92-26177-555-01
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14. Install the replacement control in the same position as the original main control (IFC) and snap into
place. Be sure to duplicate the dipswitch selections of the existing controls.
Some functions
previously controlled with dipswitches (blower-off timing (P-6) and single-stage staging selection (P-7)
are controlled with jumper/pins on the replacement control. These jumpers are clearly labeled. Also,
read the notes about thermostat wiring in step 16 for some tips to avoid some potential issues.
15. Connect the wire assembly (modified above with the 12 pin Mate-N-Lok style connector) to plug P-1 on
the replacement control.
16. Reattach the secondary and common leads of the transformer and the inducer control wires to the
replacement control.
17. Reattach the thermostat control wires noting the correct sequence as indicated in step 4 above.
SOME PRECAUTIONS ABOUT THERMOSTAT WIRING FOR SYSTEMS USING A SINGLE-STAGE
THERMOSTAT AND TIMED-STAGING FEATURE:
If furnace control being replaced is connected to a single-stage thermostat and uses the timed
staging feature of the furnace to operate two-stage heat, the following steps and changes must
be made to ensure the same operation.
Instead of routing the heat call “W” from the thermostat to “W2” on the furnace control, the
replacement control requires that the heat call “W” from the thermostat be routed to “W1” on the
furnace control and that the jumper located at “P7” on the furnace control be moved to either
the five-minute (5) or twelve-minute (12) position (depending on the customer’s preference). If
the heat call “W” from the thermostat is routed to “W2” on the furnace control (as before), the
furnace will not
operate in heat.
18. Reattach neutral and line voltage (black and white) leads to the replacement control at the proper
locations (see wiring diagrams).
NOTE: BE SURE TO REATTACH ANY ACCESSORIES (HUMIDIFIER, ELECTRONIC AIR CLEANER,
ETC) THAT MAY BE PRESENT.
19. Install new wire diagram label (90-24314-04) over existing wire diagram label on door.
20. Do not replace the grounding screw through the control board. The replacement control does not need
this screw because the ground wire was installed. There is no clearance hole for it in the replacement
control (refer to steps 8 through 12)
21. Replace furnace access doors.
22. Open the gas stop valve.
23. Restore power to the furnace and actuate heat (test both stages of heat if available) and cooling calls
(test all available) using the thermostat to insure proper operation of the furnace and system.
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