C-3 Wiper Door Issues

[Jacob A.]

Hello,

On my 69 the wiper door comes up only if I pull the plug on the can and stick a screw driver into the hole and press the rod toward the firewall. THe wipers won't come on on their own. Today I put the screwdriver in with the key on and the wipers in the "on" position. When the screwdriver hit the rod as far in as it could go, and the door was COMPLETELY open, the wipers come on and function fine (as long as I hold the screwdriver completely in, when I remove the screwdriver the wipers stop) What do you think is the problem?

Thanks,
Jacob
NCRS # 40987

[Rob M.]

Re: C-3 Wiper Door Issues

I've no answer to your question but I do want to complement on the attached picture!!! VERY NICE!!!

[Geoff C.]

most likely you need a wiper door actuator

test the vacuum on the front and back ports (i.e. the little metal pipes) to confirm

[Jim K.]

Re: C-3 Wiper Door Issues

Well there could be a number of things going on. To go backwards from just getting it all working but not properly, the electrical switch that the wiper door pushes against to complete the electrical circuit to the wipers is not getting pushed in enough; there is an adjustment for that in the form of a threaded rod and flat stop. if you increase the lenght of the rod, it will contact sooner and activate the wipers, just turn it out and lock the nut. The RIGHT way is more involved and could be the vacuum "motor" that actually opens the door (that you pull the plug on) ir the boot on the opposite side; or the "control" circuit and that diaphram device. From there it could be vacuum lines or the solonoid on the back of the tach. I would recommend (like many have recommended to me) the AIM for the car to see all the components and how they install AND the "Vacuum trouble shooter guide for headlights and wipers" that is sold by many of the vendors. There is some debate on who has the best package for this booklet, I think I got mine from Doc. Rebuild. And everything works now!!! Good luck!!!
Jim

[Clarence K.]

Re: C-3 Wiper Door Issues

Jaqcob,

You can check to see if the vacuum motor is working by connecting a hose to the front port of the motor. This is the port with the hose with the red stripe. You can blow on this hose and the door should open. If it opens, then suck on the hose and the door should close. You and do the same to the rear port(green stripe hose). If the motor works, you can trace the hoses to the vacuum switch. There are 4 hoses that connect to this. Red(front vacuum), Green(rear vacuum), Yellow(vacuum supply), and a smaller dia. hose that supplies vacuum to the switch.

In the default state with the engine running vacuum is supplied to the front port of the motor. You can disconnect the red hose from the front of the vacuum motor and you should have vacuum.

Parts are still available from corvette parts stores in
Wisconsin and Florida. If the vacuum motor is faulty and you are not going of have your '69 flighted, do not get the cannister type, these don't work(I know, i am out $155.00). Get the pie shaped, these work(another $125.00)

hope this helps,
gene#21147

[Dick W.]

Re: C-3 Wiper Door Issues

I do not understand why you say the coffee can vacuum cannister does not work. I have replaced several of them with like parts and they work fine. The pie pan works equally well, but not better than.

[Jacob A.]

Re: C-3 Wiper Door Issues

Thanks a bunch guys! I will try some of this out and get back to everyone.

[Terry B.]

Re: C-3 Wiper Door Issues

There could be one more thing to consider. It's not always a vacuum problem. On the early C-3's the bezel that holds the wiper switch is very fragile just above the radio and breaks on both sides. This is the metal bezel that gives the ground to the wiper switch. If the bezel is completely broken, the wiper canister will give the same symptoms as you describe. After replacing my actuator, replacing my wiper motor, and tearing the dash out looking for outer gremlins....it was only a bad ground on the broken bezel.

[Phil P.]

Re: C-3 Wiper Door Issues

72 lt1, all works fine until i turn off the wipers---the door closes too quickly and pinches the wiper arm---is it the switch that the pass side wiper arm comes in contact with ? does it need to be adjusted out some ? thanks for all and any input,phil

[Clarence K.]

[Jack H.]

Re: C-3 Wiper Door Issues

Typically, yes...wiper door closing too soon is a RH wiper arm to vac switch issue. Remove the grille and you have access to the vac switch.

You'll note that it bolts on via enlongated screw holes. Loosen the mounting screws and you gain up/down position adjustment of the switch. When the RH wiper arm contacts the top of the vac switch, that generates the vac instructions to start closing the wiper door.

If contact is made too early (before the RH wiper arm is essentially in its parked position), the wiper door with close and can pinch the wiper arm.

BTW, there's a full section in your copy of the Chassis Service Manual on the Corvette wiper system with a nice theory of operation discussion & adjustment tips!

[Jack H.]

Yep...

the first repro cannister type actuator we got for a customer job at our shop came with a note in the box warning NOT to attempt hand actuation...that it'd be WAY to stiff to actuate manually and would work A-OK with actual system vac pressure.

We installed it and it didn't work very well at all. A call to the mfgr brought up the question of whether or not our shop mechanics had tried to actuate the cannister manually. We admitted they had...

We bought a replacement cannister and this time around we simply gave it a 'test feel' instead of FORCING it through its travel path. Everyone doubted whether it would work, thinking we'd been 'had' by a poor reproduction part...

BUT, when we installed the fresh replacement part and let it do its thing under normal engine vac pressures, it WORKED LIKE A HOSE! So, the rule of thumb at the shop today is NOT to attempt a manual actuation of the repro cannister vac actuators because you can 'squirrel' them up using a bigger hammer approach to manually testing them.

[John H.]

Re: C-3 Wiper Door Issues

I have a additional wiper question. When I first start up my car 72. the
wiper door starts to rise up a little and then it returns to the down
position. What can I adjust to stop this movement. Every thing else works
in the wiper cycle as normal.
2. 2ND question is my water doesn't spray with wiper arms moving and wash
button pushed. The lines and bag have water. The lines also have been cleaned.
How do I know if pump is crapped out?
Big John, I have lost ops points to many times on this.....

[Terry M.]