BLOCK-WEAR 4503845 - Caterpillar

Introduction
There have been issues with the seat heaters in the above listed machines. The seat heater system operates on 24 VDC, with two 12 VDC heating elements in series. Seat heaters are thermostatically controlled, with one heating element located in the seat cushion, and one heating element located in the seat back cushion. The circuit has two thermostats, a primary and a secondary, that control the seat heater temperature working range. The circuit is designed to operate from the primary thermostat alone. The secondary thermostat is designed as a backup. The design of the seat heater only allows the seat heater to be turned ON if the primary thermostat temperature is below 10 ° 3 °C (50 ° 5 °F), and will shut OFF once the primary thermostat temperature reaches 14 ° 3 °C (57 ° 5 °F) in order to prevent overheating. If the primary thermostat does not open to shut OFF the circuit at 14 ° 3 °C (57 ° 5 °F), the secondary thermostat is designed to turn on at 20 ° 3 °C (68 ° 5 °F) and shut OFF the circuit at 25 ° 3 °C (77 ° 5 °F).
Illustration 1 g01308493
Primary and secondary thermostat locationTest Procedure
In order to test the seat heater, reduce the ambient temperature at the primary thermostat. The temperature should be below the minimum temperature that is required to turn ON the primary thermostat. An ice pack or freeze spray may be used to reduce the temperature. Caterpillar suggests testing the freeze spray in a small area of the seat. The test ensures that no stains will develop.