Thermo King SB III - Does not stop running in cycle mode

[hueyrescue]

I recently bought a Thermo King SB III with 23k hours for on-site refrigerated storage. I had hoped to set the temp and select the cycle mode so that the system would shut down until it needed to cool down again. However, even in cycle mode, it continues to run as if in continuous mode, using the heater function (and a lot of diesel) to stay in the set temp range. If I switch to continuous and back to cycle, it shuts off (assuming the trailer is at the set temp). But once it kicks back on to start cooling, it does not shut down again. Any help is appreciated.

[DaButcher]

Check battery voltage, amps, and water temp.

All must be within a set range before the unit will cycle off.

What unit do you have SB-III SR, SB-III Max?

[Vandman]

The battery must have a positive charge for the reefer to shut off. if voltage is too low the reefer will continue to run like you said to try and "charge" the battery.

With the reefer running what is your:
Battery voltage
Amps
Water temp?

You will likely need battery and/ or alternator, or possibly Water temp sensor.