THIS PROCEDURE MUST BE PERFORMED BY A QUALIFIED TECHNICIAN.
THIS PROCEDURE MUST BE PERFORMED BY A QUALIFIED TECHNICIAN.
The base I/O relay board provides internal power to the logic of all circuit boards in the system. Input power is applied to the L1 and L2 240 terminals on the base I/O relay board. This board has two fuses that operate as follows:
The 1/4-amp fuse (Part #1024036) provides power to all the circuit boards in the system. If this fuse is open, the system's display does not illuminate. This input has over voltage circuit protection; therefore, a high voltage surge or incorrect input voltage wiring are the most common cause for the fuse to open.
The 5-amp fuse (Part #1024037) protects the variable voltage (triac) outputs for the core blower and air handler pump control. These outputs pass voltage from the L1 terminal to the blower and damper output terminals. If this fuse is open, the most probable causes include a shorted blower, wiring to the air handler pump, or a failed pump. The primary loop pump is not fused.
07/14/06 Rev 1