C4 Interior Overview

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The C-4 interior is comprised mostly of plastic. The 1984-1989 dash carrier is made entirely of plastic. All of the plastic dash fascia can be damaged quite easily just by over-tightening the screws. I use a screwdriver or a clutch-operated power screwdriver. When using a clutch-operated screwdriver, be sure to use the lowest setting to avoid cracking the dash fascia. Then use a Phillip’s head screwdriver to check for tightness. A cordless drill with a Phillip’s head bit is a good idea for removal only; definitely use a screwdriver when tightening. Early cordless drills did not have any torque setting options. They require extreme care if used for any dash screw tightening.

The light switch area of the dash carrier typically cracks when this occurs a rattle or creaking noise will be heard that is difficult to locate. I repair these by fabricating a reinforcement plate using a piece of .020 gauge aluminum. The light switch stud nut and the dash carrier mounting 13mm stud nut must be removed to fabricate and install the reinforcement plate. The light switch shaft will have an outer nut holding the light switch to the dash, which will be referred to as the light switch stud nut. This can be removed with a special socket or a pair of snap ring pliers. A pair of needle nose pliers will work in a pinch. A paper file folder can be used to make a pattern- and save a lot of aluminum. A file folder is thicker than paper but cuts easily with scissors this will allow you to cut out the holes for the light switch stud nut and the dash carrier mounting stud. Make sure the reinforcement plate pattern covers the entire cracked area. Now transfer the pattern over to the aluminum plate. Then drill a 7/16” hole in the lower corner of the reinforcement plate for the light switch shaft. Next drill a 3/8” hole in the upper corner of the reinforcement plate for the dash mounting stud. I use a good quality epoxy to bond the reinforcement plate to the dash carrier. The reinforcement plate and dash carrier must be cleaned carefully and free of all oil. Isopropyl alcohol or automotive brake cleaner spray will remove any oily residue. After applying epoxy to the reinforcement plate I install it over the light switch shaft and dash carrier mounting stud. Tighten the dash carrier mounting nut. Install the light switch stud nut into the light switch. Then I like to put two 1/8” rivets in the reinforcement plate to keep it tight until the epoxy sets up avoid riveting in the cracked area. I have only seen one, possibly two cars that did not have a badly broken dash carrier, so look for this during a dash restoration.

Another common complaint would be rattling in the dash or console area. The early cars (before 1988) rode very rough and therefore were very tough on those plastic interior pieces. Loose screws and rough roads will wreak havoc on plastic interior components. Loose and missing screws can make things very noisy. Unfortunately, most of the C-4’s I have seen are missing quite a few screws- it does not matter if it is an ‘84 or a ‘96! I have seen a lot of 1984-1989 cars that have a screw in a hole, but there is no clip on the backside to hold the screw. I have also seen cars with no plastic tab to put the clip on. It is a good idea to check all the visible screws for tightness periodically. I have a policy that I always install all of the screws in every panel that I remove. Therefore I often install new screws and clips to make sure everything is tight.

Another trouble spot I have seen is the digital cluster. Very few of the 1984-1989 cars have all four of the 7-mm screws holding the digital cluster to the dash carrier. The 7-mm screws can be installed with a 7-mm socket on a 6” quarter-inch extension and a quarter-inch ratchet. I use a piece of black vinyl tape to wedge the 7-mm screw into the socket. This holds the screw for easier installation.

On 1984-1989 Corvettes, check the upper dash pad screws that go through the dash carrier then into the dash pad. Many of these screws are loose or missing. There are six screws across the underside of the dash pad. There are no screws on the passenger side where the crash protection cushion is. On the very outside of the passenger side dash pad there is one screw that is hidden under the fuse panel fascia. This is typically broken because it is not noticed if the dash pad is removed. These dash pad screws will create rattles if they are left loose. They may appear tight, but when moving the dash pad you will find that the pad is not tight to the dash carrier. The screws fit tightly in the dash pad and sometimes require extra effort to tighten properly.

