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Tech Tips :: C1 & C2 Related Tech Tips :: Replacing the Power Window Motor in a 1993 C4

Information

Tools and materials

required:
Socket wrenches, drive, SAE and metric sockets, Phillips

and straight bladed screwdrivers, flashlight, needle-nose
pliers, torx
screwdrivers, electric drill and bits, 3/8 X 1
inch rivets or -20 X 1
inch stainless steel nuts and bolts,
grease, Loctite, RTV silicone, replacement
motor from Ecklers
($90 with S & H), 12 volt test light, electrical jumper
leads,
battery charger capable of 6 amps output, duct tape, and of course

the shop manual. Total time to actually replace the motor is approximately

5 hours the first time it is done.



Testing for a
defective
motor:
There is a detailed troubleshooting
procedure in the service
manual and I will not cover it in
this procedure, but will add a few tips.
Since it is a time
consuming process to disassemble the door to get at
the motor,
it is best to eliminate all other possibilities before replacing

the motor. Remember that when the manual refers to right hand or left

hand side of the car it is as you are sitting in the car. In other words,

an inoperative right hand window would be the passenger
window. This is
especially important when ordering a motor as
the right and left motors
carry a different part number.


size="2">Using the shop manual
and a 12 volt test light
determine if 12 volt power is at least getting
to the window
switch and the wires going to the window motor. The switch
can
be pried out of the door using a large flat-bladed screwdriver. It

is important to use a light rather then a voltmeter. The voltmeter can

show a voltage, but due to a poor connection it will not pass
current
and therefore operate the motor. If the light operates
you have power
up to that point. I wasn't sure where to get a
good ground connection
for one side of the test light so I ran
a lead out to the engine compartment
and connected it to some
metal on the engine.


I determined from
the wiring diagram in
the manual which two wires went directly to the
motor. I
disconnected the two connectors going to the window switch so

I would not blow any circuits in the car. I momentarily connected the

battery charger directly across the wires going to the motor. When the

window still didn't move I proceeded to take the door apart.
As a note,
I found a mistake in the color code of the wires in
my shop manual compared
to the actual color of the wires going
to the motor. I didn't determine
this until I had the door
apart.


size="2">Disassembling the
door:
Taking the door apart
and removing the window regulator took
me about one hour.
Start by disconnecting the negative terminal from the
battery
to protect the wiring. Remove the door trim panel as described

in the manual. There are sheet metal screws located along the bottom edge

of the door carpeting, in the door recess where you put your
fingers to
close the door, and several hidden screws. The
hidden screws are located
in the following places: One is
behind the slide that locks the door.
The door slide I'm
referring to is under the inside door handle. One screw
is
located inside the door and access is gained by removing the window

switch. Disconnect the two wiring connectors from the switch and lay it

aside. Using a flashlight locate the screw now visible through
the hole
where the switch was removed. If memory serves me
correctly, the screw
is about 1.5 inches long and is the only
one this size in the door. I
used a small plastic bucket to
place all the small parts I removed in
the process. There is
also one or two screws behind the courtesy lamp
bezel. The
bezel is pried out from the top. Carefully remove the bezel
so
as to not break it or the two lamps mounted inside it.



The manual says to

lower the window to remove the trim panel. I suppose this is
okay, but
cannot be accomplished when the window doesn't
work! Carefully remove
the trim panel from the door. If it
does not remove easily , check to
see if you have overlooked a
mounting screw.


Behind the trim panel
is a water
deflector. This is really nothing more then a sheet of dense

foam rubber. Use care when removing it as it could be easily torn. It

will be necessary to remove 4-6 plastic clips that hold the wiring harness

in place that run along the door. I used needle-nose pliers to
pry the
plastic clips out of the door. The water deflector is
held onto the door
with double-sided tape. Lay the water
deflector aside.


You can now see inside
the door and see
the window motor and regulator mechanism. It was at this
point
that I discovered the wiring color coding error. I again tested

the motor using the battery charger, as I could see the color of the wires

going to the motor. Since the window still didn't move, I
next removed
the metal accessory mounting plate. This is a
large piece of sheet metal
almost the size of the door that
various items are mounted onto. You have
to reach behind the
accessory mounting plate and disconnect the rods that
connect
the inside locking mechanism and also the inside door handle.

