Heating & Air Conditioning: Other Dodge Pickup R2500

HEATER AND AIR CONDITIONER

All vehicles are equipped with a common HVAC housing assembly (Scheme 1) The system combines air conditioning, heating, and ventilating capabilities in a single unit housing mounted under the instrument panel.

Scheme 1

COOLING SYSTEM REQUIREMENTS

To maintain the performance level of the HVAC system, the engine cooling system must be properly maintained. The use of a bug screen is not recommended. Any obstructions in front of the radiator or condenser will reduce the performance of the air conditioning and engine cooling systems.

The engine cooling system includes the heater core and the heater hoses. Refer to COOLING for more information before the opening of, or attempting any service to the engine cooling system.

REFRIGERANT SYSTEM SERVICE PORT

The two refrigerant system service ports are used to charge, recover/recycle, evacuate, and test the air conditioning refrigerant system. Unique service port coupler sizes are used on the R-134a system, to ensure that the refrigerant system is not accidentally contaminated by the use of the wrong refrigerant (R-12), or refrigerant system service equipment.

The heater air conditioner are blend-air type systems. In a blend-air system, a blend door controls the amount of unconditioned air (or cooled air from the evaporator on models with air conditioning) that is allowed to flow through, or around, the heater core. A temperature control knob on the A/C Heater control panel determines the discharge air temperature by controlling an electric actuator, which moves the blend door. This allows an almost immediate control of the output air temperature of the system.

The mode control knob on the A/C Heater control panel is used to direct the conditioned air to the selected system outlets. Both mode control switches use electric actuators to control the mode doors.

On all vehicles, the outside air intake can be shut off by selecting the Recirculation Mode with the mode control knob. This will operate a electric actuated recirculation door that closes off the outside fresh air intake and recirculates the air that is already inside the vehicle.

The air conditioner for all models is designed for the use of non-CFC, R-134a refrigerant. The air conditioning system has an evaporator to cool and dehumidify the incoming air prior to blending it with the heated air. This air conditioning system uses a fixed orifice tube in the liquid line near the condenser outlet tube to meter refrigerant flow to the evaporator coil. To maintain minimum evaporator temperature and prevent evaporator freezing, the A/C Fin Probe which is located in the evaporator cycles the compressor clutch by sending an A/C request to the JTEC which in turn processes this piece of information and if all conditions are met cycles the compressor clutch.

The low pressure service port is located on the suction refrigerant line, near the accumulator. The high pressure service port is located on the liquid line at the passenger side of the engine compartment, near the condenser.

Each of the service ports has a threaded plastic protective cap installed over it from the factory. After servicing the refrigerant system, always reinstall both of the service port caps.

A/C PERFORMANCE

The air conditioning system is designed to provide the passenger compartment with low temperature and low humidity air. The evaporator, located in the HVAC housing on the dash panel below the instrument panel, is cooled to temperatures near the freezing point. As warm damp air passes through the cooled evaporator, the air transfers its heat to the refrigerant in the evaporator and the moisture in the air condenses on the evaporator fins. During periods of high heat and humidity, an air conditioning system will be more effective in the Recirculation Mode. With the system in the Recirculation Mode, only air from the passenger compartment passes through the evaporator. As the passenger compartment air dehumidifies, the air conditioning system performance levels improve.

Humidity has an important bearing on the temperature of the air delivered to the interior of the vehicle. It is important to understand the effect that humidity has on the performance of the air conditioning system. When humidity is high, the evaporator has to perform a double duty. It must lower the air temperature, and it must lower the temperature of the moisture in the air that condenses on the evaporator fins. Condensing the moisture in the air transfers heat energy into the evaporator fins and tubing. This reduces the amount of heat the evaporator can absorb from the air. High humidity greatly reduces the ability of the evaporator to lower the temperature of the air.

However, evaporator capacity used to reduce the amount of moisture in the air is not wasted. Removing some of the moisture out of the air entering the vehicle adds to the comfort of the passengers. Although, an owner may expect too much from the air conditioning system on humid days. A performance test is the best way to determine whether the system is performing up to standard. This test also provides valuable clues as to the possible cause of trouble with the air conditioning system.

Note. Before proceeding, refer to PLUMBING .

The air temperature in the test room and in the vehicle must be a minimum of 21° C (70° F) for this test.