The radio and A/C controls are located under the center dash fascia. There are 7-mm screws are used to retain the radio and A/C controls; these are often loose. The driver information center that is above the radio is held with 7-mm screws. The outer screws that go through the driver information panel must be carefully installed. They thread into a panel that moves easily out of place.

Replacing the passenger side crash protection cushion is often done on the 1984-1989 cars. Removing the cushion properly is difficult! The upper dash pad must be removed to access the upper 7-mm screws that retain the cushion. The dash pad screws that go through the dash carrier must be removed. The screws are installed in front of the digital cluster and center dash fascia. Removing the fuse panel fascia will allow you to see how things are put together. The fuse panel fascia is retained with Phillip’s head screws. Do not forget to remove the upper dash pad outer screw on 1984-1989 Corvettes. This screw is located behind the fuse panel fascia. Next the two screws that are in the dash pad defroster vents must be removed. These are Phillip’s head screws. I use a 24” long screwdriver to remove them. A regular length Phillip’s head screwdriver can be used although it is a little more difficult. Pick up on the center of the dash while pulling straight out. This will allow upper dash pad removal. Two aluminum brackets with screws at the top and bottom hold the crash protection cushion. These brackets are retained by one 7-mm screw at each corner. The lower crash protection cushion screws are very difficult to remove. The under dash trim panel must be removed on the passenger side to access the lower crash protection cushion screws. Remove the four 7-mm screws to remove the panel. Disconnect the footwell lamp by moving the connector side-to-side while pulling outward on the connector. The lower crash protection cushion screw on the outside can be seen through the opening at the fuse panel area. I use a 7-mm socket with two1/4” universals to negotiate the lower crash protection cushion screws. The lower crash protection cushion inside screw cannot be seen to remove it. After removing the other three screws I pull out on the crash protection cushion. Then, using a pair of pliers I hold on to the screw threads and loosen the screw. The screw can then typically be threaded out of the retainer clip. It is much easier to back the screw out of the retainer clip than trying to loosen it by the screw’s hex-head. I have also seen the lower part of the crash protection cushion brackets cut off. This makes removal simple but the crash protection cushion will require extra preparations if you want to reinstall it.

In the same area, if you plan on replacing the knee bolster carpet on the passenger side, having the crash protection cushion removed will allow easier access to the nuts that retain the knee bolster. It is not absolutely necessary to remove the knee bolster to replace the carpeting. It is a toss up though; is it easier to remove the knee bolster and install the carpeting or gluing the carpet to the knee bolster than tucking it into the dash area. Removing the knee bolster requires Engine Control Module (ECM) and ECM housing removal and as mentioned earlier, crash protection cushion removal. The knee bolster is retained with four 13-mm nuts. This requires patience, but knee bolster removal is the best way to replace the carpeting. The driver’s side knee bolster is much easier to remove. Remove the lower dash trim panel 7-mm screws. Originally there was a push-on retainer at the rear of the lower dash trim panel. This push-on retainer pushes on to a stud at the base of the steering column. By now I rarely see these retainers installed. The retainer can be removed by holding the retainer with pliers then pulling down while working it back and forth. The Phillip’s head screws in the knee bolster to dash trim must be removed.  The driver’s side knee bolster has four 13-mm bolts retaining it. These bolts are located in the carpeted area of the knee bolster. Remove the four 13-mm bolts, then the knee bolster. Removing the carpeting from the knee bolster can be difficult sometimes. A heat gun can simplify carpet removal. Remove the knee bolster carpeting by pulling back the carpet at any edge then apply heat while pulling the carpet off of the knee bolster. Be sure to use heat carefully. Heat can damage plastic panels, or if not enough heat is applied the foam can be ripped off the knee bolster while removing carpeting.

