Twin Compressor Troubleshooting Guide CKMTA12 CKMTA24

The following describes an effective procedure for tracing an electrical fault in a CKMTA12 or CKMTA24 compressor which has been wired using a genuine ARB wiring loom. All steps must be performed in the order listed here for an accurate assessment.

NOTE: Before attempting to troubleshoot a malfunctioning compressor, always make sure that the compressor manifold, air tanks, and connected accessories have been de-pressurized, all connections have been made according to the wiring diagram, the vehicle's ignition is in the ACC power position, and that the ISOLATING SWITCH has been turned 'ON.'

NOTE: The 'MOTOR VOLTAGE' referred to below should be approximately 12v in the case of the CKMTA12, and 24v in the case of the CKMTA24. Otherwise, 12v refers to approximately 12v regardless of the compressor model as the 24v compressor runs on a 12v control circuit.

1.  Using a multimeter, check voltage at the battery terminals to make sure the battery is working and fully charged. Check each individual 12v battery in a 24v system. 
   
   Did each battery measure at least 11.5 volts?
   
   YES - Proceed to step 2.
   NO - Insufficient battery voltage. Recharge or replace the battery.
   
   
2. Disconnect the compressor motors from the wiring loom at the connector plugs. Run a new wire directly from the negative (-) terminal of the battery to the BLACK wire of the first compressor motor. Momentarily connect a wire from the positive terminal of the battery to the RED wire of the same compressor motor. Repeat this process for the second motor.
   
   Did the compressor activate when the wires were connected?
   
   YES - Remove the extra wires and reconnect the compressor motors. Proceed to step 3.
   NO - Internal compressor motor problem. Contact ARB for further assistance.
   
   
3.  Remove the fuses from the fuse socket in the compressor wiring loom. Using a multimeter, check the resistance (Ohms) across the two contacts of the fuses.
   
   Did the resistance measure less than 1 Ohm?
   
   YES - Proceed to step 4.
   NO - Blown fuse. Replace with a new 40A maxi fuse of the same type. Insert the new fuse with caution in the case a wiring short was responsible for the blown fuse.
   
   
4. Using a multimeter, check for MOTOR VOLTAGE between a chassis ground and each of the two contacts in the fuse sockets.
   
   Was motor voltage detected at one of the two contacts?
   
   YES - Reconnect the fuse into the socket. Proceed to step 5.
   NO - Wiring fault between the positive (+) battery terminal and the fuse socket. Check the wire connection at the battery terminal and/or replace the wiring and/or fuse socket.
   
   
   
5.  Remove the compressor cover as shown below: 
   
   
   Using a multimeter, check for MOTOR VOLTAGE between a chassis ground and the RED wire at each of the relay blocks (ie, the wire leading directly from the fuse).
   
   Was MOTOR VOLTAGE detected?
   
   YES - Proceed to step 6.
   NO - Wiring fault between the fuse and the relay. Replace wiring and/or fuse socket.
   
   
6.  Using a multimeter, check for 12v between the negative (-) terminal of the battery and the RED-YEL wire connected to terminal #2 of the compressor isolating switch. (ie, the wire leading from the vehicle's ACC power).
   
   Was 12v detected?
   
   YES - Proceed to step 7.
   NO - Wire has not been connected correctly or accessory power has not been turned on.                           Attach RED-YEL wire to live ACC power.
   
   
7. Using a multimeter, check for 12v between the negative (-) terminal of the battery and the RED wire connected to terminal #3 of the isolation switch. Test while spade terminals are still connected.
   
   Was approximately 12v detected?
   
   YES - Proceed to step 8.
   NO - Switch fault or switch not turned 'ON' Replace switch or toggle switch to the 'ON' position.
   
   
8.  Using a multimeter, check for 12v between the negative(-) terminal of the battery and the PUR wire connected to the pressure switch attached to the compressor manifold.
   
   Was approximately 12v detected?
   
   YES - Proceed to step 9.
   NO - Wiring fault between isolation switch and the pressure switch. Repair/replace wiring.
   
   
   
9. Using a multimeter, check for 12v between the negative(-) terminal of the battery and the YEL wire connected to the pressure switch attached to the compressor manifold. Test while spade connectors are still connected.
   
   Was approximately 12v detected?
   
   YES - Proceed to step 10.
   NO - Pressure switch fault or tank not de-pressurized. Replace pressure switch or drain tank.
   
   
10. Using a multimeter, check for 12v between the negative(-) terminal of the battery and the YEL wire at each of the relay blocks. (ie, the wire leading directly from the pressure switch)
    
    Was approximately 12v detected?
    
    YES - Proceed to step 11
    NO - Wiring fault between the pressure switch and relay block. Repair/replace wiring.
    
    
    
11. Disconnect the relay from the relay block. Using a multimeter, check the continuity between the BLK wire at the relay block and the negative(-) terminal of the battery.
    
    Did the resistance measure less than 1 Ohm?
    
    YES - Reconnect the relay to the relay block. Proceed to step 12.
    NO - Wiring fault in the ground wire between the battery and the relay block. Repair/replace wiring.
    
    
    
12. Using a multimeter, check for MOTOR VOLTAGE between the negative(-) terminal of the battery and the RED-WHT wire connected to each of the relay blocks and while the relay is still connected. Pierce the RED-WHT wire with the multimeter probes to make connection if necessary.
    
    Was MOTOR VOLTAGE detected?
    
    YES - Proceed to step 13.
    NO - Relay fault. Replace with new 12v - 40amp relay of the same type. ARB# 180905SP
    
    
13. Disconnect the compressor motors from the wiring loom at the connector plug. Using a multimeter, check for MOTOR VOLTAGE between the negative(-) terminal of the battery and the RED-WHT wire on the loom side of the plug.
    
    Was MOTOR VOLTAGE detected?
    
    YES - Proceed to step 14.
    NO - Wiring fault between the relay and the compressor motor connector. Repair/Replace wiring.
    
    
14. Using a multimeter, check the resistance (Ohms) between each of the BLK-WHT wire on the loom side of the plug (not on the compressor side) and the negative(-) terminal of the battery.
    
    Did the resistance measure less than 1 Ohm?
    
    YES - Intermittent wiring fault or internal compressor problem. Contact ARB for further assistance.
    NO - Wiring fault in the ground wire between the battery and the compressor motor. Repair/Replace wiring.