Ford Workshop Service and Repair Manuals

Inspection and Verification

Visual Inspection Chart

Refrigerant Circuit - Quick Check

WARNING:The air conditioning systems is filled with refrigerant R134a. Observe "Health and Safety Precautions". For further information
REFER to: Health and Safety Precautions (100-00 General Information, Description and Operation).

NOTE:All readings should to be taken at normal ambient temperature with the engine at normal operation temperature.

Refrigerant Circuit Check

WARNING:Under certain circumstances, refrigerant lines and A/C components may be extremely hot or cold. Exercising care, touch the refrigerant lines or A/C components in order to check this. Failure to observe this instruction can lead to injury.

During operation of the air conditioning system, the following conditions shows be apparent:

• The refrigerant line from the A/C compressor to the A/C condenser should be hot.
• The refrigerant line from the refrigerant condenser to the evaporator core orifice of the front A/C system or thermostatic expansion valve of the rear A/C system should be warm, but cooler than the previously mentioned refrigerant line.
• Determine the difference in temperature upstream and downstream of the A/C condenser by measuring the temperatures. The temperature difference should be more than 20°, depending on the ambient temperature. If the temperature difference is less, check the condenser for contamination or damage to the fins as well as operation of the radiator fan.
• The refrigerant line between the evaporator core orifice or thermostatic expansion valve and the evaporator must be cold from the installation position of the evaporator core orifice of the front A/C system or thermostatic expansion valve of the rear A/C system. Depending on the weather, the refrigerant line may also be iced up on the outside.
• The refrigerant line between the evaporator and the A/C compressor should be cold.

Evaporator Outlet Temperature Test

In order to check the A/C output, the temperature of the evaporator outlet line must be measured. The following preparations must be taken for this purpose:

• Open all windows.
• Set the air distribution to the defrost/dashboard position and open all air ducts.
• DO NOT switch on recirculated air.
• Select lowest blower switch setting.
• Select lowest temperature setting.

NOTE:The temperature measurements cannot be performed using a non-contact thermometer. Incorrect measurements result owing to surface reflection.

Connect temperature sensor (Fluke 80 PK-8) to the evaporator outlet line. The temperature sensor must be positioned as closely as possible to the evaporator. Connect the temperature sensor to the digital multimeter.

Start the engine and allow it to run at idle speed for several minutes.

Switch on the air-conditioning system.

After three minutes, measure the surface temperature of the evaporator outlet line.

If the temperature measured is 5° C (vehicles with dual A/C system: 2° C) or lower, the A/C system is OK. If the temperature is higher, the A/C system may be under-filled. For further information
REFER to: Air Conditioning (A/C) System Recovery, Evacuation and Charging (412-00 Climate Control System - General Information, General Procedures).

Frequent faults and their causes

Should a customer express concern about poor cooling performance of the A/C system it must be ensured that actuation of the temperature door(s) is functioning correctly.

• No or poor cooling performance:
  -

  Blockage or restriction in one of the refrigerant lines or in the suction accumulator: By comparing temperatures at the refrigerant lines or at the suction accumulator, the location of the blockage or restriction can easily be identified. The blockage or restriction is located at the point where the temperature difference is identified. Note: A temperature difference in the area of the evaporator core orifice of the front A/C system or thermostatic expansion valve of the rear A/C system is normal. Once the location of the blockage or restriction has been detected, check the relevant component and install new parts if necessary.
• Sudden poor cooling performance. After the compressor has been switched off for approximately 5 minutes, the cooling performance returns to normal:
  -

  The evaporator core orifice of the front A/C system or thermostatic expansion valve of the rear A/C system valve iced-up. The cause for an iced-up evaporator core orifice or thermostatic expansion valve is moisture in the system. In order to ensure that moisture is completely removed from the refrigerant circuit, evacuation time must be extended to 2-3 hours and a new suction accumulator must be installed. For further information REFER to:

  Air Conditioning (A/C) System Recovery, Evacuation and Charging (412-00 Climate Control System - General Information, General Procedures),

  Suction Accumulator (412-03A Air Conditioning, Removal and Installation).

Symptom Chart

Symptom Chart

Pinpoint Tests

Refrigerant Circuit

Workshop Equipment

Servicing unit/pressure gauges

Stopwatch

Electronic leak tester

Leak test

Test all components and refrigerant lines with an electronic leak tester.
REFER to: Electronic Leak Detection (412-00 Climate Control System - General Information, General Procedures).

If necessary switch on the motor and the air conditioning to locate any small leaks in the high-pressure lines.

NOTE:Heavy oil contamination on lines or components is an indication of leaks.

Leaks

In the event of any leaks, rectify the leak(s), renew any faulty components and drain and refill the air conditioning system.

NOTE:The system test is only for vehicles without auxiliary climate control.

System Test

Three values are used for the fault diagnosis:

• Low-pressure
• High-pressure
• A/C compressor switching cycles (on/off)

Connecting the testing equipment

The following requirements must be met in order to carry out an accurate test:

• Close both of the manual valves on the pressure gauges. Connect the pressure gauges to the high-pressure and the low-pressure side of the A/C system.
• Start the engine, set the air conditioning to maximum cooling and air recirculation, and set the blower to maximum power.
• Run the engine at approximately 1500 rpm/min.

Specified values for high and low-pressure

The measured values for high and low-pressure depend on the outside temperature. This is shown in the diagram and the table.

The area between the two curves corresponds to the tolerance range. The measured value must lie in this range.

Specified values for high-pressure

Specified values for low-temperature

Required values: switching cycles

The following three diagrams show the required values for the A/C compressor switching cycles. Measure the cycles using a stopwatch and make a note of the result.

If the measured value lies outside the tolerance range then there is an error in the system. Refer to the Symptom Chart in this section.

NOTE:The total cycle time is obtained by adding the on-time to the off-time.

Specified values for on-time

Specified values for off-time

Specified values for total cycle time

Check the on/off-cycles

The following conditions must be met before checking the switching cycle:

As an example, after comparison with the diagrams the following five faults could be present. Next compare these statements with those in the following symptom chart and read off the cause of the fault.

Example:

• High-pressure - too low
• Low-pressure - normal
• Switching cycles per minute - too many
• Clutch on-time - too short
• Clutch off-time - too short

Fault present: not enough refrigerant in the system.

Symptom Chart - Refrigerant Circuit