COOLANT FAN SYSTEM DIAGNOSTICS SHOP MANUAL REVISION

VEHICLES AFFECTED: 1986 'A' SERIES EQUIPPED WITH LB6 ENGINE (2.8L V6 MFI VIN W)

The 1986 'A' series service manual may lead to unnecessary replacement of the air conditioning high pressure switch or electronic control module (ECM) as a result of inaccurate information on the coolant fan control system used in the LB6 2.8L V6 MFI engine (VIN W).

When diagnosing a customer comment of cooling fan running whenever ignition switch is in run, please note the A/C high pressure switch is a normally CLOSED switch. The 1986 'A' Service Manual incorrectly indicates that the A/C high pressure switch is a normally open switch.

The following schematic should be used when performing coolant fan system diagnostics. The attached schematic correctly indicates that the A/C high pressure switch is a normally closed switch which opens at 1930 kpa (280 psi).

NOTICE: CORRECT THE COOLANT FAN SCHEMATIC ON PAGE 8A-31-XX OF THE 1986 'A' SERVICE MANUAL TO AGREE WITH REVISED ATTACHED SCHEMATIC.

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.