13
STEP
ACTION YES NO GO TO
10. Disconnect the R thermostat lead. 11
11. Do you have less than 19--vac across R and COM--24V on the variable speed furnace con-
trol?
12 13
12. Replace transformer. 9
13. The thermostat and/or thermostat wires are loading down the transformer. Replace the
thermostat or repair thermostat wires.
9
14. Does the hot surface ignitor HSI come on during the cycle? 15 19
15. Disconnect the humidifier lead from HUM terminal on variable speed furnace control. 16
16. Does the furnace still alternately cycle induced draft motor IDM and blower motor BLWM
asdescribedinStep4.
18 17
17. There is a direct short in wiring to humidifier solenoid coil, diode bridge(if used), or hu-
midifier solenoid coil.
8
18. There is a short in the gas valve GV or wiring to gas valve GV. Refer to Appendix E to
check gas valve GV.
8
19. There is a direct short in the ORANGE wire from the low heat pressure switch LPS. 8
20. While the unit is operating in low heat jumper R and W2 thermostat terminals. 21
21. Does the furnace abruptly shut down with no inducer post purge and then run blower mo-
tor BLWM for 90 seconds while AMBER LED status light flashes status code 12.
22 26
22. Disconnect BROWN wire to gas valve GV. 23
23. Does the furnace still abruptly shut down as described in Step 21. 25 24
24. Replace gas valve. 9
25. There is a direct short to ground in the GRAY or BROWN wires connected to the high heat
pressure switch HPS.
8
26. Power to the furnace was probably interrupted or line voltage was too low during a call for
heat. This is normal operation. Go to the page number indicated in Index for the
CLEANUP AND STARTUP INSTRUCTIONS.
INDEX
Status Code 13
LIMIT CIRCUIT LOCKOUT – Lockout occurs if the limit or flame rollout switch is open longer than 3 minutes or 10 suc-
cessive limit trips occurred during high--heat. The variable speed furnace control will auto--reset in 3 hours. Flame
roll--out switch FRS requires manual--reset.
STEP
ACTION YES NO GO TO
1. Remove the blower access panel. Disconnect the R thermostat lead from the furnace con-
trol board.
2
2. Depress the door switch. Use piece of tape to hold it closed. 3
3. Does status code 33 flash? 11 4
4. Does a different status code flash? 5 6
5. Go to page number indicated in the Index for the section covering the status code. INDEX
6. Jumper R and W/W1 thermostat terminals. 7
7. Observe the furnace operation for 25 minutes or until status code starts flashing. 8
8. Does status code 33 flash? 26 9
9. Does a different status code flash? 5 10
10. Go to page number indicated in Index for CLEANUP AND START--UP INSTRUC-
TIONS.
INDEX
11. Is 24--vac across connector terminal PL1--6 and COM--24V on variable speed furnace con-
trol?
13 12
12. Replace the variable speed furnace control. 10
13. Is 24--vac across connector terminal PL1--8 and COM--24V on variable speed furnace con-
trol?
12 14
14. Turn power off. 15
15. Do you have continuity across limit switch LS? 17 16
16. Replace limit switch LS. 10
17. Do you have continuity across the flame rollout switch FRS? 25 18
18. Can flame rollout switch FRS be reset? 20 19
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