Carrier Troubleshooting 58MVP Furnace: Ignition Proving Fault Code 34

Fault Code 34

IGNITION PROVING FAULTÐThis 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

14ÐIGNITION 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
1.	Turn power off, remove blower access panel, and disconnect R thermostat lead from furnace con-		Ð	Ð	2
	trol board.
2.	Turn power on and depress door switch. Use a piece of tape to hold switch closed.		Ð	Ð	3
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		4	5	Ð
	control board flashes Fault Code 34?
4.	Replace furnace control board. Make sure it has a date code 9405 or later.		Ð	Ð	12
5.	Disconnect R thermostat lead from furnace control board and jumper R and W/W1 thermostat termi-		Ð	Ð	6
	nals on furnace control board.
6.	Observe operation of furnace through 1 heating cycle.		Ð	Ð	7
7.	Does fault occur again?		13	8	Ð
8.	Does a different fault occur?		9	10	Ð
9.	Go to page number indicated in Index for fault code flashed.		Ð	Ð	INDEX
10.	Disconnect jumper wire across R and W/W1 thermostat terminals. Does fault occur now?		11	12	Ð
11.	Replace gas valve.		Ð	Ð	12
12.	Go to page number indicated in Index for CLEANUP AND START-UP INSTRUCTIONS.		Ð	Ð	INDEX
13.	Turn power off and disconnect jumper wire across R and W/W1 thermostat terminals.		Ð	Ð	14
14.	Turn power on and wait several sec before proceeding to next step.		Ð	Ð	15
15.	Check hot surface ignitor. To do this, put setup switch SW-6 for COMPONENT TEST in ON posi-		20	16	Ð
	tion. Does ignitor glow orange/white hot by end of 15-sec warm-up period?
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		18	17	Ð
	back ON. Do you see 120 vac across PL4-1 and PL4-2 during 15-sec warm-up period?
17.	Replace furnace control board.		Ð	Ð	12
18.	Check continuity in harness and ignitor. Replace defective component.		Ð	Ð	19
19.	Fix problem.		Ð	Ð	8
20.	Put setup switch SW-6 for COMPONENT TEST in OFF position.		Ð	Ð	21
21.	Jumper R and W/W1 thermostat terminals on furnace control board.		Ð	Ð	22
22.	Connect an AC voltmeter across BLUE and GREEN wires to gas valve GV. Does gas valve GV re-		26	23	Ð
	ceive 24v?
23.	Turn power off.		Ð	Ð	24
24.	Do you have continuity across the following connections:
	· PL1-2 and BLUE wire at gas valve GV.		17	25	Ð
	· PL1-7 and GREEN wire at gas valve GV.
25.	The BLUE or GREEN wire from furnace control board to gas valve GV is not making good connec-		Ð	Ð	12
	tion. Repair wire(s) or replace harness.
26.	Does gas valve open and allow gas to flow?		28	27	Ð
27.	Are all manual gas cocks in ON position?		11	19	Ð
28.	Do main burners ignite?		30	29	Ð
29.	Check for the following:
	·	Inadequate flame carryover or rough ignition.	Ð	Ð	19
	·	Low inlet gas pressure.
30.	Do main burners stay on?		40	31	Ð
31.	Turn power off and disconnect jumper wire across R and W/W1 thermostat terminals.		Ð	Ð	32
32.	Connect a DC microammeter in series with flame sensor wire.		Ð	Ð	33
33.	Turn power on and wait several sec then jumper R and W/W1 thermostat terminals on furnace con-		Ð	Ð	34
	trol board.
34.	Is DC current below 0.5 microamps?		36	35	Ð
35.	Check connections and recheck current. If current is near typical value and control will not stay on,		Ð	Ð	12
	replace furnace control board.
36.	Clean flame sensor with fine sandpaper and recheck current. Current is typically 4.0 to 6.0 micro-		Ð	Ð	37
	amps.
37.	Is current near typical value?		39	38	Ð
38.	Replace electrode.		Ð	Ð	12
39.	Will main burners ignite and stay on?		12	17	Ð
40.	Do you have combustion pulsations?		41	47	Ð

26