Console plate removal is not difficult. The shift knob must be removed. Automatic transmission equipped cars have a snap ring under the shift detent button. The shift detent button can be removed with two small screwdrivers. Use them to pry the button up carefully. Remove the snap ring with a pair of small snap ring pliers then pull the shift knob straight up. Manual transmission equipped cars have a shift knob lock that prevents the shift knob from turning. Remove the shift knob insignia plate with two screwdrivers prying plate upward. Once the insignia plate is removed you will find the lock at the six o’clock position. This lock can be removed by prying it up carefully. The shift knob leather can be damaged if care is not taken. Once the lock is removed the shift knob can be removed by rotating it counterclockwise.

On 1986-1988 4+3 transmission equipped cars, the 4+3 shift control button is integral with the shift knob. The back of the 4+3 shift button pivots on the shift knob. The 4+3 shift button is connected to a rod that controls the 4+3 switch. The 4+3 shift button must be unclipped from the rod then removed from the hinge point of shift knob. The shift button rod must be unscrewed counterclockwise. Then remove the shift knob lock in the same manner as the six-speed transmission, being careful not to damage the shift knob hinge points! Unscrew the shift knob counterclockwise. This will allow you to remove the shift plate. Usually there is quite a myriad of items under the console plate: coins, cigarette butts, pens, earrings, etc., so you may want to make this an annual event.

The 1990-1996 console shift plate has an additional 7-mm screw to remove in the center of the front cup holder. The 7-mm screws at the back of the 1990-1996 console shift plate are hidden under a piece of material. Pull back the material at the front edge of the console compartment to locate these screws. When reinstalling the console shift plate on automatic transmission equipped cars be sure to put the shift quadrant pointer on the pin of the shifter.

Check shifter quadrant operation before installing any screws. The 1984-1996 console compartment door requires that the compartment lamp wiring connector be disconnected. Sometimes the connector can be pulled out of the console side panel and then disconnected. Sometimes the connector will not come out of the console side panel. This will require removing the two passenger side console panel upper screws. These screws are under the console compartment door. After screw removal pull the passenger side console panel out just enough to allow the connector to be accessed for removal.

The seats must be removed to allow console side panel removal. The seat bottom cushion on all C-4’s must be removed to gain access to the seat-frame to seat-track 13-mm bolts. The bottom cushion has a wire bail that clips on at the front and center of plastic seat shell. A small regular bladed screwdriver works best when popping the bail off the seat shell. If equipped with sport seats, the lumbar bladder supply hoses must be carefully removed with a small bladed screwdriver, gently prying the connector apart. Then disconnect the electrical connectors. Once the seat cushions are out, the four 13-mm seat bolts can be removed. Remove the electrical sport seat control connectors on 1990-1996 cars before pulling out the seat. Now the seat track assembly can be removed. Remove the console side panels next. The console side panels have Phillip’s head screws retaining them in various locations. Look carefully in the carpeting at the ends and center for hidden screws. There are also 7-mm screws across the top of console side panels. 1990-1996 cars have screws at the top corner near the radio. The carpeting must be pulled away to locate these screws.

When removing the driver’s side console side panel, remember to remove the console compartment door latch lever. The console door lock assembly has a lever attached to it with a 5/16” screw. It requires a 5/16” wrench to remove.

The rear carpet replacement requires speaker grille removal. The side strips that are above the rear carpeting must be removed. The two front Phillip’s head screws that retain the shade clips are machine screws. Be careful to reinstall the machine screws in the same location. I have found it is best to use a Phillip’s head screwdriver to start the screws; these screws can be cross-threaded easily. The other three Phillip’s head screws in each strip are self-tapping

If you plan any sound system upgrade or after-market alarm installation, now is the time. It is much easier to do when the carpeting is out.

When installing carpet on the 1988-1996 doorsill panels, be sure to trial fit first before any cutting is done. Contact cement will hold the carpeting. Be careful to glue right to the edge of the sill or the carpeting will come loose. Glue the carpeting to the top of the sill first making sure that it fits tight into the rear corner.

Use care when removing the speaker grilles from the 1990-1996 sills. The studs can be broken easily. The studs go through the sill plate and then a self-cutting nut holds the grille to the sill. Therefore the sill must be removed first.

