ICP 9MAC/E series Troubleshooting manual - Status Code 4 + 3
- 36 -
STEP
ACTION
YES
NO
GO TO
61.
Does a different status code flash?
7
65
62.
Is there any frost build-up on combustion-air inlet?
63
64
63.
The problem is caused by reversed vent and combustion-air pipes or some other moist air
entering combustion-air pipe.
15
64.
You have excessive restriction in combustion-air or vent pipe. Also check for proper vent
sizing for installation.
15
65.
While the unit is operating in minimum heat jumper R and W2.
66
66.
Observe the operation of the furnace for the next 8 minutes or until fault occurs.
67
67.
Does status code 4 + 2 flash?
25
68
68.
Does a different status code flash?
7
8
Status Code 4 + 3
LOW OR MEDIUM PRESSURE SWITCH OPEN WHILE MEDIUM OR HIGH PRESSURE SWITCH IS CLOSED - This status code
can occur as a result of the low pressure switch LPS not making during a call for heat. Keep in mind that whenever status
code 4 + 3 occurs the modulating furnace control shuts unit down, turns the inducer off, and gas remains off.
- INTERMEDIATE, OR MAXIMUM HEAT
1. PREPURGE - If the medium pressure switch MPS makes and the low pressure switch LPS is still open the modulating furnace control
starts flashing status code 4 + 3, shuts unit down, and waits 2 minutes before restarting the heating cycle. Same goes if the high pressure
switch HPS makes and the medium pressure switch MPS is still open.
STEP
ACTION
YES
NO
GO TO
1.
Turn power off, remove the blower door and disconnect communication connector PL7 (if
used) or the R thermostat lead (if used) from the furnace control board.
2
2.
Turn the power on and depress the door switch. Use a piece of tape to hold switch closed.
3
3.
Jumper the R and W/W1 thermostat terminals.
4
4.
Observe the operation of the furnace until ignition.
5
5.
Does status code 4 + 3 flash?
9
6
6.
Does a different status code flash?
7
8
7.
Go to page number indicated in the Index for the section covering the status code.
INDEX
8.
Go to page number Indicated in Index for CLEANUP AND START-UP INSTRUCTIONS.
INDEX
9.
Are the pressure switches wired correctly?
11
10
10.
Fix problem.
8
11.
Is 24-vac across YELLOW wire on the low pressure switch LPS and C
OM
-24V on
modulating furnace control?
14
12
12.
Is 24-vac across connector terminal PL1-2 and C
OM
-24V on modulating furnace control?
13
18
13.
You have an open wire or bad terminal on the YELLOW wire from the modulating furnace
control to the low pressure switch LPS. Repair it or replace the harness.
8
14.
Is 24-vac across ORANGE wire on the low pressure switch LPS and C
OM
-24V on
modulating furnace control?
Note:
You may need to wait a few minutes for the modulating furnace control to ramp the
inducer motor back up to speed.
15
19
15.
Is 24-vac across connector terminal PL1-4 and C
OM
-24V on modulating furnace control?
20
16
16.
Turn power off and disconnect jumper wire across R and W/W1 thermostat terminals.
17
17.
You have an open circuit between the low pressure switch LPS and the modulating furnace
control. This includes all the ORANGE wires interconnecting the low pressure switch LPS
to the modulating furnace control. It also includes the low gas pressure switch LGPS (if
used).
Check the continuity across the low gas pressure switch LGPS (if used). If there is no
continuity check the propane line pressure. If the propane line pressure is correct replace the
low gas pressure switch LGPS.
Check the continuity of each ORANGE wire interconnecting the low pressure switch LPS
and the modulating furnace control. Repair open wire or replace harness.
8
18.
Replace the modulating furnace control.
8
19.
Replace the pressure switch assembly.
8
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