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All installations and services must be performed by qualified service personnel.
VII. 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
2 flashes, then pause
3 flashes, then pause
4 flashes, then pause
6 flashes, then pause
7 flashes, then pause
8 flashes, then pause
Continuous flashing
(no pause)
The LED will also flash once at power-up.
: Power must be disconnected before servicing.
System lockout
Pressure switch stuck closed
Pressure switch stuck open
Open limit switch or rollout switch
115 Volt AC power reversed
Low flame sense signal
Check ignitor or improper grounding
Flame has been sensed when
no flame should be present
(no call for heat)
41
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