1989 - 1991 Corvette: Service Bulletin: Proper Installation and Seating of the SIR Coil Assembly

Source: Chevrolet Service Bulletin
Bulletin Number: 91-204-3B - (01/23/1991)


The lower SIR coil assembly wires can be kinked near the shaft lock mechanism after service of the steering column. The improperly located wires interfere with the shaft lock and can be cut when the steering wheel is turned. The SIR coil must be reassembled correctly. During reassembly, do not force the coil down, and do not allow the lower coil wires to be trapped between the shaft lock and the coil assembly.


After the steering column has been serviced, the SIR coil assembly may be improperly seated with slack in the lower SIR coil wires in the shaft lock area.


The purpose of the following procedure is to eliminate slack in the lower SIR coil wires and avoid kinking of these wires in the shaft lock area. Proper installation and seating of the SIR coil assembly prevents the lower coil wires from being cut.

The following procedures may be performed with the steering column in the vehicle or as a bench procedure. If the steering column is not installed, position the column on the bench as it would appear in the vehicle. Refer to the vehicle service manual (Sections 3F, 3F4, and 3F5) for detailed repair procedures (See Figure 1).

NOTE: The SIR coil assembly is the last internal component to be installed in the steering column after service.

Begin this procedure with lower SIR coil wires routed through the column shift bowl exiting the I.P. bracket on the jacket assembly (wire protector removed) with the coil head hanging freely from the top of the column (See Figure 2).

Seat the SIR coil assembly as follows:

NOTE: SIR coil assemblies may be equipped with one or two sets of upper and lower coil wires depending on model.

1. Grasp the ends of all the lower SIR coil wires below the I.P. bracket (See Figure 3).

2. Grasp the SIR coil head with the other hand. Position the head assembly with the lower wires in the down position (See Figure 3).

3. Stretch the SIR coil head and lower wires so that they are straight and tight with no slack.

4. Pull on the lower wires to keep them straight while positioning the SIR coil head over the end of the upper steering shaft assembly.

5. Continue to pull on the lower coil wires while moving the coil head down on the steering shaft.

6. Align opening in SIR coil head with the horn tower.

7. Align the SIR coil "locating bump" between the two tabs in the steering column cover (See Figure 4).

8. Continue to pull down on the lower coil wires, keeping them straight with no slack, while seating the SIR coil head in the steering column.

9. Assemble the coil retaining ring.

10. Hold all wires straight and tight while installing the wire protector into the I.P. bracket on the bottom of the jacket assembly.

11. Refer to the vehicle service manual to complete reassembly and installation of the column. (See section 3F).

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.

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Article ID: 505
Created: July 25, 2014
Last Updated: July 25, 2014

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