IMPROVED A/C PERFORMANCE (REWIRE PUSHER FAN)

VEHICLES AFFECTED: 1989 A-CAR W/3.3L WITH HEAVY DUTY COOLING OPTION

Some owners of 1989 A cars with 3.3L (LG7) engines and heavy duty cooling option (VO8) may comment about the A/C performance on hot days in city driving conditions. This situation occurs because the V08 pusher fan may not come on soon enough to keep the A/C system head pressure below its cutoff value of 400 PSI.

The ECM controls the pusher fan by grounding the pusher fan relay only when the engine coolant temperature reaches 108 degrees C (226 degrees F). The pusher fan is not controlled by a high pressure switch in the A/C system as stated in the Service Manual.

Normal engine cooling (puller fan) is adequate to keep the engine coolant under 108 degrees C (226 degrees F) but does not supply enough cooling to the A/C condenser to keep the A/C head pressure below 400 PSI. This results in an A/C system that cycles around its cutoff pressure of 400 PSI.

Procedure:

Rewire the pusher fan relay so the pusher fan comes on at the same coolant temperature as the puller fan, which is 95 degrees C (202 degrees F). See Figure 1.

1) Loosen fender brace above cooling fan relay bracket and move brace to gain acess to the relays. (See Figure 2).

2) Remove relay bracket and flip relays upside down to access the wiring.

IMPORTANT: The proper way to splice wire is shown in Section 8A of the Service Manual. Use splice clips, solder, and electrical tape or heat shrink tubing to create a splice that will withstand the environment.

3) Cut LT GRN/BLK (536) wire coming from the pusher fan relay.

4) Splice a new black ground wire with a ring terminal on the LT GRN/BLK wire coming from the pusher fan relay end of wire.

5) Attach the ring terminal to ground screw located on the radiator support next to the relay bracket.

6) Tape the other end of the LT GRN/BLK wire leading to the ECM.

7) Cut BRN/WHT (250) wire coming from the pusher fan relay.

8) Splice in a .8mm(18 ga.) BLK/PNK wire to the wire coming out of the relay.

9) Splice the other end of this new BLK/PNK wire onto the BLK/PNK (533) wire at the puller coolant fan relay. (The pusher fan relay also has a BLK/PNK wire, do not splice there.) The BLK/PNK (533) wire at the cooling fan relay should not be cut, the new wire should be spliced onto it.

10) Tape the other end of the BRN/WHT wire leading to the ECM.

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.