the wipers and wiper door stopped working on my 69 i i think it might be more than just 1 problem i've always had to use the switch below steering wheel to keep door open. i've had car painted and some starter work done i just put on new headers found small black wire with no end on it next to starter. seems like many, many years ago when we put the motor in this wire was a problem. it looks like a ground but goes to hot and if you wired it wrong it would run battery down. unless you pulled the duel connector on the wiper motor. i know this sounds crazy does this make any sense to anybody ? i just put new headers and sidepipes, marchpulleys,radiator hoses, aluminum waterpump and other goodies wife bet me a grand would never run again. she sits and reads directly behind car while i work. i plan 1st start up with no sidepipes or notice while shes reading

 

On my 71 ther is a ground wire that runs fron the wiper motor case down to where the heater blower motor picks up its ground. It would be on the passenger side near the starter. Maybe the connectore at the wiper motor is miswired. The ground wire on my 71 is a single spade connector separate from the 3 spade connetor that runs the wiper motor.
John
(edit) Try using a separte wire to ground the wiper motor case. The case has to be grounded for the wiper to work. Ground the case to the at unpainted area of the engine.


[Modified by theandies, 8:47 AM 4/13/2002]

 

:D :D :D :D :cool: :cool: :cheers: Man OH MAN, love that idea with the wifey-poo there..just LOVE it....now you gotta be sure you have your poopie together before you fire it, so it will start right up without any clues or cranking....snicker..... :D :D :D :D

blow her right OUTTA that chair!!!! snicker......

as to the ground wire, that black wire with the 3/8 loop on it, grounds both the wiper motor and the heater blower motor, and somehow some damn genius at GM wiring decided to put it to the starter bolt, instead of up top where in hell it belonged....so he spends 2' per car of extra wire, but scrimps on the gauge so you get voltage drop across it, as much as 1.5 volts when on high speed blower....so I upped the gauge to 10ga wire when redoing MY car....suggest you do the same....

It is way in hell beyond beyondo what in hell is on the minds of the GM wiring engineers....they slung sh it all OVER the sharks, the mid years weren't any picnic either.....I know, I just tore hell out of my harnesses last winter and spend bou-coups time rewiring the car to some sort of common sense, relocating grounds, heavying up wire gauge, rerouting harness to make common sense and ease repair/accessability...and relocating such obvious parts as relays, etc...

I mean that electrical department is as bad as the weatherstrip department...and thats saying something....

:mad :mad :mad :eek: :eek:

 

Here is a great expliantion of the entire wiper system that was posted here by Wayne Elwood, the Editor of Shark Quarterly (may it rest in peace! - What a great mag it was) (Wayne do you still hang around here????)

I think it's a "must have" for every early C3 owner....

------------------------------------------------------------

Understanding Your Windshield Wiper Circuit
(non-pulse only)
by: Larry Ingram

(Ghosted image of electric chart for
title page)

One of those seldom understood parts of the 68-82 Corvette is its wiper
system. This is particularly true of the 68-72 versions which had a unique
door system interconnected to the electrical circuit. If the vacuum part of
the door opening mechanism fails to open the door fully or the wipers don't
park properly, then the whole set up becomes very difficult to get back into
proper operation.

Since the Editor's "Project "68" needs this work as part of the restoration,
as well as the fact that the proper service manuals are hard to understand,
I thought our readers might like to have the benefit of an "improved" repair
guide.

Step one, as usual, will be to briefly describe each component as well as
it's function. Then I will describe the entire circuit in the simplest
language I can manage. I won't be able to cover every detail but I will give
you a solid grounding -- in more ways than one.

Wiper Switch - Most people expect the switch to be the power source but it
isn't. It simply grounds the wiper motor and / or the washer pump. If the
pump is wiper motor mounted it grounds a relay.

Wiper Motor - The motor is of a two-speed design using different field
windings to produce the two speeds. Incorporated inside the gear reduction
area of the motor is an electrical park relay and a small resistor. The
relay serves multiple duties and can be the source of most of the electrical
problems. Also as part of the motor (until about 77 or 78) was a mechanical
washer pump driven on demand, by the driver, by the motor's gear reduction
unit.

