Replace
board.
Turn on
power to unit.
Is blower running?
NO
Jumper across screws R & G.
Is
blower running
on cooling
speed?
YES
Is
NO115VAC across
& COM?
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| START |
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| Disconnect all thermostat | |||
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| wires from board. |
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YES | Is 24VAC | YES | |||||
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| across screws |
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R & C?
NO
Check/Replace:
1.Limit switch
2.Limit shield (if used)
3.Fuse link
4.Auxillary limit switch (if used)
5.Wire harness
Is
NO115VACNO across HI &
COM?
YES
Replace
blower motor
and/or start
capacitor.
Is 24VAC | YES |
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across screws |
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W & C or |
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G & C? |
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| NO |
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Is
115VACYES across L1 &
L2?
NO
Check/Replace:
1.Unit power
2.Door switch
3.Power harness
Turn off
power to unit.
NO
Are
all thermostat wires to board disconnected?
YES
Replace
board.
YES
Is
24VAC
across screws
R & C?
NO
Check/Replace:
1.
2.Transformer
YES
Remove
R & G jumper.
Check pressure tube for leak or crimp; otherwise, replace pressure switch
YES
Is
24VAC
across
NO
NO | Replace | ||
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| board. |
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NODoes blower turn
off?
YES
Is heat
exchangerYES pressure drop greater 
than
wc?
NO
YES
Is 24VAC
across pressure
switch N/O contact
&screw C on board?
NO
Repair wire
harness.
Jumper across screws R & W.
Is
inducer motor
on?
NO
Check/Replace:
1.Vent systems
2.Induce wheel
3.Flue choke
4.Inducer voltage
5.Inducer motor bearings
YES | Is | NO |
| unit lit? |
|
YES
Is 24VAC
across pressure
switch N/O contact
&screw C on board?
NO
Is
24VAC across gas
valve?
YES | Check/Replace: | ||||
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| 1. | Draft safeguard switch | |
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| 2. | Wire harness | |
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YES | Check/Replace: | ||||
1. | Pilot | ||||
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| 2. | Thermocouple | |
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| 3. | Gas valve | |
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Replace
YES
Is
115VAC across
Is
blower running NO on heat speed 45
Is
115VAC across
YES | Replace | |
blower motor | ||
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inducer motor.
NO
Check/Repair wire harness; otherwise, replace pressure switch.
inducer motor
connector?
NO
Is
24VAC across
YES
Replace
board.
NO
sec after unit
lights?
YES
Is
115VAC
across
& COM?
YES
Remove
R & M jumper.
inducer motor
connector?
NO
Is
24VAC across
NO
Repair wire
harness.
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| and/or start | ||
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| capacitor. | ||
YES |
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| Replace |
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| board. |
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| Check/Replace |
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| thermostat |
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| and/or |
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| thermostat wiring. |
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NO
After
turn off?
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| NO |
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Reconnect all |
| Does unit | |
thermostat wires. |
| operate? | |
NOTE: After replacing any component, verify correct operating sequence as indicated by bold arrows.
YES |
END OF TEST. |
A91253
Copyright 1993 CARRIER Corp. · 7310 W. Morris St. · Indianapolis, IN 46231 | 35005c |
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Manufacturer reserves the right to discontinue, or change at any time, specifications or designs without notice and without incurring obligations.
Book | 1 | 4 | PC 101 | Catalog No. | Printed in U.S.A. | Form | Pg 8 | Replaces: | ||
| Tab | 6a | 8a |
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