How to Test and Adjust Compressor and Relays for Kubota U48 U55 Excavator

This instruction show you guide on how to check test and adjust compressor and relays for Kubota U48-4/U55-4 excavator.

 

Preparations:

2022 Kubota Takeuchi Diagmaster v22.08.01 v4.1.2 Software Free Download
Kubota DST-i Diagnostic Adapter

Kubota EPC Spare Parts Catalogue 2021.06 Download

 

 

Procedures:

Compressor

Magnetic clutch
1 Start the engine.
2 With the AC switch on the AC control panel off, check and make sure that no scraping sounds or other noise comes from the pulley as it turns.
3 Turn the AC switch and the fan switch on to make the AC system operate. With the AC working, check and make sure the magnetic clutch is not slipping.
4 If there is any noise, repair or replace it.

Stator coil
1 Remove the magnetic clutch’s 1P connector.
2 Measure the resistance between the 1P connector on the magnetic clutch side and the body of the stator.
3 If the measurement falls outside of the factory specification,replace the stator coil.

 

 

Relays

After turning the starter switch off, remove the cover under the seat, remove each relay and take the following measurements.

(1) Fuse box (A) Blower motor relay
(B) Compressor clutch relay
(C) Cab relay
(D) Cab work light relay

 

Harness-side checks
Between battery and cab relay
1 Measure the voltage between terminal 1in the fuse box and ground on the body.
2 Set the starter switch to [RUN].
3 Measure the voltage between terminals 3 and 5in the fuse box.
4 If the voltages of each are the same as the battery voltage (DC 11 to 14V), they are normal.

 

Between battery and blower motor relay
1 Measure the voltage between terminal 1in the fuse box and ground on the body.
2 If the voltage is the same as the battery voltage (DC 11 to 14V),it is normal.

Between battery and cab work light relay
1 Measure the voltage between terminal 1in the fuse box and ground on the body.
2 If the voltage is the same as the battery voltage (DC 11 to 14V),it is normal.

Testing individual relays
1 Impress the battery voltage between terminals 3 and 5 of the relay.
2 Check for continuity between terminals 1 and 2 of the relay.
3 If there is continuity between the terminals, it is normal.

(a) Terminal 5
(b) Terminal 3
(c) Terminal 2
(d) Terminal 1
(A) Fuse box terminals
(B) Individual relay

More repair case for Kubota,please refer to:Kubota Trouble Repair