STEP
ACTION
YES
NO
GO TO
52.
The problem is caused by modulating zone damper system. Check zoning sys-
tem manufacturer’s Installation and Troubleshooting Guide for corrective action.
—
—
10
53.
Turn power off and install a temperature probe in front of limit switch button.
—
—
54
54.
Turn power on and cycle unit. Does limit switch open at a temperature at least
10°F below temperature setpoint for limit switch?
EXAMPLE: The setpoint is 220°F, but switch opens at a temperature below
210°F.
19
55
—
55.
Adjust blower speed to get temperature rise within rise range.
—
—
27
56.
Turn power off and install a temperature probe in front of limit switch button.
—
—
57
57.
Turn power on and cycle unit. Does limit switch open at a temperature at least
10°F below temperature setpoint for limit switch?
EXAMPLE: The setpoint is 220°F, but switch opens at a temperature below
210°F.
19
58
—
58.
The problem may be related to poor air distribution or excessive pressure drop
across filter. If pressure drop across filter is more than 0.3 in. wc, replace filter,
otherwise add turning vanes, more supply-air openings, or more return-air open-
ings. Use Appendix E to evaluate external static pressure.
—
—
27
59.
While unit is operating in low heat, jumper R and W2.
—
—
60
60.
Does furnace have a variable-speed ICM blower motor?
61
38
—
STEP
TERMINAL CONNECTIONS*
VOLTAGE
ACTION
61.
PL4-4
BROWN (+)
to
PL4-3
BLACK (-)
-7 vdc to -13 vdc
If voltages are correct, go to Step 62. If not, replace 2-stage
furnace control.
62.
PL9-13
BROWN (+)
to
PL9-3
BLACK (-)
-7 vdc to -13 vdc
If voltages are correct, go to Step 63. If not, repair or replace
ICM blower harness.
STEP
ACTION
YES
NO
GO TO
63.
Did blower motor change speed when R and W2 were jumpered?
38
35
—
* (+) and (-) designate Volt Ohm Meter Leads
Status Code 34
IGNITION-PROVING FAULT—THIS STATUS CODE INDICATES FLAME WAS NOT SENSED DURING TRIAL FOR IGNITION
PERIOD. THE CONTROL WILL REPEAT IGNITION SEQUENCE 3 MORE TIMES BEFORE GOING TO STATUS CODE
14—IGNITION LOCKOUT. THIS STATUS CODE CAN ALSO INDICATE FLAME SIGNAL WAS LOST DURING STEADY-STATE
OPERATION.
STEP
ACTION
YES
NO
GO TO
1.
Shut power off, remove blower door, and disconnect R thermostat lead from
furnace control board.
—
—
2
2.
Turn power on and depress door switch. Use a piece of tape to hold switch
closed.
—
—
3
3.
Jumper R and W/W1 thermostat terminals.
—
—
4
4.
Observe operation of furnace through 1 heating cycle.
—
—
5
5.
Does status code 34 flash?
9
6
—
6.
Does a different status code flash?
7
8
—
7.
Go to page number indicated in Index for section covering status code.
—
—
INDEX
8.
Go to page number indicated in Index for CLEANUP AND START-UP IN-
STRUCTIONS.
—
—
INDEX
9.
Turn off power and disconnect jumper across R and W/W1 thermostat termi-
nals.
—
—
10
10.
Turn power on.
—
—
11
11.
Check hot surface ignitor. To do this, run a COMPONENT TEST by shorting
TWIN/TEST terminal to C
OM
-24V thermostat terminal for 2 sec. Does ignitor
glow orange/white hot by end of 15-sec warm-up period?
16
12
—
12.
Hook an AC voltmeter across PL2-3 and PL2-9 on 2-stage furnace control. Re-
peat COMPONENT TEST by shorting TWIN/TEST terminal to C
OM
-24V thermo-
stat terminal for 2 sec. Do you have 115 vac across PL6-1 and PL6-2 during
15-sec warm-up period?
14
13
—
13.
Replace 2-stage furnace control.
—
—
8
14.
Check continuity in harness and ignitor. Replace failed component.
—
—
15
15.
Fix problem.
—
—
8
16.
Jumper R and W/W1 thermostat terminals.
—
—
17
17.
Do you have 24 vac across BLUE and GREEN wire to gas valve GV?
21
18
—
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