6.8.3 Troubleshooting the 24 VAC Circuit in FBRA18 Units (Continued)
B
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.
Is 24VAC
present across the gas Yes valve main coil (PV)
terminal?
No
Gas valve leg of 24V circuit is OK.
Is
24VAC present on
VALVE terminal of LEFT Yes ignition module?
Probable cause is
failed wiring between module and gas valve.
No
Is 24VAC present | Yes | If fuse is not | |
on 25V terminal of LEFT | blown, module | ||
| |||
ignition module? |
| has failed. | |
No |
|
| |
|
| No |
Is 24VAC
present on J2 Yes pin 4?
Is 24VAC present
on 25V terminal of RIGHT Yes ignition module?
Is
24VAC present on
VALVE terminal of RIGHT
ignition module?
No
No | Yes |
Is 24VAC
present on J2 Yes pin 3?
No
Probable cause is
failed wiring between terminal block and J2 pin 3.
Probable causes are failed | Probable cause |
wiring between blower centrifugal | |
switch and module, failed | is failed wiring |
centrifugal switch, or failed | harness. |
wiring harness. |
|
Probable cause |
|
is failed CYCLE |
|
relay. |
|
