Functional problems (page 2 of 3)

When the external temperature is above 10 ° C start the engine and run it at 1000 r.p.m.. Press the AUTO button engaging the heating-ventilation system and pushing the AIR and TEMP buttons operate the electric fan at the fastest speed and set the lowest temperature possible on the display (LO). After activating the air conditioning system as described above two conditions may occur:

1. the electromagnetic coupling of the compressor pulley is not engaged;
2. the electromagnetic coupling of the compressor pulley engages and disengages cyclically.

In the first case connect the power supply cable of the coupling using a test cable with a fuse to the positive terminal on the battery. If the coupling does not engage after its earth connection has been checked substitute the solenoid. If the coupling engages, disconnect the test cable and measure the pressure in the accumulator-dehydrator (pressure gauge reading on the low pressure side). If the pressure exceeds 3.45 bars short-circuit the pressure switch (located on the hose connecting the evaporator to the accumulator) and check to see if the coupling engages. If it does, replace the pressure switch otherwise check the power supply circuit to see if it is interrupted. If the pressure (low pressure side) is below 3.45 bars, read the pressure value from the pressure gauge on the high pressure side. If the pressure is below 3.45 bars the system is leaking. Find the leak using a leak finder and after having blocked it, dehydrate and refill the system. If the pressure exceeds 3.45 bars, discharge the system and check to see if the high pressure circuit (compressor-evaporator) or the expansion valve are partially blocked. In the second case feel the temperature of the first stretch of hose connecting the the condenser to the evaporator (the high pressure part of the circuit before the expansion valve). If the hose is cold it is partially blocked or squashed and it is necessary to discharge the system, replace the hose and dehydrate and refill the system. If the hose is uniformly warm measure the temperature of the inlet and outlet ducts on the evaporator. If these are at the same temperature or the outlet duct is colder than the inlet, check that the pressure (low pressure side) engages and disengages the electromagnetic coupling of the compressor pulley. The calibration pressures of the pressure switch which serves as a switch for the power supply circuit of the electromagnetic coupling are: circuit closes: 2.826 ÷ 3.516 bars (compressor working); circuit opens: 1.38 ÷ 1.93 bars (compressor off). Three different conditions may arise:

1. the compressor functions continuously and the pressure (low pressure side) is maintained within the limits given above;
2. the compressor functions cyclically within the limits of the pressure limits given above;
3. the compressor cuts in at a pressure above 3.516 bars or cuts out at a pressure below 1.38 bars.