401333 | Genuine Thermo King® 20A Boost Charger Kit

1. Compatible Thermo King® Units

This boost charger kit is engineered primarily for trailer refrigeration units and multi-temperature systems that experience heavy electrical draws:

• Thermo King Precedent® Series: C-600, S-600, S-700, and multi-temp variations (e.g., C-600M, S-600M).

• Thermo King SB Series: Later production models of the SB-210, SB-230, and SB-330 equipped with compatible electronic interfaces.

2. Application Fitment

• Liftgate Charging Systems: Commonly installed on trailers utilizing electric liftgates to step up voltage and deliver a clean, fast 20-amp charge to the liftgate batteries from the reefer unit's alternator.

• Telematics & Solar Integration: Used in conjunction with Thermo King TracKing® telematics systems and solar panels to manage power distribution effectively.

3. Kit Component Check

When verifying fitment, note that the 401333 kit typically includes:

• The 20A DC-to-DC boost charger module.

• Heavy-gauge marine-grade wiring harnesses with weather-sealed connectors.

• Mounting hardware and inline fuses.

1. What Does It Do?

In standard setups, a tractor's alternator loses voltage by the time the electrical current travels all the way down the long cables to the back of a 53-foot trailer. The Thermo King® Boost Charger solves this by taking the low, dropped voltage and "boosting" it up to a clean, stable 20-amp charge.

2. Primary Functions

• Liftgate Battery Maintenance: It ensures that hydraulic liftgates have enough battery power to operate smoothly at every delivery stop, preventing dead batteries during intense loading/unloading cycles.

• Telematics Protection: It keeps auxiliary batteries charged to power GPS tracking, temperature sensors, and wireless communication systems (like Thermo King TracKing®) even when the main reefer engine is turned off.

• Smart Charging: It uses microprocessors to prevent overcharging and monitors the battery's health, adjusting the voltage based on ambient temperatures.

1. On-Board Diagnostic Fault LED Active

The boost charger module features built-in LED status lights to indicate modes and faults. A specific diagnostic failure LED pattern (or a steady fault light) indicates an internal hardware failure, voltage mismatch, or circuit short.

(Note: A single blinking light usually just means it scaled back power due to high temperatures, which is normal notification, not a total failure).

2. Dead or Constantly Discharged Liftgate/Auxiliary Batteries

The primary job of the charger is to prevent batteries from draining completely during multi-stop delivery routes. If your hydraulic liftgate operates sluggishly, stalls, or the batteries are constantly dead at delivery points, the charger is likely no longer delivering its 20-amp stepped-up voltage.

3. Power Status Light is Completely Off

If the main power status LED on the charger housing is dark while the reefer unit is running or connected to a tractor, it signifies a complete lack of input power or a blown internal/inline fuse. This is often caused by damaged wiring harnesses, loose ground connections in the 7-way nose box, or a fried internal circuit board.

4. Reefer Alarm Code 61 (Low Battery Voltage)

Because the boost charger is integrated into the trailer's electrical ecosystem, a failing unit can place an parasitic load on the starter battery or fail to route power properly. This often triggers Alarm Code 61 on the Thermo King SmartReefer® controller display.

5. Intermittent Telematics Dropouts

If your fleet tracking or TracKing® telematics systems lose connection or shut down shortly after the main reefer engine cycles off, the boost charger has failed to maintain the backup battery storage required to keep these components awake.