Rear shade removal requires an L-shaped tool to release the shade assembly. I use a bar 12” long with a 1-1/2” foot. After removing the rear window trim pieces the tool is used to pull the black plastic shade housing towards the center of the car. Pull the shade assembly outward while pulling the housing toward the center of shade assembly. Use care when using the release tool on the shade, if it slips off it can damage the shade. Most auto upholstery shops have the shade material available. It can be sewn on to your original shade roller assembly.

The door lock manual knob must be removed to remove door panels. The manual lock knob is clipped onto the manual lock rod. Use a screwdriver to pop the manual lock knob off. It is easier to remove the door panel if the manual lock rod is in the locked position. It is also a good idea to have the window down when working on the doors to prevent a lockout situation.

Door panel repair is possible- most of the factory panels I see are in good shape except for cracked substrates. I use the same technique to repair the door panels as I did the cracked dash. Most of the cracks in the door panel substrate are at the top. I use a piece of file folder to make a pattern. Follow the factory form of the upper section of the door panel using the upper door panel trim studs to reinforce the cracked area. Clean the area well with alcohol or brake cleaner. Then apply epoxy to the entire area. Install the reinforcement plate using the upper door panel trim studs to secure the top. I use C-clamps to hold the other side until the epoxy has cured. A 2×4, 15” long piece of wood is necessary to back up the C-clamp. Be sure to do this or the door panel vinyl will be damaged. Adding this reinforcement will help hold the door panel on the top of the door.

When replacing the upper door panel trim on 1984-1986 Corvettes, the original equipment door panels will need modification to fit properly. The replacement upper door trim has an additional reinforced stud. This reinforces the upper section of the door panel. This reinforced stud has an extra rib that will not allow the upper door trim to sit flat on the door panel. The door panel requires a slot cut in the stud area to accommodate the new upper door panel trim. If your upper door panel trim is good but the studs are broken off, I turn the self-threading nut over, then use a pair of pliers to install and tighten the nut. If there is not enough of the stud left to allow the nut to thread onto the stud the upper trim panel can attached with epoxy.

On some 1984-1989 cars, no matter what you do the door panel will come off the top of the door when the door is closed with even moderate force. On these cars I discuss with the owner putting an additional screw or screws in the top of the door panel to keep it in place.

When vinyl is pulling away from the door panel I have found that super glue is the only thing that will hold them together. So far we have been able to save most door panels with patience and careful application of adhesives.

When replacing sun visors, be careful of wire routing. It is easy to get the wiring in a pinch point especially around the removable roof bolt area. The sun visor pivot uses a spring, retainer, and 10-mm nut to hold them in place and keep them from rotating loosely. Remove the black plastic trim directly above the sun visor to access the 10-mm nut. The hardtop must be removed to remove the trim. After removing the nut the retainer maybe removed with two regular screwdrivers. Pry from side-to-side to remove the retainer. When installing the retainer I have found that a large pair of channel lock pliers works best. I protect the sun visor elbow with a cloth then I place a socket on top of the retainer and squeeze the retainer over the sun visor attaching pin. A C-clamp will work in place of the channel lock pliers. They like to slip though, so beware!

1984-1996 hardtop headliner replacement can be difficult. The headliner material is foam-backed cloth that is glued to a piece of fiberglass insulation. The fiberglass insulation should not be removed. Use care when working around the insulation. If you touch it with bare hands you will have raw fiberglass all over yourself. On the first headliner I repaired I used my fingertips to remove the foam. That was painful for a few days! After removing the original headliner material care must be taken when removing the foam that is left behind. Use a soft rag to rub slowly across the surface- this will ball the foam up. Then use a shop vacuum to remove the debris. A high power shop vacuum may remove more than the old foam. Try one area carefully with the vacuum before proceeding. Cut the material ½” larger than necessary. Apply 3M Super Trim Adhesive to the material and inside of the top. Apply the glue in a crosshatch pattern. After gluing down the material it must be carefully tucked under the outside edge of the top.

