Tripac APU Error Code 25 Alternator Check.

TriPac shuts down to prevent discharged truck batteries. Take off cables from the batteries and clean them with metal brush. Then check all batteries to see if there are any dead ones. Connect software and run Alternator Test. Should be getting charge of 10+amps. Ideally 30+. If the charge is negative during test - replace alternator.

Component Description and Location.

The battery voltage is sensed at the SEN (J14 PinA1) connection on the interface board.

The charge current is sensed by the Current Sensor (CS). This sensor is mounted where the batterty cable enters the APU.

Circuit Description

The sensed battery voltage is low enough to cause the alternator to be charging. The current sensor determines the alternator is not sending current to the truck batteries. TriPac shuts down to prevent discharged truck batteries. 

Diagnostic procedure.

Use an external amp clamp on the positive battery cable to verify actual amperage. 

Refer to Alternator Diagnosis earlier in this section.