Park Relay - The park relay, when energized, allows the motor to turn. It
does this by simultaneously releasing its gear driven transmission and
closing a set of points which are concealed within its plastic housing.
(photo # 15 - optional as per space) This then allows battery power to the
field windings; this power keeps it running. Internally, the motor has a
field winding in series to its armature, as well as another winding called a
shunt. The shunt when energized limits RPM, causing the slow speed mode of
operation. The high speed current path is powered through the park relay's
points, through the field to the positive brush, and through the armature to
the negative brush, from that brush to ground, via an internal circuit
breaker. When the wiper switch is turned off the relay drops a hook (pawl)
into the path of the rotating reduction gear, stalling the movement as well
as pushing the points open to stop the motor.(photo #18) showing park pawl
assembly) Observing the rotation of the shaft where the linkage is attached
will show how the wiper arms get parked lower than in the normal sweep area.
The shaft parks in an offset path relative to where it is rotating during
normal operation. This is accomplished inside the gear mechanism by a slot
that controls shaft position.

Limit Switch - Used only on 1968-72 cars this switch controls main power to
the wiper motor, and is actuated by a linkage connected to the wiper door
opening mechanism. The switch is open (off) until the wiper door opens to
about 90% of its travel. Only if the wiper door is open should there be
power to the motor on this circuit.

Override Switch (1968-72 only) - Placed under the dash below the steering
column is a rotary switch as well as 2 vacuum switches. These switches allow
servicing the related components, since the wipers will park and be hidden
by the door even if the key is turned off, if not otherwise controlled by
the override switches. Many a frustrated owner has had the experience of
(apparently) failed wipers because someone turned the rotary switch to see
what it operated. If the wipers were off at that time no response was
noticed; but the first time wipers are demanded they won't work, if the
switch was left open.

Electrical Control Relay (1969-72 only) - A relay mounted inside the
console to the right of the radio, used to supply wiper switch information
to the motor circuit. The relay is needed to allow parking of the wipers
when the key is turned off.

Vacuum Circuit - 1968-72 cars featured a heavily advertised feature touting
the missing or concealed wiper blades, actuated by a vacuum circuit. The
vacuum circuit consisted of a large vacuum motor to open or close the door,
a vacuum relay used to send vacuum to the motor, an override switch under
the dash, an electrical solenoid behind the tach to send the vacuum signal
to the relay and an interlock vacuum switch moved by the right hand wiper
arm. Connecting all these parts are several feet of vacuum hose which can
rot, be pinched, knocked off, or simply connected incorrectly. Problems tend
to go un-noticed until the driver is caught in a downpour.

How Does This System Work

So, with these basic system components, the question now becomes, "How does
this system work?"

I will begin by describing the operation of the wiper door system. The door
is opened or closed on demand using engine vacuum, stored in a tank under
the left fender beside the master cylinder. The tank is evacuated (supplied
vacuum) by the running engine through a check valve and a filter. Vacuum is
directed as two separate circuits to the vacuum relay: one operates the
relay and one operates the vacuum motor (tank or double pie plate part
mounted above the heater on the firewall, just to the left of the hood
catch.) The relay is a spring loaded valve that can be pulled against the
spring using vacuum on a diaphragm. This causes it to direct vacuum from the
center port to one side of the vacuum motor while opening (ie: venting) the
motor's opposite side to atmosphere. Four hoses will attach to it, three
large and one small one (it's signal). (use photo # 4) When there is no
signal, engine vacuum is applied in at the large center nipple, routed
internally to the nipple farthest from the diaphragm end and via a hose to
the vacuum motor to open the wiper door via its linkage. When this happens
the top nipple is vented to very bottom of the relay where there should be a
foam filter in a square plastic framework. All of this is reversed if vacuum
is sent through the signal hose to pull the diaphragm up; the valve pulls up
opening the lower port to atmosphere and routing vacuum to the top nipple.

A vacuum signal is used to control the opening or closing of the wiper door.
This signal is applied to the relay's diaphragm to close the door, or the
signal gets blocked off and the diaphragm is vented to atmosphere to open
the wiper door. This job is done using a multiple switch path. The control
circuit consists of three switches in series, the interlock valve under the
wiper arm, the over-ride valve, and the solenoid valve. (photo # 20) This
solenoid is wired to the wiper switch and therefore whenever the switch is
turned on it is supplied a ground. The solenoid is live whenever the key is
on receiving its power through the wiper fuse.

