Fault code 43 – Carrier 58MVP User Manual
Page 30
43.
If possible, replace inducer wheel. Otherwise, replace inducer motor assembly.
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8
44.
Is there any frost build-up on combustion-air inlet?
45
46
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45.
The problem is caused by reversed vent and combustion-air pipes or some other moist air entering
combustion-air pipe.
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14
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46.
You have inadequate combustion-air supply. This may be caused by:
- Excessive restriction in combustion-air or vent pipe.
- Internal restriction in coupling box or secondary heat exchangers
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14
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47.
Replace pressure switch assembly.
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70
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48.
Is unit a trophy unit?
50
49
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49.
Does fault occur before blower motor turns ON?
47
51
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50.
Replace pressure switch assembly with pressure switch assembly used in NON-trophy models or
replace furnace control board. If you replace furnace control board make sure replacement control
has a date code of 9837 or later. Only replace the pressure switch assembly or the furnace control
board NOT both.
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70
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51.
Replace furnace control board.
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70
52.
Turn power off and disconnect jumper wire across R and W/W1 thermostat terminals.
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53
53.
Turn power on and wait several sec before proceeding to next step.
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54
54.
Disconnect collector box tube to pressure switch assembly.
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55
55.
Jumper R and W/W1 thermostat terminals on furnace control board.
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56
56.
Does Fault Code 42 occur within 11 sec after a call for heat?
57
58
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57.
Reconnect collector box tube to pressure switch assembly.
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10
58.
Reconnect collector box tube to pressure switch assembly.
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36
59.
Go to page number indicated in Index for CLEANUP AND STARTUP INSTRUCTIONS. If problem
persists on an intermittent basis, contact your distributor.
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INDEX
60.
Turn power off and disconnect jumper wire across R and W/W1 thermostat terminals.
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61
61.
Turn power on and wait several sec, then jumper R, W/W1, and W2 thermostat terminals on fur-
nace control board.
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62
62.
Does fault occur a few sec after high-pressure switch HPS makes?
NOTE: Check for 24v between the N.O. (Normally Open) contact on high-pressure switch
HPS and Com on furnace control board to know when high-pressure switch HPS makes.
63
67
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63.
Turn power off and disconnect jumper wire across R, W/W1, and W2 thermostat terminals.
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64
64.
Connect 1 side of a slope manometer with a tee to collector box pressure tap. Connect other side
with a tee to gas valve air pressure fitting. Refer to pressure check diagram in Appendix C.
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65
65.
Turn power on and wait several sec, then jumper R, W/W1, and W2 thermostat terminals on fur-
nace control board.
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66
66.
Do you have more than 1.9 in. wc pressure drop across heat exchangers when high-pressure
switch HPS makes?
NOTE: Check for 24v between the N.O. (Normally Open) contact on high-pressure switch
HPS and Com on furnace control board to know when high-pressure switch HPS makes.
47
44
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67.
Does fault occur a few sec after main burners ignite?
63
68
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68.
Observe operation of furnace in high heat for next 8 minutes or until fault occurs.
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69
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69.
Does the fault occur?
22
59
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70.
If problem still persists check for internal restriction in coupling box or secondary heat exchangers.
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14
Fault Code 43
PRESSURE SWITCH CALIBRATION FAULT—Indicates low-pressure switch LPS and high-pressure switch
HPS "make" points during high-heat purge are not within calibration range. This is determined by reading
inducer motor RPM when low-pressure switch LPS and high-pressure switch HPS make. Then the following
comparison is made:
0.55
‹
RPM (low)
RPM (high)
‹
0.90
If this relationship is not within range specified, furnace control board starts flashing fault colde 43, shuts unit
down (inducer runs for 15 sec), waits 2 minutes, stops flashing fault code, and restarts heating cycle.
It can also indicate that the high-pressure switch HPS made before the low-pressure switch LPS during either
low-heat or high-heat purge.
STEP
ACTION
YES
NO
GO TO
1.
Turn power off, remove blower access panel, and disconnect all thermostat leads from furnace con-
trol board.
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2
2.
Turn power on and depress door switch. Use a piece of tape to hold switch closed.
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3
3.
Jumper R, W/W1, and W2 thermostat terminals on furnace control board.
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4
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