Coolant Fan - Correct A/C High Pressure Switch Operation

Number 86-8-21 Date 11/86

Subject: COOLANT FAN SYSTEM DIAGNOSTICS


1986 6000 MODELS EQUIPPED WITH LB6 ENGINE (2.8L V6 MFI VIN W)

COOLANT FAN SYSTEM:

The 1986 6000 Service Manual may lead to unnecessary replacement of the air condition 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 6000 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-31-4 OF THE 1986 6000 SERVICE MANUAL TO AGREE WITH REVISED ATTACHED SCHEMATIC.