Scheme 2

Scheme 3

Scheme 4

1. Connect a tachometer and a manifold gauge set or A/C recycling/charging station.
2. Set the A/C Heater mode control switch knob in the Recirculation Mode position, the temperature control knob in the full cool position, and the blower motor switch knob in the highest speed position.
3. Start the engine and hold the idle at 1,000 rpm with the compressor clutch engaged.
4. The engine should be at operating temperature. The doors and windows must be closed.
5. Insert a thermometer in the driver side center A/C (panel) outlet. Operate the engine for five minutes.
6. The compressor clutch may cycle, depending upon the ambient temperature and humidity.
7. With the compressor clutch engaged, record the discharge air temperature and the compressor discharge pressure.
8. Compare the discharge air temperature to the Performance Temperature and Pressure chart. If the discharge air temperature is high, refer to «DIAGNOSIS AND TESTING - REFRIGERANT SYSTEM LEAKS»(ref-189725-S03301115842005091100000) and to «SPECIFICATIONS - CHARGE CAPACITY»(ref-189725-S18731177102005091100000). PAYING ATTENTION TO CURRENT FLOW DIRECTION WHILE REMOVING DIODE FROM HARNESS Performance Temperature and Pressure Ambient Air Temperature 21° C (70° F) 27° C (80° F) 32° C (90° F) 38° C (100° F) 43° C (110° F) Air Temperature at Center Panel Outlet 7° C (45° F) 7° C (45° F) 13° C (55° F) 13° C (55° F) 18° C (64° F) Compressor Inlet Pressure at Service Port (low Side) 138 to 207 kPa (20 to 30 psi) 172 to 241 kPa (25 to 35 psi) 207 to 276 kPa (30 to 40 psi) 241 to 310 kPa (35 to 45 psi) 276 to 345 kPa (40 to 50 psi) Condensor Out Pressuree at Service Port (High Side) 1034 to 1724 kPa (150 to 250 psi) 1379 to 2068 kPa (200 to 300 psi) 1724 to 2413 kPa (250 to 350 psi) 1999 to 2689 kPa (290 to 390 psi) 2413 to 2965 kPa (350 to 430 psi)
9. Compare the compressor discharge pressure to the Performance Temperature and Pressure chart (Scheme 2) If the compressor discharge pressure is high, see the Pressure Diagnosis chart ( (Scheme 3) & (Scheme 4) ).

HEATER PERFORMANCE

Before performing the following tests, refer to COOLING for the procedures to check the engine coolant level and flow, engine coolant reserve/recovery system operation, accessory drive belt condition and tension, radiator air flow and the fan drive operation. Also be certain that the accessory vacuum supply line is connected at the engine vacuum source.

MAXIMUM HEATER OUTPUT

Engine coolant is delivered to the heater core through two heater hoses. With the engine idling at normal operating temperature, set the temperature control knob in the full hot position, the mode control switch knob in the floor position, and the blower motor switch knob in the highest speed position. Using a test thermometer, check the temperature of the air being discharged at the HVAC housing floor outlets. Compare the test thermometer reading to the Temperature Reference chart.

TEMPERATURE REFERENCE CHART

If the floor outlet air temperature is too low, refer to COOLING to check the engine coolant temperature specifications. Both of the heater hoses should be hot to the touch. The coolant return heater hose should be slightly cooler than the coolant supply heater hose. If the return hose is much cooler than the supply hose, locate and repair the engine coolant flow obstruction in the cooling system. Refer to COOLING for the procedures.

An alternate method of checking heater performance is to use a DRBIII(R) scan tool to monitor the engine coolant temperature. The floor outlet air temperature reading should be no more than 4.5° C (40° F) lower than the engine coolant temperature reading.

OBSTRUCTED COOLANT FLOW Possible locations or causes of obstructed coolant flow

1. Faulty water pump.
2. Faulty thermostat.
3. Pinched or kinked heater hoses.
4. Improper heater hose routing.
5. Plugged heater hoses or supply and return ports at the cooling system connections.
6. A plugged heater core.

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

MECHANICAL PROBLEMS Possible locations or causes of insufficient heat

1. An obstructed cowl air intake.
2. Obstructed heater system outlets.
3. A faulty, obstructed or improperly installed blend door.
4. A faulty blower system.
5. A faulty a/c heater control.

TEMPERATURE CONTROL

If the heater outlet air temperature cannot be adjusted with the temperature control knob on the a/c heater control panel, the following could require service: (also (Scheme 5)

1. A faulty a/c heater control.
2. A faulty blend door actuator.
3. A faulty, obstructed or improperly installed blend door.
4. An obstructed cowl air intake.
5. The engine cooling system.

Scheme 5

1. Disconnect the battery negative cable and isolate it. If vehicle has a dual batteries remove both negative cables.
2. Locate the diode in the harness, and remove the protective covering.
3. Remove the diode from the harness, pay attention to the current flow direction see scheme 6
4. Remove the insulation from the wires in the harness. Only remove enough insulation to solder in the new diode.
5. Install the new diode in the harness, making sure current flow is correct. If necessary refer to the appropriate wiring diagram for current flow.
6. Solder the connections together using rosin core type solder only. Do not use acid core solder.
7. Tape the diode to the harness using electrical tape making, sure the diode is completely sealed from the elements.
8. Re-connect the battery negative cable(s), and test affected systems.