1. With the heater off, place the positive (+) lead of a multimeter on the center terminal (1) of the slave
receptacle (2) and the negative lead (-) on the outer metal housing (3). Make note of the voltage
measured. The voltage displayed is the true condition of the batteries charge. The voltage measured
should be very close to 24 VDC.
2. Ensure that all access doors are closed and start the heater. The main control board will delay the
charging until the engine is warmed up; therefore, there will be a delay of approximately 15 seconds.
The main control board in the heater is designed to monitor the engine RPM. If the main
control board senses that the engine is loaded down and is slowing in RPM, the main
control board first disables the charging system for 60 seconds to conserve engine RPM.
After the 60 seconds, the main control board will enable the charging system and perform
an internal test to determine if the engine can handle the load. If the engine can handle
the load, the main control board will leave it enabled. All voltage measurements need to
be viewed with this understanding.
3. After the engine starts, wait approximately 15 seconds and measure the voltage on the batteries
via the slave receptacle (2) as detailed in step 1. If the batteries require charging, the voltage as
measured at the slave receptacle (2) will slowly increase from the voltage that was measured with
the heater OFF and noted in step 1. If the voltage increases as described, the alternator is
operating properly. Alternatively, if the batteries are fully charged, the voltage would jump (after
the 15 seconds) immediately to approximately 28 VDC which would indicate that the alternator is
4. Replace the alternator as detailed in the section of this work package entitled REPLACE if the
alternator is not operating within operational limits as described in the previous two steps.