A/C - Insufficient Cooling in High Ambient Temperatures
File In Section: 1 - HVACBulletin No.: 06-12-03
Date: October, 1994
Subject:
Insufficient Cooling in High Ambient Temperature (Install Water Valve/Insulator Cover and Underbody Shield)
Models:
1988-94 Chevrolet and GMC Truck S/T Models
1991-94 Oldsmobile Bravada with Air Conditioning (RPO C60)
This bulletin is being revised to add the 1993 and 1994 model years. Previous divisional publication numbers were:
Chevrolet 91-42A-1B
GMC Truck 91-1B-165
Oldsmobile 91-T-232
GM of Canada 92-1-117
Some owners may experience insufficient cooling in high ambient temperatures (90~F or higher, with relative humidity of 90% or higher). To address this condition two service modifications have been developed.
1. Installation of coolant shut off valve which actuates in A/C Max mode and an insulated cover for the accumulator.
2. Installation of an under body shield, P/N 15564769, to improve cooling and direct air flow through the condenser (T-Truck only).
Service Procedures
Water Valve Installation:
Caution:
Coolant may be pressurized and hot. Use care to ensure that the coolant Is at ambient temperature. Possible burns could result from contact with hot coolant
1. Drain the coolant.
2. Cut the heater inlet and outlet hoses approximately 88.9 mm (3.5 in.) from the cowl (Figure 1).
It may be necessary to cut about one inch out of each hose to allow the water heater valve (4) to be inserted. The exact amount of hose will depend on hose routing for different engine configurations.
3. Insert the heater water valve, P/N 14044414, (Figure 1, Item 4) in the hoses and install the hose clamps, P/N 12337891, (Figure 1, Item 2). Torque the clamps to 1.4 - 2.0 N-m (12 - 18 lb.in.).
Important:
If the wiring for the blower relay shows evidence of interference with the valve, add convoluted conduit to protect the wires and tie strap the wires as necessary to avoid rubbing.
4. Install plastic vacuum line on the water valve fitting and add a 2.4 mm (3/32 in.) rubber sleeve for coupling (Figure 1). Route vacuum line with the antenna cable to the grommet into the dash area (Figure 2).
5. Punch a hole in the grommet with a pick, being careful not to puncture the antenna cable.
6. Route the vacuum line under the dash to the glove box area (Figure 3).
7. Open the glove box and remove the rear panel to gain access to the rear of the dash. It will also be necessary to remove the insulator assembly under the dash for full access. Locate the Max A/C line going to the plenum valve and the air recirculation door valve. The line is black plastic with an orange stripe.
8. Cut the line and insert Tee coupling, P/N 6272766, (Figure 3, View A). Use 2.4 mm (3/32 in) rubber vacuum line for the couplings. Install the added vacuum line to the bottom leg of the Tee.
9. Reinstall under dash insulator and the rear panel of the glove box door.
Accumulator Insulation Installation:
1. Install the upper and lower insulators, P/N 15612121 and 15612120, (Figure 4, Items 3 and 4) on the A/C accumulator assembly.
Important:
The insulator is designed for a G van and must be modified for use on an S/T truck accumulator.
2. Cut the lower insulator as necessary to fit the accumulator mounting bracket. Cut the upper insulator as necessary to accommodate the A/C pipes and fittings.
3. Install the clamp, P/N 15530486, (Figure 4, Item 2) on the insulators at the overlapped portion and tighten the clamp.
Inspection:
1. Start the engine and check all hose connections for leaks.
2. Place the climate control lever in the "Max A/C" position and ensure that the water valve is operating properly
Underbody Shield Installation (T-Truck w/o ZM5 underbody shield opt.)
Note:
Installation of this shield will improve engine cooling and assist in directing air flow through the condenser and radiator.
1. Raise vehicle on a hoist to access the underbody.
2. Place the shield, P/N 15564769, so that the back edge rests on the front cross member and the front outer edges rest on the frame rails (Figure 5).
3. Align the shield attachment holes with the predrilled threaded holes on the front crossmember and frame rails.
4. Torque the six (6) attachment bolts, P/N 11509171, and washers, P/N 15596486, to 38 N-m (8.5 lb.ft.)
5. Lower the vehicle on the hoist.
Service Parts information
Parts are currently available from GMSPO.
Warranty Information
For vehicles repaired under warranty use:
Note:
Labor Operation is coded to base vehicle coverage in the warranty system.