A/C - Insufficient Cooling in High Temperatures
90chevy23GMC NUMBER: 90-1B-85
GROUP: 1B Air Conditioning
DATE: August, 1990
CORPORATE
NUMBER: 061202
SUBJECT: INSUFFICIENT COOLING IN HIGH AMBIENT TEMPERATURES
MODELS: 1988-90 R/V WITH AIR CONDITIONING (RPOs C60 OR C69)
Some of the R/V models from 1988 through 1990, either with or without rear A/C, may receive comments of insufficient cooling in high ambient temperatures. To address this condition a water shut off valve which operates during Max A/C and an insulator cover for the accumulator may be added. In addition, the refrigerant charge has been revised to increase air conditioning performance.
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.
FIGURE 1:
FIGURE 2. VACUUM LINE INSTALLATION:
1. Drain the coolant
2. Cut the front heater inlet and outlet hoses approximately eight inches from the cowl (see Figure 1). It may be necessary to cut about one inch out of each hose to allow the water heater valve
(3) to be inserted. The exact amount of hose will depend on hose routing for different engine configurations and whether the vehicle has a rear heater water valve.
3. Insert the front heater water valve (3) in the hoses and install the hose clamps (1). Torque the clamps to 1.4 - 2.0 N-m (12 - 18 lbs in).
Important
If the wiring for the blower relay evidences any interference with the valve, add convoluted conduit to protect the wires and tie strap the wires as necessary to avoid rubbing.
4. Install the plastic vacuum line on the water valve fitting and add a 3/32 rubber sleeve for coupling (see Figure 1). Route vacuum line with the blower harness to the grommet into the dash area (see Figure 2).
5. Punch a hole in the grommet with a pick, being careful not to puncture existing vacuum lines or wiring harnesses.
FIGURE 4:
FIGURE 3:
6. Route the vacuum line under the dash to the glove box area (see Figure 3).
7. Open the glove box and fold the compartment down to gain access to the rear of the dash. Locate the Max A/C line going to the plenum valve and air recirculation door valve. The line is black plastic with an orange stripe.
8. Cut the line and insert Tee coupling. See view "A" in Figure 3. Use 3/32 rubber vacuum line for the coupling. Install the added vacuum line to the bottom leg of the Tee.
Accumulator Insulation Installation:
1. Install the upper and lower insulators (2) and
(3) on the A/C accumulator assembly (see Figure 4).
2. Install the clamp (4) on the insulators at the overlapped position and tighten the clamp.
Revised Refrigerant Charge:
Important
When possible, use appropriate refrigerant recovery and recycling methods. Refer to Truck Service Bulletin 90-OA-22 (Corporate Number 931203R) for equipment information.
1. Check the refrigerant (Freon 128) pressures per service manual. If discharge pressures are high, revise the A/C charge as follows:
A Front air conditioning (C60): reduce the charge from 3.25 lbs to 3.0 lbs.
B. Rear air conditioning (C69): Reduce charge from 5.25 lbs to 4.5 lbs.
2 Refer to section 1B of the service manual, page 1B-13, for charging and discharging procedures.
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.
PARTS INFORMATION:
WARRANTY INFORMATION For vehicles repaired under warranty use:
Labor Operation: T7001
Labor Time: .7 hr
NOTE: Labor Operation is coded to base vehicle coverage in the warranty system.