302Section 3 A/C controlling systemI. Introduction and CompositionIn order to ensure the effective opeation of the A/C system in any operating condition, some advanced
electric control devices are used to protect the A/C system in adverse engine operating condition.
The electrical control part consists of: A/C switch, relay, evaporator temperature sensor, water temperature
sensor, pressure switch, ECU...etc.
A/C system circuit diagram is shown in Figure 6.II. controlling system feature(1) The condenser fan's power is 90W;
(2) The performance of the condenser fan is controlled by ECU, pressure switch;
(3) Cut off the electrical power of the A/C compressor clutch when the water temperature reaches 109°C;
(4) Connect blower switch 9 to rotate the blower motor 6 to ensure A/C normal operation. Connect A/C
switch 10 to output A/C request signal to ECU.
(5) After ECU receives the request signal and the one from the evaporator temperature sensor 17, if the
engine is at idle, ECU first increases the engine speed to 950 ± 50r/min, lest the A/C operation enhance
the load and lower the engine speed or result in engine off. And then the ECU can respond. If the engine
is in accelerating condition, ECU does not respond immediately either, and respond 5 seconds later after
the end of the accelerating condition. ECU send out a A/C control signal from pin 22 to relay 7, command
the relay to suction in. With the low pressure switch 11 closed, the compressor 12 starts to work when the
magnetic clutch suction on. The condenser relay holds in and condenser blower 13 rotates. When high
pressure switch 15 is closed, have the relay 7 hold in and the water tank fan 14 rotates. When the water
temperature sensor 16's temperature is higher than 109°C, ECU shut off the output signal of the pin 22
and A/C stops operation.
(6) When the Refrigeration system pressure is over 1.7MPa, radiator fan will rotato. Disconnect A/C
compressor Refrigeration system power supply when the pressure is over 2.6MPa or less than 0.25MPa;
305•Compared with the early used mineral oil, the SW-100 type compressor oil is of comparatively high
moisture absorption performance. If you mix the moisture object with the SW-100 type compressor oil, it
will damage the Refrigeration system. Therefore, after treating the compressor oil or removing the
refrigeration system components, the lid shall be covered immediately to prevent the SW-100 type
compressor oil from absorbing the moisture.Section 5 The Refrigeration System Operation ProcedureI. Refill RefrigerantNotice:•During the filling of refrigerant into the refrigeration system, be careful that it is required to
have the professionals operate under the specified standard and procedure, otherwise it will
reduce the A/C efficiency greatly and even damage the refrigeration system components.
Refill the HFC-134a refrigerant
Refill Preparation1. Install the inflating equipment.
2. Connect the low pressure tube to the low pressure
refill valve.
3. Connect the high pressure tube to the high pressure
refill valve.
4. Connect the intermediate tube to the vacuum pump.Vacuumization:1. Open all valves.Notice:•Close all valves of the manifold gauge immediately after the vacuum pump stops operation. If
the valve is still open after the vacuum pump stops operation, then the vacuum pump oil will
return to refrigerant circulation loop and reduce the A/C efficiency.2. Start the vacuum pump and run it for 15min.
3. Check if the readings at high and low sides of the manifold gauge fall within the range of -101 kPa{-760
mmHg }. Close the valves of the manifold gauge.Check the air tightness:1. Stop the vacuum pump and have it wait for 5min.
2. Check the high pressure side of the manifold gauge and the reading at the low pressure side.
•Check for leakage if the reading changes and vacuumize it again.
•Refill the new HRC-134a refrigerant if the reading doesn't change.To low pressure fill valveLow Pressure GaugeHigh Pressure
GaugeConnect the high
pressure refill valveLow Pressure TubeHigh Pressure TubeLow Pressure
Manual ValveHigh Pressure
Manual ValveVacuum PumpIntermediate Tube
Refrigerant Steel Jar
3063. Check for leakage if the reading changes and vacuumize it again.
4. Refill the new HFC-134a refrigerant if the reading doesn’t change.
Fill the new HFC-134a refrigerant
1. Connect the intermediate pipe to the refrigerant steel jar.
2. Open the refrigerant steel jar valve.
3. Weigh the refrigerant steel jar to charge the right refrigerant volume (refrigerant refill 630g¡À20g).Warning:•Check for air leakage or any other leakage when refilling large amount of refrigerant into the
Refrigeration system. The operator is recommended to fill small amount of refrigerant first to
prevent the refrigerant from leakage, which will result in ozonosphere damage.•It is very dangerous to open the engine high pressure side valve if filling the refrigerant with
the service tank. The pressure in the service tank will rise during the operation, which will
result in the service tank explosion. The exploded mental fragment and the splashed refrigerant
will hurt the operator badly. Therefore, do close the high pressure side valve when the engine
is working.4. Open the manifold gauge low pressure side valve.
5. Close the manifold gauge low pressure side valve when the manifold gauge low pressure side reading is
increased to 0.098Mpa{1.0kgf/cm2}.
6. Check cooling pipeline/hose for leakage with leak detector.
•Proceed to step 8 if there is no leakage.
•Tighten the union joint if there is leakage at the loosened union joint and go to next step.
7. Re-check the leaked points.
•Go to next step if there is no leakage after tightening the union joint.
•If there is still leakage at the same union joint, drain refrigerant and repair the union joint. Repeat
the filling procedure and vacuum it.
8. Open the valve at the low pressure side of the manifold gauge. Fill the refrigerant until the refrigerant
tank weight from the one mentioned in Step 3 drop to 250g.
9. Close the valve at the low pressure side of the manifold gauge.
10. Start the engine and switch on A/C.
11. Open the valve at the low pressure side of the manifold gauge. Fill the refrigerant until the refrigerant
tank weight from the one mentioned in Step 3 to specified value.
12. Close the valve at the low pressure side of the manifold gauge and the valve of the refrigerant steel jar.
13. Stop the engine and A/C compressor.