Here Is How It Works

Vacuum is applied to the vacuum relay diaphragm. Engine vacuum goes to the
interlock valve via a hose. If it's depressed by the wiper arm, the vacuum
continues via another hose to both the underdash over-ride switch and vacuum
control solenoid. Either or both of these shut the vacuum off when
activated, and simultaneously vent the vacuum that was in the diaphragm thus
allowing the spring in the vacuum relay to switch vacuum to the opposite
side of the vacuum motor and open the wiper door. Remember that the relay
opens a vacuum path between two nipples and also vents the remaining nipple
to atmosphere; it does not just switch vacuum only. When the wipers or the
ignition is turned off, vacuum from the reserve tank will again be applied
through the interlock valve, after the electrics park the arms, through the
solenoid to the relay, unless the over-ride switch is pulled down. When the
vacuum pulls the relay's diaphragm and piston up, it directs vacuum to the
vacuum motor as well as venting the opposite side of the vacuum motor. It
would be difficult to pull the motor diaphragm if the opposite side was
sealed. Of course, if the override switch is pulled down the door will
remain open as the vacuum path to the relay diaphragm is blocked.

By using vacuum valves in this way GM engineers were able to prevent changes
in engine idle due to vacuum leakage below the carbs butterfly valves. If
the hoses get reversed at a switch or valve, then whenever it gets activated
a small vacuum leak is introduced and some change in idle should be noticed.

Now I Will Explain the Electrics

To begin, I will explain the basic set-up for the 1973 and later, and then
add in the extras used in 1968-72. Even though these latter years had
differences, there was a basic set of principles which applied.

As stated earlier, the wiper switch is only a ground source. The motor and
washer pump are supplied power on a yellow wire that is fused by the wiper
fuse & powered through the ignition key. If the key is on, then power is
supplied to one side of the park relay (hidden inside the area covered by
the washer pump or if the pump is under the jar then behind the cover over
the gear drive). The other two terminals of the motor control circuit are
wired as follows: terminal # 1 is used to create the high speed, while
terminal # 3 controls slow speed as well as the parking command, when the
wipers are switched off. These commands are received as follows, the wiper
switch grounds both # 1 and # 3 for low speed and only # 1 for high speed.
When the ground is provided the park relay magnetically pulls back the park
pawl, allowing the motor to rotate the gear reduction unit. Simultaneously,
a set of points inside the relay close allowing the power to the motor
field, armature and brushes which are all in series to each other, with one
brush being connected to ground via an internal circuit breaker. If the
points fail to close, are burned or pitted, or a brush is worn down or
simply hung up by rust or corrosion, then nothing happens other than the
pawl moving. IMPORTANT NOTE: Because the wiper motor is mounted to a
plastic body there is a ground wire attached to a terminal on the gear
cover. This can also get knocked off, corroded or it's other end
mis-installed. Whenever there is a problem begin by verifying the ground.
(Photo # 23 # 6 shows under dash override switch with pen pointing to
"vent to atmosphere" hole which is only visible with the override switch
pulled down in the "open" position - ie: to hold wiper door open)

1968 version - The circuit for 68 is unique and so far I have not found it
in any service manual so this information was arrived at the hard way, 1
wire at a time on a car that had been messed with. The motor in 68 is not
grounded conventionally. The ground brush is wired to the under dash rotary
switch. This prevents using any other year motor without making internal
changes. The park relay turns the motor on and off but the power to run the
motor comes through the wiper door actuated limit switch (live at all times,
fused at the horn relay by a fusible link ). This wire goes into the motor
and attaches to one side of the park relay point set, through the points,
field, brushes and armature and then back out of the motor into a harness
that takes it to the rotary switch, the other side of which is grounded
(switch closed). According to my notes there is a three-wire plug coming out
of the motor, red is power, brown goes to the vacuum solenoid on the back of
the tachometer (photo # 3 - optional for space), and a light blue which
changes to a black going to one side of the limit switch, through the switch
it changes to a brown, then to a brown with a white stripe, and ultimately
goes to the rotary switch. Each of the color changes takes place at terminal
plugs. Why it kept changing colors I don't know.

