6.8.3 Troubleshooting the 24 VAC Circuit in FBRA18 Units (Continued)
C
NOTE: All voltage measurements must be made within 4 seconds of unit calling for heat. If unit does not fire within 4 seconds, ignition modules will lock out and controller must be turned off then back on to reset.
Is 24VAC
present on J1 pin 5 Yes when unit calls for
heat?
No
Is 24VAC
present on N/O Yes terminal of 12VDC
relay?
No
Probable cause is failed wiring between latch relay and 12VDC relay.
Is J1 pin 2 | Yes |
grounded? |
|
No |
|
Clean lower water level sensor and ground it.
Does
CYCLE LED light No when unit calls for
heat?
Yes
Go to
"B".
Is 24VAC
present on COM
terminal of 12VDC relay Yes 
when unit calls for
heat?
No
Is
12VDC present
across coil of 12VDC relay Yes when unit calls for
heat?
No
Probable cause is
failed controller wiring
harness or failed
controller.
Probable cause is failed interface board.
Probable cause is failed wiring between relay and interface board.
Probable cause is failed 12VDC relay.
