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Intalling a C4 Airbag Cutoff Switch
GM offers a kit to retrofit an airbag cutoff switch for Corvettes and here is how to install it.
Feb 8, 2005
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Intalling a C4 Airbag Cutoff Switch
Here are the items included in the kit: switch harness, stickers,rivets, switch mounting bracket, screws, display-lamp mounting bracket,and display-lamp harness. We couldn't wait to place the stickers on theswitch housing and display lamp. Not shown are the instruction bookletand the massive cable ties we didn't need to use.
Not shown in the previous picture is the CPA. No, not your friendly taxadviser. The small blue tab is a Connector Position Assurance retainerthat's clipped into the airbag switch-harness connectors. The airbagharness and wires consist of yellow-colored components, and the GMengineers really don't want this connection coming loose.
We didn't particularly care for the rivets that came in the kit. Becauseof where we're placing the switch, the rivets would not fit unless weplaced them upside down. We elected to use these 3/16-inch bolts andnuts with the integral star washers to attach the switch housing to theconsole floor.
Remove the shift button to expose the snap ring. You need to remove thesnap ring in order to remove the shift-handle knob. This is the mostdifficult part of the job, as you don't have lots of room to maneuverthe snap-ring pliers. Once the snap ring is removed, pull theshift-handle knob from the shaft. For the six-speed cars, there is nosnap ring. Instead, the knob unscrews, and there may be a set screw andinhibitor ring if your car is an early '94 or later.
In addition to the center console, compartment door, and centerinstrument-panel trim plate, both driver and passenger seats must beremoved. It may be a good idea to remove the top from the car at thispoint. The trim pieces under the front of the seats are retained withthese plugs. To remove, take a small slotted screwdriver and pull outthe inside tip as shown on the right. Remove these plugs and remove thetrim pieces to expose the two 13mm nuts holding down the front of theseats. There are two 13mm nuts holding down the rear also--the driverside has the wing nuts retaining the tire tool that must first beremoved. Move the seat fore and aft to clear the nuts for removal, thendisconnect the power-seat harness connectors under the seat and removethe seat from the car. If you have the sport seats with the power lumbarfeature, you have some extra items to disconnect. Once the seats areout, it's a good time to disconnect the battery to let the power bleedout of the airbag electrical components.
These speed nuts on the side of the center hump that help retain theside trim panels are designed for one-time use. You may have somedifficulty getting the cross-recess screw out if you've ever had workdone on your interior. One way to help with the reinstallation is toremove them and pound on the nut opening with a hammer. Another strategymay be to switch them left to right. And you thought speed nuts werejust another name for Corvette owners?
After removing the airbag fuses and letting the power drain out of theDiagnostic Energy Reserve Module (DERM), connect a ground wire for thedisplay lamp. We chose the lower bolt on the inboard side of theunderdash panel as shown here. We could snake the wire through thecenter dash, and the lower dash trim panel will cover it. Beware ofother bolts, as you may find one that screws into a plastic structuralmember. That won't serve as a good ground.
The airbag harness consists of yellow connectors. The driver side islocated outboard of the steering column. The passenger side, shown here,is located under the driver-side dash adjacent to the transmission hump.Locate the harness, remove its CPA, disconnect the harness, and plug inthe switch harness. Tie it all together with a CPA through each harnessconnector plug.
Snake the airbag switch harness through the hole you cut into theconsole floor tray and mount the switch using the bolts (instead of therivets that came in the kit). When locating the switch to drill themounting holes, temporarily reapply the console floor protector carpet.Trace around the switch and mounting bracket with a grease pencil. Thencut out this area so the carpet can be reapplied around the switchhousing and mounting bracket.
To provide power to the indicator lamp, locate an ignition feed circuit.These are usually pink wires, and there happens to be a pink wirerunning under the now-exposed console we can use for this purpose.Confirm that it's an ignition feed circuit using a test light: Probe thewire with the key on and key off. Key on should light, key off shouldnot. We prefer to solder the wire instead of using splice connectors.
Now reinstall the airbag fuses and test the airbag light on the driverinformation center display. It should still flash seven times when thekey is turned on, regardless of the switch position. As mentioned in theinstructions that come with the retrofit kit, it's a good idea toposition yourself well away from the airbag when first performing thistest (can you see the beads of sweat on my forehead?). If you'vefollowed the instructions in the kit, all should be fine. It's also agood idea to start the car at this point and let it run for a fewminutes to make sure nothing in the electronics has been inadvertentlydorked up--after all, you just performed minor outpatient surgery to asophisticated piece of electronics. We experienced a failure that mayhave been the result of flooding the engine after all the key-on/key-offactivity, but it runs fine now. It turned out to be a failed Opti-Sparkdistributor.
(above & right) Here's the completed installation showing the switch in the consolecompartment. Use your ignition key to set the switch. The switch is setup for the ignition keyway, but any GM ignition key for our late C4Corvettes (and other GM cars, for that matter) should operate theswitch; no locksmith is required. The spring loading is prettystrong--keep the torque on as you remove the key when setting the switchto the "off" position.
If you've had challenges getting the buttons on your electronic aircontrol to respond, give this a try: Remove the electronic air controlhead unit from the dash--it's retained with two 7mm screws. Unclip theharness connector and take the head unit to the bench for disassembly.Remove the six screws holding the unit together, and don't overlook theone hiding behind the foam grommet on the backside. Once the unit isdisassembled, take a clean eraser head to the pins of the control plateas shown. Using the eraser to clean the corrosion off these pins shouldresult in an electronic air control head unit that's more responsive toyour commands.
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