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All installations and services must be performed by qualified service personnel.
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VI. TROUBLESHOOTING
NOTICE: BEFORE TROUBLESHOOTING, FAMILIARIZE YOURSELF WITH THE START UP AND
CHECKOUT PROCEDURE.
ALL INSTALLATION AND SERVICES MUST BE PERFORMED BY QUALIFIED HEATING
CONTRACTORS.
To assist you in troubleshooting this furnace, it is equipped with an integrated ignition control with diagnostics.
These diagnostics evaluate what control system has experienced a failure and will activate a flashing light on the
control in different sequences to help pinpoint the failure which has occurred.
IMPORTANT: For your convenience, Thermo Products has installed a sight glass in the blower door of this
furnace. The number of flashes in groups should be observed through this sight glass and recorded before turning off
power to the furnace. Otherwise power to the furnace will be when turning off power or removing the blower door
which is equipped with door interlock switch, which will reset the control. Should this occur, it will be necessary to
restart the furnace and have the failure occur again.
DIAGNOSTIC FEATURES
The 50A65 control continuously monitors its own operation and the operation of the system. If a failure occurs, the
LED will indicate a failure code as shown below. If the failure is internal to the control, the light will stay on
continuously. In the case, the entire control should be replaced, as the control is not field-repairable.
If the sensed failure is in the system (external to the control), the LED will flash in the following flash-pause
sequences to indicate failure status (each flash will last approximately 0.25 seconds, and each pause will last
approximately 2 seconds).
1 flash, then pause System lockout
2 flashes, then pause Pressure switch stuck closed
3 flashes, then pause Pressure switch stuck open
4 flashes, then pause Open limit switch or rollout switch
6 flashes, then pause 115 Volt AC power reversed
7 flashes, then pause Low flame sense signal
8 flashes, then pause Check ignitor or improper grounding
Continuous flashing Flame has been sensed when
(no pause) no flame should be present
(no call for heat)
The LED will also flash once at power-up.
: Power must be disconnected before servicing.