The clearance violation high limit switch (if installed) is located at the front or the back of the painted top panel and extends across the length of the heater. This limit switch monitors the temperature at the top-front of the heater and is connected in series with the Core Charging High Limit Switch to the Limit 1 and Limit 2 terminals on the Base IO Board. To locate the limits, trace the wires from the Base I/O Limit 1 and Limit 2 terminals as placement of the limits has moved over time and wire colors may vary.
The clearance violation limit is a linear high limit which opens on temperature rise. If normal operating temperatures are exceeded, the limit will open and interrupt power to the heating element relays. The heater's control panel will display "CORE FAIL". This limit trips at 183°F/84°C and operating temerpatures at the front panel of the heater are around 150-160°F (65-71°C) when the heater is at full charge. Therefore, anything placed on top of the heater can cause this limit to open.
If the "CORE FAIL" message occurs repeatedly, verify that the heater clearances have not been violated and that objects have not been placed on top of the heater. If clearances are correct, it is possible that the heater is overcharging. Failure of the high limit switch is highly unlikely. If there is continuity (less than 10 ohms) at the leads when the capillary tube is cool and the part is not physically damaged, it can be assumed good.
NOTE: When replacing a high limit switch, DO NOT use water-based lubricant to aid in the installation.
Auto Reset (240°F/116°C), Starting July, 2012 to SN 106132472095579
Manual Reset (183°F/84°C), After SN: 106132472095580