1969-72 version - To the best of my knowledge these years were all the same.
In 1969, an inside console relay was added, as well as grounding the
armature brush internally rather than via the rotary switch. The new circuit
put the rotary switch in series with the door actuated limit switch. This
means that power must flow through the switch and is easily checked with a
test light at a connector going into the motor (heavy red wire). The wiper
switch controlled the motor using the console mounted relay as follows.
Energizing the relay switches motor control to the wiper switch, closing a
set of points inside the relay case which grounds the motors # 3 terminal to
cause low speed operation. If the wiper switch is moved to high then both #
1 and # 3 terminals are grounded causing high speed. When the wiper switch
gets turned off, the relay looses it's power and the spring loaded point arm
opens completing another ground circuit. This grounds the # 3 terminal
allowing slow motor speed. Because the park relay lost its power when the
wipers were turned off, it has dropped its hook out to stop the gear in the
parked position, which (as it parks) will also open the field points within
the park relay. This stops the motor. Ultimately the wiper door will close
and disconnect the main feed by opening the contacts in the limit switch.

In this circuit set up the vacuum solenoid is wired in parallel to the
relay. Whenever the relay is energized so is the solenoid. The control relay
is wired, using 5 - 18 gauge wires, as follows:
- light blue, wired in parallel to the wiper motor # 1 terminal, the wiper
switch high speed terminal, and the vacuum solenoid;
- yellow, wired in parallel to the wiper motor # 2 terminal, the vacuum
solenoid, and the wiper fuse;
- light green, to the wiper motor # 3 terminal to provide the ground
necessary for low speed operation;
- black, to the wiper switch for low speed, connected by the relay when
energized;
- black /white stripe, to ground, this is connected to the light green if
the relay is not energized.

The wiper switch used for all years has three terminals, # 1 grounds the
washer pump when the switch is depressed, # 2 is for low speed, and # 3 for
high. In actual fact both # 2 and # 3 are connected to ground for low
speed. This translates to grounding # 1 and # 3 at the motor to get low, or
# 1 for high. For the years 1968-76 the wiper switch receives its ground
from the white metal dash cluster housing the gauges, later years had a
proper ground wire. Note: Many of these housings have been broken by
improper dash assembly causing intermittent operation. If your bezel is
broken at the sides just above the gauge area I suggest that you add a
ground wire directly to the switch. In some cases I, as well as others, have
received a substantial shock touching here during troubleshooting. I guess
the motor builds up like a coil looking for a path to ground.

So, that's it. A rough guide to the whole wiper/wiper door issue. When I
took on the assignment I thought I knew pretty well how the whole system
worked. Once I started looking at the service manual, however, I realized
how many important facts were left unstated and how badly the circuit
diagrams of the day explained the situation. I suspect that a lot of other
"guides" are equally poorly described, because this is a complex system. But
how are you going to fix it, if you don't know how it is supposed to work?
If you want to add any important points from your experiences, I welcome
your comments.
----------------------------------------------------------------------------------------

Hope it helps!!!

Mike

 

Mike69 - That is a great explanation...thanks. Do you have the original article form Shark Quarterly ?? I would like a copy of it because the explanation refers to some picture and you know what they say...a picture is worth a thousand words.
Thanks
John

 

Sorry John, I just saw your reply now... (I must have been asleep at the switch) No I dont have the actual article, sorry! :(

 

OMike69,
I highly compliment you on this excellent post.and hope that you are still active on this Forum.
I have had my 1970 since 1996 and never completely solved the problem of the wiper door opening up when the engine is shut off.
After replacing most all of the vacuum components including the vacuum tank, the source of the problem was the vacuum switch that is closed by the wiper arm going to home position. The switch had apparently been moved over time with many closing cycles to the point that it was not being actuated (closed). By moving the vacuum switch upward to the original position finally solved the problem.
This week, I had to replace the oil pressure gauge after which, the wiper door (to my surprose) is now Open after turning off the engine.
I do not know how i missed this post over the years with all my searching.
Two questions:
1. Do you have a suggestions as to what i may have done during this oil pressure replacement which included my taking out the right and center dash as well as the console.
2. When I printed the full thread, part of the text gets overprinted and is not totally readable. Of course no pictures are now included. Is it possible to get your full post including pictures.

Thanks again for your helpful post.

Looking forward to your early reply.

Jack
215-327-9556
jwhouse@comcast.net