These rods are held in place by either a plastic or metal clip. Use care

that you don't break the mounting clips or the rods can fall
off of their
respective place after you re-assemble the door.
It was only necessary
to disconnect one end of each rod tin
order to remove the accessory mounting
plate. Remove all the
screws or bolts that hold the accessory mounting
plate to the
door. You have to twist the mounting plate inside the door
to
remove it. Once the mounting plate is out of the door you have access

to the window and window regulator.


face="Arial, Helvetica, sans-serif" size="2">Removing the window

regulator:
The manual recommends to mark the location of everything

you remove from this point on to aid in aligning the window
when putting
everything back together. Remove the window
stabilizer pads. Remove the
3 nuts that hold the window to the
regulator. Again this is best done
with the window in the down
position. At this point I removed the 4 torx
screws from the
cover of the motor. I now turned the motor armature with
my
fingers and lowered the window. It takes a lot of turning to lower

the window even a couple of inches. When the last nut is removed that

holds the window to the regulator, carefully lower the glass into the

door. Remove the mounting bolts that hold the window regulator in the

door. I had to play with the window regulator, turning the motor armature,

so that the window regulator mechanism would be as small as
possible to
remove it from the door. I still had to twist the
regulator assembly to
remove it from the door.



Removing the old

motor from the regulator:
The window regulator contains a
large flat
coil spring to aid the motor in lowering and
raising the glass. Use care
when removing the motor from the
regulator. I did not allow for the tension
on the spring and
found parts flying across the garage. The motor is fastened
to
the regulator with three 3/8 inch by 1 inch long rivets. Rivets are

used so that there is clearance for the window regulator gear to move.

I used a drill press to drill out all three rivets. Two rivets
were drilled
out from the regulator gear side of the motor and
the remaining one from
the motor side. I could not figure out
a way to remove the third rivet
without more disassembly of
the window regulator. (Replacement regulators
cost $200 from
Ecklers). I left the rivet that was directly behind the
window
gear in place and attached to the regulator. According to Ecklers

new rivets could be obtained for any Ace Hardware store. Yeah, right!

They only carried small aluminum pop-rivets. The rivets in the regulator

assembly appear to be made to steel and would have had to be
peaned over
after installation. Since one rivet was still in
the regulator assembly,
I used two -20 X 1 inch stainless
steel nuts and bolts to mount the re-built
motor. I had to
grind the head of one bolt so that it was very thin and
would
clear the operation of the regulator gear. I used Loctite on the

threads of these bolts. Removing the old motor and mounting the new one

took me 1 hour. My motor failure was due to moisture getting
into the
motor. My car had sat outside for 6 weeks for some
body repair, plus I
drove it several days in the rain going to
the NCM. One motor brush was
rusted in place and not making
contact with the armature. There is a rubber
gasket between
the motor halves. I coated the outside of the new motor
at
this joint with RTV silicone. I wanted some extra insurance against

water entering the new motor because of the amount of labor involved with

this repair, besides I wasn't able to drive my vette for 10
days from
the time I took it apart till it was back together.
After the regulator
is installed lubricate the window motor
gear with grease. Check to see
if any other moving part of the
regulator assembly requires additional
grease. I greased it
after it was mounted to prevent the grease from getting
on my
hands and then on my car's interior.


face="Arial, Helvetica, sans-serif" size="2">Aligning the window:

Aligning the window was not as difficult as I thought it would
be. I installed
the regulator and fastened the window to it. I
then used the battery charger
to raise and lower the window as
I made adjustments. The adjustment procedure
is in the shop
manual. I compared the contact of this window with the
rubber
molding of the door frame and targa top with the window on the

other door. When I re-installed the water deflector I used some duct tape

to hold it in place. Installing the regulator, window,
accessory panel,
and door trim panel took me 3 hours. Total
time for the entire job was
approximately 5 hours.


size="2">I figured I saved
approximately $225 in labor charges
and about $100 on the part. I also
made sure all the screws
and bolts were put back into the door, something
that does not
always happen when a someone else works on your car. .


 

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