Carrier 58MVP User Manual download pdf (Page 26)

Fault Code 34

IGNITION PROVING FAULT—This fault can indicate 1 of the following:

• Flame was not sensed during trial for ignition period. The control will repeat ignition sequence 3 more times before going into Fault

14—IGNITION LOCKOUT.

• The flame signal was lost after trial for ignition period.

• The flame signal was sensed while gas valve was de-energized. The inducer will run at full speed until fault is cleared.

STEP ACTION YES NO GO TO

Turn power off, remove blower access panel, and disconnect R thermostat lead from furnace con-

trol board.

—— 2

2. Turn power on and depress door switch. Use a piece of tape to hold switch closed. — — 3

Make sure thermostat is NOT calling for heat and reconnect R thermostat lead to furnace control

board. Observe unit for 15 minutes. Does inducer motor ever turn on at full speed while furnace

control board flashes Fault Code 34?

45 —

4. Replace furnace control board. Make sure it has a date code 9405 or later. — — 12

Disconnect R thermostat lead from furnace control board and jumper R and W/W1 thermostat termi-

nals on furnace control board.

—— 6

6. Observe operation of furnace through 1 heating cycle. — — 7

7. Does fault occur again? 13 8 —

8. Does a different fault occur? 910 —

9. Go to page number indicated in Index for fault code flashed. — — INDEX

10. Disconnect jumper wire across R and W/W1 thermostat terminals. Does fault occur now? 11 12 —

11. Replace gas valve. —— 12

12. Go to page number indicated in Index for CLEANUP AND START-UP INSTRUCTIONS. — — INDEX

13. Turn power off and disconnect jumper wire across R and W/W1 thermostat terminals. — — 14

14. Turn power on and wait several sec before proceeding to next step. — — 15

15.

Check hot surface ignitor. To do this, put setup switch SW-6 for COMPONENT TEST in ON posi-

tion. Does ignitor glow orange/white hot by end of 15-sec warm-up period?

20 16 —

16.

Disconnect PL4 from furnace control board. Connect an AC voltmeter across PL4-1 and PL4-2 on

furnace control board. Repeat COMPONENT TEST by turning setup switch SW-6 OFF and then

back ON. Do you see 120 vac across PL4-1 and PL4-2 during 15-sec warm-up period?

18 17 —

17. Replace furnace control board. —— 12

18. Check continuity in harness and ignitor. Replace defective component. — — 19

19. Fix problem. —— 8

20. Put setup switch SW-6 for COMPONENT TEST in OFF position. — — 21

21. Jumper R and W/W1 thermostat terminals on furnace control board. — — 22

22.

Connect an AC voltmeter across BLUE and GREEN wires to gas valve GV. Does gas valve GV re-

ceive 24v?

26 23 —

23. Turn power off. —— 24

24.

Do you have continuity across the following connections:

• PL1-2 and BLUE wire at gas valve GV.

• PL1-7 and GREEN wire at gas valve GV.

17 25 —

25.

The BLUE or GREEN wire from furnace control board to gas valve GV is not making good connec-

tion. Repair wire(s) or replace harness.

—— 12

26. Does gas valve open and allow gas to flow? 28 27 —

27. Are all manual gas cocks in ON position? 11 19 —

28. Do main burners ignite? 30 29 —

29.

Check for the following:

• Inadequate flame carryover or rough ignition.

• Low inlet gas pressure.

—— 19

30. Do main burners stay on? 40 31 —

31. Turn power off and disconnect jumper wire across R and W/W1 thermostat terminals. — — 32

32. Connect a DC microammeter in series with flame sensor wire. — — 33

33.

Turn power on and wait several sec then jumper R and W/W1 thermostat terminals on furnace con-

trol board.

—— 34

34. Is DC current below 0.5 microamps? 36 35 —

35.

Check connections and recheck current. If current is near typical value and control will not stay on,

replace furnace control board.

—— 12

36.

Clean flame sensor with fine sandpaper and recheck current. Current is typically 4.0 to 6.0 micro-

amps.

—— 37

37. Is current near typical value? 39 38 —

38. Replace electrode. —— 12

39. Will main burners ignite and stay on? 12 17 —

40. Do you have combustion pulsations? 41 47 —

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Carrier 58MVP User Manual Page 26

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