C4 power windows have gone through a few engineering changes from the agonizingly slow '84-'86 ribbon-lift windows to the later scissor-lift windows. The design stayed roughly the same except for the actual lifting device until 1994, when a front window guide was added to lessen window rattle and slop when the window was in any position. Previously, unless the window was fully open or closed at the limit stops, rattles occurred when you closed the door or were riding down the road. Nothing is foolproof, and the window-guide design proved to have a weakness-eventually the guide breaks, and the window has no upper limit stop at the front. The guide also doubles as the upper window limit travel stop. When the plastic-guide/upper-limit stop breaks, the window can become extremely out of position and, in some cases, glass breakage occurs. Corvette coupes get a double whammy as the glass can break, and the paint at the rear pillar gets scraped.
Nobody looks at the window for positioning before they close their door, unless they've noticed the window doesn't look quite right. If all of a sudden the window is too high at the front, most likely the stop is broken.
The task of fixing these issues is not too difficult, You can plan on spending a couple of hours removing the door panel and fighting the thread locking adhesive retaining the upper window stop to the glass. On the up side, the door panel can get a thorough cleaning while everything is apart. Our particular guide/upper-limit stop replacement Corvette had this issue for a while, but we recognized the problem and kept the window down a bit to compensate for the annoying problem. But enough enough's as they say, and it was time to rectify the situation.
Things You'll Need
- 3M black strip caulk
- KD trim pad removing tool
(PN 2822) - Window guide/stop LH
(PN 49549): $17.99 - Window guide/stop RH
(PN 49550): $17.99 - Whisper quiet door insulator LH
(PN 35469): $19.99 - Whisper quiet door insulator RH
(PN 35470): $19.99
Broken C4 window guides can...
Broken C4 window guides can cause lots of problems. Let's fix 'em!
1: Door-panel removal and...
1: Door-panel removal and replacement is similar whether you have an '84 or '96 C4. The manual door-lock knob must be removed by pulling the knob off the actuator rod. We use a hooked pick to pull it off carefully. The '90-'96 Corvettes have a screw hidden under the lock knob, while the '84-89 cars do not. Once the lock knob is removed, the screw can be accessed.
2: The '90-'96 Corvette courtesy...
2: The '90-'96 Corvette courtesy light also conceals another door-panel retaining screw. We're pushing the light back in here to remove the light assembly. We use a thin flat-bladed screwdriver to ease it out from the top. Pry gently at each upper corner with care as it's easy to break the flexible retaining tabs off.
3: The door-lock harness...
3: The door-lock harness connector fits tightly on the switch. pry it off carefully by slowly working it back and forth until it releases. Excessive force here can break the door panel plate. Also beware of using a metallic object, such as a screwdriver, to pry the connector off the switch. The terminals can be shorted together causing a blown courtesy fuse. There are two courtesy fuses located in the dash fuse panel; they are tagged right- and left-hand courtesy fuse if you happen to blow one during repairs.
4: Now we can remove the...
4: Now we can remove the lower door-panel plastic pushpins using our K-D Tools trim-remover tool. Push the tool all the way against the pushpins for support before working the pins side to side to release them from the door. Avoid putting the removal tool between the door panel and the pushpin since the panel can be scratched easily.
5: We need to remove the...
5: We need to remove the aluminum reinforcement panel next, so the rear upper-limit glass stop requires removal. The rear upper-limit stop has two 10mm screws holding it to the plate and is adjustable. You can mark around the large washer with a magic marker or use the witness marks on the plate to restore it to the correct location.
6: Here's an added twist...
6: Here's an added twist to the '94-'96 door reinforcement plate removal. A TORX head screw was added to the outside of the door panel for the door-lock actuator. Be sure to remove the screw before attempting to remove the panel.
7: The panel doesn't necessarily...
7: The panel doesn't necessarily need to come out fully, but the job is much easier if it's not fighting you the whole way. We usually disconnect the wires and push the plate down, then pull it out at the top. Once it's out at the top, it can be pulled up and let hang out of the way while you are doing the repairs.
8: Here's our broken guide/upper-limit...
8: Here's our broken guide/upper-limit stop ready for removal. There are three aggravating things to deal with here: a thread locker was used to keep it in place; plus a flat nut with two holes hold it from the backside; and if that wasn't enough, the piece is bolted through the glass. We use a pair of 90-degree snap-ring retaining pliers to hold the nut from the backside during removal.
9: Once the new guide is...
9: Once the new guide is installed, the problems should be solved. With any luck, this is what you'll see when you're done, not a pile of glass at the bottom of the door. If you had an unexplained side-window glass breakage, see if you can find the old guide/upper-limit stop. Most likely you will find it has been broken.
10: If necessary, these large...
10: If necessary, these large washer nuts adjust the window up and down on the regulator at the rear of the glass. Make minor adjustments and make sure to mark where the nuts were originally, especially if this is your first time adjusting the windows position. Once the guide/upper-limit stop is replaced, the window should be in the correct position.
11: Minor issues make big...
11: Minor issues make big statements. It bugs me to see the manual door-lock knob pulled away from the door panel, plus it rattles when it sticks way out. Here we're adjusting the door-lock rod to its correct position at the front. Almost every lock rod can use a little tweak to get it back where it belongs.
12: We're applying a bead...
12: We're applying a bead of 3M strip caulk to seal the insulation panel to the door frame. Using a new strip caulk ensures that the insulation panel will be in the correct position to do its job properly. The original strip caulk comes off easily with mineral spirits and a cloth.
13: Now we'll put the insulator...
13: Now we'll put the insulator in place starting at the center. Make sure you pull the manual lock rod and wiring through the insulator. Remember that the panel insulates the door from water, wind, and heat, so take your time and seal it well to the door frame.
14: We then reinstalled the...
14: We then reinstalled the door panel by reversing the steps of disassembly. This photo shows how to properly install the manual door-lock rod without damaging the rod. The small screwdriver is used to place the manual lock rod above the door-panel plate, allowing the rod to slip over and into the plate. If care isn't taken, the rod can be bent. Job done!