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6.8.3 Troubleshooting the 24 VAC Circuit in FBRA18 Units (Continued)
NOTE: All voltage measurements involving the
gas valve leg of the 24V circuit 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.
A
Is 24VAC
present on N/O
terminal of latch
relay?
Is 24VAC
present on COM
terminal of latch
relay?
Is 24VAC
present on J1 pin
3?
When water level
is above lower water level
sensor, is CYCLE LED lit?
Go to
"B".
Go to
"C".
Probable causes are failed
wiring between terminal block
and computer, or failed
computer.
If 12VDC is applied across coil,
probable cause is failed relay. If not,
probable cause is failed wiring between
controller and latch relay or failed
controller.
Probable causes are failed
24V transformer or failed wiring
between transformer box and
component box.
Yes
No
Yes
No
Yes
No
Yes
No