LOSS OF A/C COOLING/FAN INOP FAILED COMP. SWITCH/RELAY INOP

VEHICLES AFFECTED: 1984 Corvette

Some early production vehicles may experience a loss of cooling from the air conditioning system. This may be caused by a short in the compressor pressure switch system, causing the cooling fan relay to become inoperative.

The pressure switch and relay is used to start the electric fan motor when the A/C system pressure reaches a certain level. These vehicles had changes made in the 'pressure switch system'.

The changes consisted of:

1. Adding an auxiliary fan pressure switch, on the A/C pipe pressure tap.

2. Adding a new auxiliary wire harness which runs from the connection near the A/C compressor to the new auxiliary fan pressure switch and a ground wire from the auxiliary fan pressure switch to the frame rail.

In the event that cooling fan conditions are experienced on vehicles with this auxiliary system, the following procedure should be followed:

1. Observe the fan pressure switch on the A/C compressor (refer to Sketch 1). If the wire harness is connected to the pressure switch, the system has not been revised and this bulletin or following steps do not apply. If the wire harness is not connected to the fan pressure switch on the A/C compressor but is instead connected to a auxiliary jumper harness, proceed to Step 2.

2. Check fan relay for proper operation and/or burned contacts, replace if necessary. The relay is located at rear of the left front wheel house cover.

3. Check the auxiliary fan pressure switch. If replacement is necessary, the vehicle will have to be changed back to the original design. The existing disconnected pressure switch in the compressor will have to be changed according to service manual instructions, including discharging the A/C system.

4. Obtain new two-piece plastic connector (P/N 12015375 and P/N 12014836) for the wiring harness connection from the new original production fan pressure switch (P/N 2724279) located on the compressor to the existing in-line terminal connector at tne auxiliary wire harness connection.

5. After replacement of switch and connector, the auxiliary harness and pressure switch can be discarded. After removing and discarding the old pressure switch from the A/C pressure tap, install a cap (P/N 3033974) on the tap fitting.

If similar conditons are experienced on vehicles without the auxiliary system, the same procedure of checking the relay and replacing the compressor fan switch should be observed, except for the new plastic connector for wiring harness.

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.