1990-1996 C-4 Interior

1990-1996 dashes have a couple of areas to be extra careful with. The center A/C register must be removed before the center dash fascia can be removed. Remove one 7-mm screw that retains upper part of center dash fascia. The center dash fascia also has push-in retainers- care must be taken when removing the fascia. Pull the center dash fascia out slowly while moving side-to-side.

The passenger side lower dash trim panel has a 7-mm screw behind the fuse panel fascia. Remove the fuse panel fascia and locate the 7-mm screw retaining the lower dash trim panel. Remove the 7-mm screw on the side and the screws across the bottom.

When installing the console door, pull up the door to the highest position, and then tighten the screws. This will prevent binding while opening. The console door foam can be torn away easily. Be careful opening the console door for the first time. If necessary, hold the console material tight against the hinge while opening. This will prevent damage to the console door if the door is adjusted too low.

When installing carpet on the 1990-1996 knee bolsters I find it easier to cut the carpeting from each screw hole area. This makes locating the screw holes easier when installing the trim panels.

The 1990-1996 door panels have a few hidden screws. There is a screw under the courtesy door lamp. Remove the door courtesy lamp by prying the bottom out with a small screwdriver. The screw is in the center of courtesy lamp area. There is also a screw under the manual door lock knob. Pop the manual door lock knob off the manual door lock linkage with a screwdriver. Locate the screw in the center of the manual lock knob area.

The 1990-1993 passenger door panel has a hidden screw under the window switch. The window switch can be removed with two small screwdrivers. Gently pry the switch out of the door panel. In the hole where the switch was should be a 7-mm screw. This screw goes into a bracket that is held with a screw to the door panel. Be sure to check this bracket before reinstalling the door panel. Many brackets are missing or loose. This is also a good indication if the door panel was removed previously. It is a good idea to put this screw back in place. You can capture the screw in a 7-mm socket with some masking tape or electrical tape. This makes installing the screw in the recess much easier.

The 1994-1996 passenger door panel does not use the hidden screw. Unfortunately all of these door panels seem to come off of the top of the door. To remedy this, I make a metal reinforcement out of .020 gauge 1” wide by 2” long steel. Bend the steel ninety degrees at ¾” from the end. This will allow an L-shaped reinforcement with 1 ¼” of steel on one end. Drill a ¼” hole in the center of the ¾” side of the reinforcement. The reinforcement will be installed on the top of door at the front area. There is a hole approximately 6” from the front of door that the reinforcement can be bolted to. This will prevent the top of the door panel from coming off the door.

When cleaning your 1986-1996 convertible, check the rear convertible top bow release cables under the rear deck lid for damage. Sometimes the cable retainer clamps are broken or loose. A cable that is hanging loose may get damaged when something is stored in the compartment. Also take a close look where the cable goes into the retainer at the end of cable. Sometimes they are ready to break. This can save the heartache of trying to locate the problem after everything has been latched.

Seat Covers

1984-1993 STANDARD SEATS

The standard seat cushions and backs are clipped into the fiberglass shell. They are the easiest to work with. The seat covers are held on the foam with hog rings. The outer perimeter hog rings must be removed, then the seat cover material pulled back to expose the inner hog rings. After removing all of the hog rings the seat cover can be removed. Place the new seat cover next to the old seat cover and note the position of the wire reinforcements in the original seat cover. I prefer to use a seat cover installation kit that comes with new hog rings and wire reinforcements. Install the reinforcements in the new seat cover then install on foam. The most common question is: Can I use the old seat foam? New foam will make for a better fitting cover and the seat cover will last longer. Most of foam I see is really bad by this time. Most of the Corvette interior suppliers have seat covers mounted on foam and the price is reasonable. Simply remove your seat cushions and backs and install the new pieces.

1984-1993 SPORT SEATS

These seats have a removable seat cushion but the seat back is integral with the seat shell. These seats require removal to install the seat back cushion covers. Also, the lumbar portions of the seat controls are in the seat cushion. The sport seat has a metal reinforcement in the seat cushion foam that must be installed in the new foam. The seat cover cushion replacement is similar to the standard seat cushion. The cover must be installed properly and then the switch cutouts must be carefully done.

