royal pain... Another option would be to fish the yellow and blue wires out from under the dash and then mount a new solenoid somewhere else until you have a reason. All you would need to do is interrupt the vacuum hose before it hits the over-ride. Or you could do as you suggested and just live with it until you had a reason to go inside.

On the instructions above, don't forget to adjust screw A too.... that is the tweak that people forget about.

Willcox

cats22

OK, so this wiper adjustment thing has me all stumped. From what I can see, I can't adjust either wiper to go down further so the wiper door has enough clearance to close. Each of the blade assemblies fit into a slotted male connector head on the main assembly and the head doesn't seem to be adjustable up or down (at least not to me anyway). The main problem is the #1 blade (per Willcox's diagram above); it's pushed up hard against the wiper arm safety switch. But both could be lowered somewhat. My #2 blade sits beneath the #1 blade and it's still at least 2" above the stop.

In fact, adjusting Screw A to cover more of the top corners of the W/S made the problem even worse as it pulled the blade further up in its rest position.

First pic shows how high the rest position is of the #1 blade. Second pic shows how tight the #1 blade sits on that switch. 3rd pic is the slotted male connector on which each of the blade assemblies sit. 4th and 5th pics are the tops of each of of the male connectors.

Any input would be greatly appreciated.

Dave J

Have you tried removing the safety switch, and checking the wiper's travel? If the wipers sit down further with the switch removed, it can be adjusted lower beneath the wiper. The mount the switch attaches to has slots for the mounting bolts, allowing for the adjustment.

cats22

Many thanks Dave. Simple and easy advice. Slotted it down as far as possible, and it helped things out. Almost seems like the spring inside the switch is too long/strong, resisting the final inch or so of downward travel I need from that blade to clear the wiper door (until I push it down by hand).

Dave J

It is, that is just one of the things wrong with the Chinese safety valves. How old is your safety valve? Have you ever tested it?

cats22

Not sure how old it is; just bought the car (my first C3 ) last month and trying to knock out one project at a time. Cosmetically, it looks in pretty good shape so I cant imagine it's that old. Havent tested it yet; that's something that I'll need a quick tutorial on...

Dave J

Let me know when you are ready for the testing. Do you have access to a Mityvac or similar vacuum pump?

cats22

Right on, thx Dave! I picked up a Mityvac the other day. Gotta spend tonight cleaning up the other 2 projects I got going on, but will give you a shout in the next few days. Thx again...

cats22

Dave, just sent u a PM. Thx