Status Code 33 - Limit Circuit Fault - Bryant 355MAV Troubleshooting Manual

Status Code 33
LIMIT CIRCUIT FAULT - This status code indicates the limit, or flame rollout switch is open or the furnace is operating in high-
heat only mode due to 2 successive low heat limit trips. Blower will run for 4 minutes or until the open switch remakes
whichever is longer. If open longer than 3 minutes, code changes to lockout #13. If open less than 3 minutes status code #33
continues to flash until blower shuts off. Flame rollout switch requires manual reset.
STEP
1. Turn power off, remove blower access panel, and disconnect User Interface ABCD connector
(if used) or the R thermostat lead (if used) from the furnace control board. Note current setting
of setup switch SW1-2 and then set it to the ON position.
2. Turn power on and depress door switch. Use a piece of tape to hold switch closed.
3. Does status code 33 flash?
4. Does a different status code flash?
5. Return setup switch SW1-2 to its original setting and go to page number indicated in the Index
for the section covering the status code.
6. Jumper R and W/W1 thermostat terminals.
7. Observe the furnace operation for 25 minutes or until status code starts flashing.
8. Does status code 33 flash?
9. Does a different status code flash?
10. Return setup switch SW1-2 to its original setting and go to page number indicated in Index for
CLEANUP AND START-UP INSTRUCTIONS.
11. Is 24-vac across connector terminal PL1-6 and C
12. Replace the variable speed furnace control.
13. Is 24-vac across connector terminal PL1-8 and C
14. Turn power off.
15. Do you have continuity across limit switch LS?
16. Wait for unit to cool then recheck for continuity across limit switch LS.
17. Do you have continuity across limit switch LS?
18. Replace limit switch.
19. Do you have continuity across the flame rollout switch FRS?
20. Can flame rollout switch FRS be reset?
21. Replace flame rollout switch FRS.
22. Reset flame rollout switch FRS, turn power on, and observe furnace operation for (2) 15
minute cycles.
23. Does flame rollout switch FRS trip again?
24. Does a different status code flash?
25. You have inadequate combustion-air supply. This may be caused by:
- Reversed vent and combustion-air pipes.
- Poor burner, manifold, or orifice alignment.
- Blocked heat exchanger.
- Leak in secondary heat exchanger.
- Leak somewhere between primary and secondary heat exchangers.
26. Fix problem.
27. While the unit is operating in low heat jumper R and W2.
28. Observe furnace operation for another 10 minutes or until status code 33 starts flashing.
29. Does status code 33 flash?
30. Does a different status code flash?
31. Is the furnace in the downflow or horizontal position?
32. Disconnect the R thermostat lead, wait for blower to stop, and continue to observe furnace for
5 minutes.
33. Does fault occur after blower stops?
34. Increase the blower off-delay time to 180 seconds by putting both setup switches SW1-7 and
SW1-8 into the ON position.
35. Turn power on.
36. Does status code 33 flash?
37. Does a different status code flash?
38. You have an open RED wire or bad terminal in limit circuit. Repair wire or replace harness.
39. Does furnace have the proper limit switch, limit shield, blower baffle (if used), and rear air
baffle (if used)? If so, are the limit switch, limit shield, and heat exchangers properly aligned?
ACTION
-24V on variable speed furnace control?
OM
-24V on variable speed furnace control?
OM
- 23 -
YES NO GO TO
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5 6
INDEX
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40 9
5 27
INDEX
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10
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25 24
5 10
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5 6
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40 26