The seat back consists of three pieces: the two outside bolsters and the inner cushion. The outside bolsters and inner cushion are held in with hog rings that run up and down the inner part of bolster. The outside part of the bolster is held with staples. It is stapled to the seat shell. All hog rings must be removed. Then the outer bolsters are removed by prying the outside edge off the seat shell. The inner cushion is clipped at the top to a retainer; this can be removed by pushing the seat cushion in on each side while pulling outward. The bottom of the cushion has hog rings that must be removed. They are accessed from the rear of the seat. Once all the hog rings are removed the cushion can be removed. There are three clear hoses connected to the lumbar support bladder that must be removed with the cushion. You will find that most seats do not have these hoses connected anymore because the bladders have turned to dust.

Quite a few of the sport seats have been converted to standard seats because the sport seats are not reliable. You can do this by deleting the lumbar control switches from the seat cushion and leaving everything else intact.

1994-1996

These seats require removal to install the seat back cushions. The seat cushions come out like the early cars. Covers are changed like standard seats.

Tips:

  • New foam and an installation kit should always be used.
  • Check seat cover material for defects before installing.
  • If installing new bladders, beware of any sharp objects or areas that may damage the bladder.
  • If the seat cushion supports are rusty or rotted on a 1984-1989 seat they can be replaced with an elastic strap and hook assembly. These straps were used on 1990 and up cars. The elastic material can be found at an upholstery shop. The hooks can be fabricated from 1/8” wire stock.
  • If you plan on restoring your sport seats to original specification, cut an “X” in the material where the seat switches go into the seat cushion. Do not remove any material from the “X,” this will prevent the material from pulling out on the sides. Tuck the material in carefully and then install the bezel. Use care when tightening the bezel; it can be cracked easily.

Story and photos courtesy Chris Petris

12 thoughts to “C4 Interior Overview”

  1. Is there a manual seat (as is installed in my 1986 C4 passenger position) available as a replacement for the electric sport seat currently installed in the drivers position? The drivers seat switches create a bumping sound, however no bladders inflate and the seat does not move at all. Can the passenger seat be installed in the drivers position directly or does it require modifications to fit the seat railings, etc.?

    1. You can replace your sport (power) seat rails with standard (manual) seat rails. The manual rails can be used on the Driver or Passenger side.

  2. I have replaced the radio in my ’84 with a “Retro Sound Newport” unit (non Bose). I have two factory mystery connectors that I can not find the other ends for, unrelated to the radio or climate control. The first one is a black connector with 4 wires: Two thick wires (orange, and purple) and two smaller wires (black, purple/black stripe). The second black connector has six wires (blk, tan, or, blk,gry,lt blue) and says “pack con” on the plug.

    I can’t see how they would have pulled loose, but my A/C won’t kick on anymore, ( the slider control is connected) and the “alert” that used to sound after shutting the car off has ceased. The alarm does still work though.

    Thanks for any help in advance!

  3. I have a problem with driver’s side power seat for 1989 vette. Seat moves okay in all directions, except can’t get seat moving forward. When trying, it has a vibrating buzzing sound, and will only move if I manually push. Can’t find any detail part drawing for power adjuster, etc. below seat.

    1. There may be a problem with the seat motor transmission jamming. Sometimes you can clean and lube them in place with positive results. Other times you must remove the assembly for service. You will need access below the seat cushion to service the power motor and transmission. Good luck with your challenge!

  4. Hello

    I have a 96 corvette, 30K, parked for the most part. My center vent has detached itself – the screws have nothing to grab as the inset it screws into busted. In 30 years of car ownership and rebuilding, this is a new one for me. How can the vent be reattached? Is it possible that the ABS plastic has “warped” putting outward pressure on the screws/inset and somehow ripped it loose? Oddest thing ever, no accidents, no other forces at work except normal driving.

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