ICP 9MAC/E series Troubleshooting manual - Status Code 8
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Status Code 8
GAS HEATING LOCKOUT - This status code indicates the gas valve relay GVR on the modulating furnace control is stuck
closed or there is a miswire/short to gas valve BLUE wire. The modulating furnace control will NOT auto-reset.
STEP
ACTION
YES
NO
GO TO
1.
Remove blower door. Disconnect communication connector PL7 (if used) or the R
thermostat lead (if used) from the furnace control board. Depress door switch.
2
2.
Does status code 8 flash?
3
6
3.
There is a miswire or short to the gas valve BLUE wire.
4
4.
Fix problem
5
5.
Go to page number indicated in Index for CLEANUP AND START-UP INSTRUCTIONS.
INDEX
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.
Use a piece of tape to hold door switch closed.
9
9.
Jumper R and W/W1 thermostat terminals.
10
10.
Does status code 8 start flashing when the low pressure switch LPS makes?
11
12
11.
Replace the modulating furnace control.
5
12.
Does a different status code flash?
7
13
13.
Disconnect the jumper wire across R and W/W1 thermostat terminals and wait until the
blower stops.
14
14.
Cycle the furnace several times to check for intermittent operation.
15
15.
Does status code 8 ever flash?
11
16
16.
Go to page number indicated in Index for CLEANUP AND START-UP INSTRUCTIONS.
If the problem persists on an intermittent basis, replace the modulating furnace control. If
problem still persists on an intermittent basis after replacing the modulating furnace control,
contact your distributor.
INDEX
Status Code 9
MEDIUM PRESSURE SWITCH, HIGH PRESSURE SWITCH, OR PSR RELAY DID NOT CLOSE OR REOPENED - This status
code can occur under the scenarios shown below. Keep in mind that whenever the modulating furnace control shuts unit
down, gas remains off or shuts off immediately, inducer continues running for 15 seconds, and if the blower is running, it
remains running at minimum heat airflow or reduces to minimum heat airflow for the selected off-delay.
- LOW RANGE INPUT OPERATION (40% - 51% OF MAXIMUM HEAT, 40% - 45% OF MAXIMUM HEAT ON 5T-060)
1. STEADY-STATE - If the medium pressure switch input turns ON the modulating furnace control begins flashing status code 9 and
continues to operate at the current low range input. After the call for heat is satisfied and the blower off-delay is completed the control will
stop displaying status code 9.
- MEDIUM RANGE INPUT OPERATION (52% - 71% OF MAXIMUM HEAT, 46% - 71% OF MAXIMUM HEAT ON 5T-060)
1. PREPURGE - If the medium pressure switch MPS does not make within 45 seconds after the low pressure switch LPS made the
modulating furnace control begins flashing status code 9, shuts unit down, waits 2 minutes, stops flashing status code 9, and restarts
heating cycle.
If medium pressure switch MPS opens before ignition, the modulating furnace control ramps inducer RPM up until the medium pressure
switch MPS remakes. When the medium pressure switch MPS remakes the modulating furnace control continues the heating cycle. If
medium pressure switch MPS does not remake within 45 sec after opening, the modulating furnace control starts flashing status code 9,
shuts unit down, waits 2 minutes, stops flashing status code 9, and restarts heating cycle.
2. LOW TO MEDIUM RANGE INPUT TRANSITION - If the medium pressure switch MPS fails to make within 45 seconds after a
medium range input was requested the modulating furnace control shuts unit down and begins flashing status code 9. After the blower off-
delay is completed the modulating furnace control will stop displaying status code 9 and if there is a call for heat, begin a new heating
cycle.
3. STEADY-STATE - If the medium pressure switch MPS opens the modulating furnace control ramps inducer RPM up until the medium
pressure switch MPS remakes. When the medium pressure switch MPS remakes the modulating furnace control continues the heating
cycle. If medium pressure switch MPS does not remake within 45 sec after opening, the modulating furnace control starts flashing status
code 9 and shuts the unit down. After the blower off-delay is completed the modulating furnace control will stop displaying status code 9
and if there is a call for heat, begin a new heating cycle.
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