C3 70 Wiper door

[Jim K.]

Well, I got all the little bits and peices installed from hoses, to actuators to relays and safety switches. When I try to get it all working, from wiper door opening through cycle, it just doesn't want to cooperate. I have the door off so I'm dealing with open space. Here's what's happening:
- Start the car - Door (linkage) open - wipers off.
- Turn on wipers, door closes - Wipers stay off (safety switch, o.k.) - play with the wiper switch off and on a few times and get the door (linkage) to open - wipers on, all is well
- Turn wipers off - wipers park - door (linkage) stays open
- Turn wipers back on - wiper door stays open - wipers work
- With Wipers on (and linkage open) manually press the wiper door safety switch (this is under the pass side wiper arm, and won't let the wiper door close unless the wipers are parked) the door (linkage) closes and the wipers stop mid wipe.
- Release the wiper safety switch and 3 seconds later the door (linkage) opens and the wipers resume.

I have tripple checked everything to the CC trouble shooting guide and a color schematic and it is all good. I think the control valve is the issue because somewhere during the above, I pulled the only small vacuum line off it and the door opened (I think) and I can manually pull a vacuum on it and the door closes, so I'm thinking vacuum leak on the control side. I tracked the lines through the firewall (all new just installed) and found that a small canister under the tach had an open port on it so I put a small length of hose and a plug in it but nothing (what is supposed to be there???). Should I bypass the bypass under the steering column?? If I can get the door (linkage) to open and close operating the safety switch during cycle, how come it won't close when I shut off the wiper??? Where is the electric to vacuum interface??? Anyone else home from work today too???
Thanks!!!
Jim

[george romano]

Re: C3 70 Wiper door

That hose you plugged on the switch behind the dash is supposed to vent. Take the plug off.

Pasta

[Jack H.]

Re: C3 70 Wiper door

George is right on... The vac circuit is this; you vent vac on the control side to cause the wiper door (HL's too) to open. That's done either by the electro-mechanical solenoid on the back of the tach or via the over-ride switch beneath the steering column. If either (or both) of these open and vent vac, that's the signal to open the wiper door.

On closing the wiper door, the RH wiper arm is supposed to contact the safety switch in the cowl when it parks. This is the signal to close the wiper door. The safety switch is mounted via enlongated holes allowing minor adjustment of switch relative to the parked/rest position of the wiper arm.

Also note one of the three hoses going through the rubber grommet at the firewall to the safety switch is cut and simply 'hangs in the breeze' inside the engine compartment. That's the safety switch vac vent line. It's routed into the engine compartment to thwart rain and airborne debris from entering the system (open end is protected by the hood). Often, you'll see this line 'plugged' by prior Bubba mechanics who didn't understand its function....

[Jim K.]

Re: C3 70 Wiper door

Thanks Jack and George (Pasta). I have that all straightened out and tried some additional testing including swapping the control circuit vacuum hoses under the dash at the headlight and wiper door by-passes. What happens here is that the wiper door works properly now with the headlight swithc and the headlight doors act like the wiper dood did. It seems that once I turn the wipers off there is some type of electric/vacuum swithc (maybe the thing on the back of the tach???) that won't let vacuum to the wiper door circuit to close the door once the wipers park. What other connection is there between electricity and vacuum (besides the light switch for the lights)? Any other thoughts? I have only addad the wiper astuator, wiper control module and the wiper park swithc and associated hoses (these were all missing when I got the car). The bypass and speedo can were there and I just replaced the hoses. Is there a test for the speedo can thing??? Lights still work fine... Thanks!!! This is starting to consume me!
Jim

[Jim K.]

Re: C3 70 Wiper door

I should clarify that while the wipers ar in motion, if I depress the wiper park safety switch, the wipers stop mid wipe and the door linkage closes, this is what leads me to question the electeic/vacuum switch...

[Jim K.]

Re: C3 70 Wiper door

OK here's the latest...
I bench tested the speedo solinoid (after checking that the wiring that feeds it is getting a constant 12v+/- when the wipers are on. There are three hose points from this solinoid one on one end tat is metal and two on the other end plastic. Of the plastic ones one has a hole what you would expext the inside of the tube to be, this comes off at 90 deg to the unit; the other plastic takeoff goes straight out but has a smaller than ID opening. Bench test has a strait through no restrictions between the metal and the 90 deg plastic with no connection to the small hole plastic; upon voltage across the terminals, the floe is inturupted but in pulses, not constant between metal and 90 plastic AND has same pulsing CONNECTION to the small plastic. That doesn't seem right.
Assuming I have the right connections going to it, I bybassed the solinoid and connected the two hoses together, this keeps the wiper door closed, when I disconnect this coupling the door opens and the wipers work; shut the wipers and the door closes once the wipers are parked (like it's supposed to do!).
I'm thinking that means the solinoid is bad??? In the meantime, I am connecting the two lines (by-passing the solinoid) with a tee and having a small hose and plug to manually operate the wiper door. Whaddya' think??? Jim

[george romano]

Re: C3 70 Wiper door

The switch behind the tach mearly converts an electrical signal from the wiper switch to a vacuum signal to the wiper door telling it to open. Thats all it does.
If you CUT vacuum to the white stripe signal hose (the small dia hose at the top of the relay valve) to the relay valve (either on the wiper door side or the headlight side) it will open the coresponding door. Thats the basic function of the pull down switches located under the steering column; they interrupt the vacuum signal to the relay valve and the door opens. The headlight switch does the same thing when you turn on the lights; vacuum is cut from the signal hose and the headlight doors open.
The diagram you used has a reputation for being inaccurate, although I have no firsthand knowledge of that.

Hope this helps some.

Pasta

[Jack H.]

Re: C3 70 Wiper door

On the tach mounted solenoid, there are three vac nipples. One nipple is the vac inlet (from the line through the firewall that comes off the check valve), the second is the vac outlet (feeds to/through the over ride switch), and the third is the vac vent (was originally covered with a square block of plastic foam that acted as a crude filter).

When the solenoid is de-engergized, the plunger blocks the vac vent. When it's engergized, the plunger moves and uncovers the vac vent. There should be no 'pulsing' action of the solenoid. It should be either open or closed...

If it's intermittently opening and closing on you bench, then you have a 'squirrely' electrical connection. Not all that unsusual as the solenoid winding wire is human hair thin and was orignally compression bonded to the electrical terminal (spade lug) on the solenoid.

If the the electrical terminal loosens and obtains any appreciable lateral movement (big Bubba hands inserting/removing the connecting wire), it's very easy to fatigue fracture the winding wire where it connects to the terminal. Then, you can either permanently open circuit the solenoid OR get a Jeckyl/Hyde situation where the wire makes contact, flows current for a while until it heats, bends and opens up.

You fix by visually examining the wire-to-contact junction (use a magnifying glass. And, if you see a break at the point of contact, clean the contact thoroughly, remove insulation for the remaining end of the solenoid winding wire (it's shellac coated, spritz a little paint remover on it to disolve the shellac and get to solid copper), and solder the winding wire to the solenoid's electrical spade lug connector.

Once you verify your electrical fix, mix up a little epoxy and laddle it onto the bottom of the spade lug (where it comes out of the solenoid) to restore its original rigidity. BINGO! You've repaired your original but damaged solenoid assy...

[Jim K.]

Re: C3 70 Wiper door

Thanks Jack, I'll give that a try before I lay out $75 (I think) on a new one. Back to the trhee connections, Which is which???
Thanks!
Jim