Bosch Appliances TRUE, 6806, 6805, 4306, 4302, 6802 manual NTC Operation

52 H

NTC Operation

Fig. 14-1

Located on top of the Heater Assembly is the NTC (Negative Temperature Coefficient), Fig. 14-1. The NTC uses resistance to control wash and rinse water temperature and is connected with two green leads.

As water temperature increases, the NTC records the decrease in resistance. The Control Unit Logic Board measures this resistance change and allows the program to advance once the correct temperature (resistance level) is reached.

Service note: The SHU 30** and SHU 40** models do not use an NTC, but utilize a standard, normally open thermostat (bi-metal).

Also combined within the NTC (or standard thermostat) is a High Limit Safety Thermostat, connected with red leads. The normally closed high limit is set to 185° Fahrenheit and is self-resetting.

Service tip: The NTC can be checked without removing the dishwasher by measuring its resistance at the Control Unit. Using the appropriate wiring diagram, locate the two NTC leads. The resistance at room temperature should be approximately 55k Ohms.

An extremely high, low or no Ohm reading will usually indicate a faulty NTC.