York ZF 180 Series Installation Manual page 47

The pilot burner lights and the spark stops but the main burners
do not light.
1. Check electrical connections between the ignitor control
and the gas valve. If intact, check for 24 volts across
terminals "MV" and "COMMON" terminals. If no voltage
detected, replace ignitor control. If voltage is present,
replace gas valve.
Furnace lights with roll-out or one burner has delayed ignition.
1. Make sure that the pilot burner is aligned properly with the
carryover as described in "PILOT CHECKOUT" page 41.
2. Make sure that the carryovers on adjoining burners are
screwed fast and are level with respect to one another.
Main burners light but exhibit erratic flame characteristics.
1. Adjust air shutters as described in "BURNER AIR
SHUTTER ADJUSTMENT" page 41.
2. Check the main burner orifices for obstruction and
alignment. Removal procedure is described in BURNER
INSTRUCTIONS page 41. Clean or replace burner orifices
and burners as needed.
Unit Control Board Flash Codes
Various flash codes are utilized by the unit control board (UCB)
to aid in troubleshooting. Flash codes are distinguished by the
Johnson Controls Unitary Products
short on and off cycle used (approximately 200ms on and
200ms off). To show normal operation, the control board
flashes a 1 second on, 1 second off "heartbeat" during normal
operation. This is to verify that the UCB is functioning correctly.
Do not confuse this with an error flash code. To prevent
confusion, a 1-flash, flash code is not used.
Alarm condition codes are flashed on the UCB lower left Red
LED, See Figure 32. While the alarm code is being flashed, it
will also be shown by the other LEDs: lit continuously while the
alarm is being flashed. The total of the continuously lit LEDs
equates to the number of flashes, and is shown in the table.
Pressing and releasing the LAST ERROR button on the UCB
can check the alarm history. The UCB will cycle through the last
five (5) alarms, most recent to oldest, separating each alarm
flash code by approximately 2 seconds. Flash code 21 is a non-
alarm condition but due to the space constraints of the UCB,
will be indicated by the Red LED. In all other cases, a flashing
Green LED will be used to indicate non-alarm conditions.
In some cases, it may be necessary to "zero" the ASCD for the
compressors in order to perform troubleshooting. To reset all
ASCDs for one cycle, press and release the UCB TEST/
RESET button once.
Flash codes that do and do not represent alarms are listed in
Table 31.
1061903-XIM-A-0713
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