Detroit Radiant Products Company FA Series - Manual (Page 43)

43
FA Series
Bypassing any switch is intended for testing purposes only. Do not leave switch bypassed
during normal operation or the heater’s built-in safety mechanisms will be compromised. NOTICE
4.0 Troubleshooting Guide
Key
Start
Question
Process
Question
Corrective
Action
Is there 24 VAC
across the ‘R’ and
‘C’ terminals?
Check fuse on circuit board and
internal controls transformer.
After approx.
10 seconds of
operation, is there
a flash code for
‘Pressure Switch
Failure’?
Replace pressure switch after verifying:
• Heater, blower, and venting are clean and
free of obstructions.
• The allowable vent length is not
exceeded.
• There is not a negative pressure
experienced at the area of intake (e.g.,
high winds, attic space, tightly sealed
building).
Replace
circuit board.
Monitor the voltage on
the gas valve terminals
during trial for ignition.
Is there 24 VAC present
during the spark
sequence?
Yes
Gas valve is faulty.
Replace.
No
Yes
Is there 24 VAC
across the ‘W’
and ‘C’ terminals?
Yes
Is the circuit board
sending 120 VAC
to the draft inducer
motor?
Yes
Is the draft
inducer impeller
obstructed or
locked up?
Remove
obstruction.
No
The draft inducer motor is
faulty and must be replaced.
Yes
No
Is the pressure
switch stuck in the
closed position?
Pressure switch is faulty.
No
Yes
Check the
two flame roll
out switches
and the tube
temperature
limit switch. Are
they closed?
Yes
Reset or replace
faulty limit switch.
No
Replace circuit board.
Check for flash
codes on the circuit
board. Replace the
ignition module.
No
No
No
Yes
Repair thermostat or
thermostat wiring.