Файл: 92FWD_24.pdf

GENERAL INFORMATION

Use an adjustable Vacuum Test Gauge (C-3707) and a suitable vacuum pump to test heater A/C control vacuum. With a finger placed over the end of test hose (Fig. 1), calibrate vacuum control valve on the test gauge to obtain -27 kPa (8 in. Hg.). Release and block the end of the test hose several times to verify vacuum setting.

Fig. 1 Adjust Vacuum Test Bleed Valve

VACUUM TESTING THE ONE-WAY CHECK VALVE

(1)In the engine compartment, disconnect the Heater-A/C vacuum supply (black) hose. This hose passes through an opening in the dash panel used for the air conditioning expansion valve.

(2)Remove the vacuum check valve. This valve is located on the (black) vacuum supply hose at the brake power booster.

(3)Connect test vacuum supply hose to the heater side of the valve. In this direction the gauge should return to calibrated setting. If valve leaks vacuum in this direction, valve replacement is necessary.

(4)Connect test vacuum supply hose to the engine vacuum side of the valve. Vacuum should flow through valve.

VACUUM TESTING THE HEATER-A/C CONTROLS

(1)Connect the test vacuum prod to the vehicles (black) vacuum supply hose. Position vacuum test gauge so it can be viewed from the passenger compartment.

(2)Position the heater A/C control mode selector to DEFROST, FLOOR, BI-LEVEL, PANEL, and RECIRC (with A/C). Pause after each selection. The test gauge should return to the calibrated setting of -27

kPa (8 in. Hg.) after each selection is made. If the gauge cannot achieve the calibrated setting, a vacuum circuit or component has a leak.

LOCATING VACUUM LEAKS

To locate a vacuum leak, disconnect 7-way vacuum connector behind the instrument panel at the heater A/C control. For removal and installation of heater A/C control panel, refer to the Switch and Panel Component Service section of Group 8E, Instrument Panel. Connect the calibrated vacuum hose prod (Fig. 4) to each port in the vacuum harness connector (Fig. 2). The brown, bi-level, vacuum circuit has a metal fiber restrictive device located in the line. More reaction time is required for the test gauge to return to calibrated setting. After each connection is made, the test gauge should return to calibrated setting. If all circuits function properly, replace control mode vacuum switch. If not, determine the color of the vacuum circuit that is leaking. To determine vacuum line colors, refer to the Vacuum Circuits-Heater or Heater A/C Control chart in this section. Disconnect the vacuum actuator at the other end of the circuit. (Instrument panel removal may be necessary to gain access to some components). Block the end of the disconnected vacuum line. The test gauge should return to calibrated setting. If not, that circuit has a leak and must be repaired or replaced. If test gauge returns to calibrated setting, the vacuum actuator must be replaced.

HEATER OUTPUT TEST

PRE-DIAGNOSTIC PREPARATIONS

Review Safety Precautions and Warnings before performing the following procedures.

Check the radiator coolant level, drive belt tension, and engine vacuum line connections. Also check radiator air flow and radiator fan operation. Start engine and allow to warm up to normal operating temperature.

WARNING: DO NOT REMOVE RADIATOR CAP WHEN ENGINE IS HOT, PERSONAL INJURY CAN RESULT.

If vehicle has been run recently, wait 15 minutes before removing cap. Place a rag over the cap and turn it to the first safety stop. Allow pressure to escape through the overflow tube. When the system stabilizes, remove the cap completely.

MAXIMUM HEATER OUTPUT:TEST AND ACTION

Engine coolant is provided to the heater system by two 16 mm (5/8 inch inside diameter) heater hoses. With engine idling at normal running temperature, set the control to maximum heat, floor, and high blower setting. Using a test thermometer, check the air temperature coming from the floor outlets, refer to Temperature Reference chart.

TEMPERATURE REFERENCE CHART

If the floor outlet air temperature is low, refer to Group 7, Cooling System for coolant temperature specifications. Both heater hoses should be HOT to the touch. The coolant return hose should be slightly cooler than the supply hose. If coolant return hose is much cooler than the supply hose, locate and repair engine coolant flow obstruction in heater system.

POSSIBLE LOCATIONS OR CAUSE OF OBSTRUCTED COOLANT FLOW

(a)Pinched or kinked heater hoses.

(b)Improper heater hose routing.

(c)Plugged heater hoses or supply and return ports at cooling system connections, refer to Group 7, Cooling System.

(d)Plugged heater core.

(e)Water valve sticking or inoperative.

If proper coolant flow through heater system is verified and outlet air temperature is still low, a mechanical problem may exist.

