6.7.3 Improper Temperature Control
Temperature control is a function of several interrelated components, each of which must operate correctly. The principle component is the temperature probe. Other components include the inter- face board, the water level sensors (on FBRA18 units), the controller, and the ignition module. Whatever the cause, the symptom is failure of the unit to attain or maintain setpoint temperature.
On FBR18A models, the unit will not call for heat unless the controller senses that the unit is full of water. Sensing is accomplished when the water level in the cookpot contacts the upper water level sensor, grounding it. If the mineral content of the water is unusually low, such as with distilled, pu- rified, or highly filtered water, the water will not ground the sensor. If this is the cause, adding ap- proximately
Similarly, if the upper water level sensor becomes encrusted with lime, starch, or some other build- up, it will not ground properly. The solution is to clean the water level sensors thoroughly with a Scotchbrite™ or similar nylon scouring pad.
6.8Troubleshooting Guides
The troubleshooting guides found in the pages that follow are intended to assist service technicians in quickly isolating the probable causes of equipment malfunctions by following a logical,