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JCB JZ235, JZ255 Fault Finding Air Conditioning and ATC System Error Codes

JCB JZ235, JZ255  Air Conditioning Fault Finding

Preliminary Checks

Before any checks are carried out on the refrigerant circuit the following checks should be made:

1 Check the compressor drive belt is serviceable and correctly tensioned.
2 Check the condenser and engine radiator are not blocked by debris, clean with compressed air or water if necessary.
3 Check that the condenser fins are not flattened or damaged, the fins must allow air to pass freely.
4 Check the cab fresh air inlet filter for blockage.
5 Check that, with the ignition switch on (engine not running), the blower operates over whole speed range.
6 Check that, with the ignition switch on (engine not running), the blower and air conditioning switched on, the compressor clutch engages.

Charge level:

Note: It is not possible to check refrigerant charge level with R134a systems using the receiver drier sightglass. Any bubbles seen at the sight glass on the receiver drier may be bubbles of oil and are perfectly normal.

– Gas -1400g R134A +/- 10g
– Oil – 150g +/- 5g PAG (PolyAlkylene Gycol) oil to ISO 100

Fault finding:
Important: Refer to appropriate remove and replace procedures before working on any system component

Error Codes / Error Diagnosis (Automatic Temperature Control (ATC) System)

 Table 1. Error Code 1 – High Pressure Lock Out

Effect Description Causes Remedy
The unit cannot cool the cab The compressor disengages. The high pressure switch operates twice In 1 minute. The system is overcharged. Check the continuity of switch (usually open switch).
Check the gas in system and recharge, refer to table.
There is no power to the high pressure switch. Check for 24V at the switch.
Check the continuity between ATC control module pin 33 and switch.
There is a bad earth on the high pressure switch. Check the earth wire between ATC control module pin 34 and switch.
There is a defective switch. Replace the switch.

Table 2. Error Code 2 – Low Pressure Lock Out

Effect Description Causes Remedy
The unit cannot cool the cab The compressor disengages. The high pressure switch operates twice In 1 minute. The system is overcharged. Check the continuity of switch (usually open switch).
Check the gas in system and recharge, refer to table.
There is no power to the high pressure switch. Check for 24V at the switch.
Check the continuity between ATC control module pin 33 and switch.
There is a bad earth on the high pressure switch. Check the earth wire between ATC control module pin 34 and switch.
There is a defective switch. Replace the switch.

Table 3. Error Code 3 – Blower Potentiometer Error (User Interface / Control Panel)

Effect Description Causes Remedy
The Blower motor speed is irregular in Auto mode.The Blower motor speed is fixed or cannot be changed in manual mode.   Wiring Error (open or short-circuit). Check for 24V at blower moto
Check the continuity from blower motor earth to Pin 7 on PWM.
  Check the continuity from pin C15 on user interface to pin 28 on ATC control module. (Expected reading on Pin 28 0.5V to 3.0 V).
Check the continuity between ATC control module pin 33 and switch.
There is no signal from the ATC control module to the PWM. Check the continuity from Pin 5 on ATC control module to Pin 6 on PWM unit.
Bad earth on blower motor / PWM,Defective potentiometer. Check for good earth as shown on schematic.Replace user interface / control panel.

 

 

JCB JZ235, JZ255 REPAIR SERVICE MANUAL

 

 

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