POSSIBLE LOCATION OR CAUSE OF INSUFFICIENT HEAT

(a)Obstructed cowl air intake.

(b)Obstructed heater system outlets.

(c)Blend-air door not functioning properly.

TEMPERATURE CONTROL

If temperature cannot be adjusted with the TEMP lever on the control panel, or TEMP lever is difficult to move, the following could require service:

(a)Blend-air door binding.

(b)Control cables miss-routed, pinched, kinked, or disconnected.

(c)Improper engine coolant temperature.

A/C PERFORMANCE TEST

The air-conditioning system is designed to remove heat and humidity from the air entering the passenger compartment. The evaporator, located in the heater A/C unit behind the instrument panel, is cooled to temperatures near the freezing point. As warm damp air passes over the fins in the evaporator, moisture in the air condenses to water, dehumidifying the air. Condensation on the evaporator fins reduces the evaporators ability to absorb heat. During periods of high heat and humidity an A/C system will be less effective than during periods of high heat and low humidity. With the instrument control set to RECIRC, only air from the passenger compartment passes through the evaporator. As the passenger compartment air dehumidifies, A/C performance levels rise.

PERFORMANCE TEST PROCEDURE

Review Safety Precautions and Warnings before proceeding with this procedure. Air temperature in test room and on vehicle must be 70°F (21°C) minimum for this test.

(1)Connect a tachometer and manifold gauge set.

(2)Set control to A/C, RECIRC, PANEL, or MAX A/C, temperature lever on full cool and blower on high.

(3)Start engine and hold at 1000 rpm with A/C clutch engaged.

(4)Engine should be warmed up with doors and windows closed.

SIGHT GLASS REFRIGERANT LEVEL INSPECTION

The filter-drier is equipped with a sight glass (Fig. 1) that is used as a refrigerant level indicator only. This sight glass is not to be used for A/C performance testing. To check the refrigerant level remove the vehicle jack. Then clean the sight glass, start and warm up engine, and hold rpm slightly above idle (1100 rpm). Place the air-conditioning control on A/C, RECIRC and high blower. The work area should be at least 21°C (70°F). If a Fixed Displacement type compressor does not engage, the refrigerant level is probably too low for the Low Pressure Cut-Off switch to detect. Or, with a Variable Displacement compressor, for the Differential Pressure Cut-off to detect. If compressor clutch does not engage, test the refrigerant system for leaks. If compressor clutch engages, allow approximately one minute for refrigerant to stabilize. View refrigerant through sight glass. The suction line should be cold to the touch and the sight glass should be clear.

Fig. 1 Filter Drier and Sight Glass

bubbles are normal when the work area temperature is above 43°C (110°F) or below 21°C (70°F). If suction line is cold and occasional bubbles are visible in the sight glass, block the condenser air flow. This will increase the compressor discharge pressure (Do not allow engine to over heat). Bubbles should dissipate. If not, the refrigerant level is low.

WARNING: R-12 REFRIGERANT IS DETRIMENTAL TO THE ENVIRONMENT WHEN RELEASED TO THE ATMOSPHERE. DO NOT RECHARGE AN A/C SYSTEM BY ADDING R-12 REFRIGERANT TO A SYSTEM THAT HAS A KNOWN LEAK.

The refrigerant system will not be low on (R-12) unless there is a leak. Find and repair the leak before charging.

R-12 REFRIGERANT EQUIPMENT

WARNING: EYE PROTECTION MUST BE USED WHEN SERVICING AN AIR-CONDITIONING REFRIGERANT SYSTEM. TURN OFF (ROTATE CLOCKWISE) ALL VALVES ON THE EQUIPMENT BEING USED BEFORE PROCEEDING WITH THIS OPERATION. PERSONNEL INJURY CAN RESULT.

When servicing an air-conditioning system, an A/C charging station is recommended (Fig. 2). An (R-12) refrigerant recovery/recycling device (Fig. 3) should also be used. This device should meet SAE standard J1991. Contact an automotive service equipment supplier for refrigerant recycling/recovering equipment. Refer to the operating instructions provided with the equipment for proper operation.

A manifold gauge set (Fig. 4) must also be used in conjunction with the charging and/or recovery/recycling device. The service hoses on the gauge set being used should have manual (turn wheel) or automatic back flow valves at the service port connector ends. This will prevent refrigerant from being release into the atmosphere.

REFRIGERANT RECYCLING

If foam or bubbles are visible in sight glass, the refrigerant level is probably low. Occasional foam or

(R-12) refrigerant is a chlorofluorocarbon (CFC) that can contribute to the depletion of the ozone