1977 Corvette: Service Bulletin: Anti-Theft Alarm Switch - Protective Grease
Subject: Anti-Theft Alarm Switch - Protective Grease
Model and Year: 1977 Corvette
Source: Chevrolet Technical Service Bulletin
Bulletin No: 77-T-57
Date: Oct., 1977
TO: ALL CHEVROLET DEALERS
Some 1977 Corvettes may experience inadvertent operation of the theft alarm because of electrolytic corrosion between the anti-theft switch (brass contactor ring) and left hand door lock assemblies. This corrosion can, in some cases, provide an electrical path to ground which sets off the anti-theft alarm.
Vehicles potentially affected by this problem are those produced between VIN’s 1Z37L7S427373 (the point at which the anti-theft switch was moved from the L.F. fender to the L.H. door lock) and 1Z37L7S441024 (application of grease to contactor ring in production).
Vehicles in the field affected by this condition can be corrected by application of a protective grease to the surface of the brass contactor ring portion of the switch as follows:
- Remove door lock cylinder and anti-theft switch from L.H. door per 1977 Passenger Car Service Manual pg. 2D-19 (See Figure 1).
- Separate the door lock cylinder from the anti-theft switch by removing the retaining ring which holds the two together.
- Apply a film of Packard Electric PM-771 grease to the surface of the brass contactor ring.
- Reassemble the anti-theft switch to the lock cylinder.
- Disconnect the theft switch harness connector from the door wiring harness connector and apply the same grease to connector pin areas. Reassemble connectors and apply this grease to the wire entry sides of the mated connectors.
- Reassemble the door lock cylinder and anti-theft switch to the L.H. door per Service Manual instructions.
A satisfactory substitute for Packard Electric PM-771 grease is GM P/N 1050109 or 1050110.