Troubleshoot

BEFORE REPLACING THE CONTROL BOARD
• Remove thermostat and use a temporary jumper wire to make a call for heat
• Check the supply power for correct polarity
• Recheck all wiring to the control board for loose connections. Disconnect and reconnect all Molex plugs
• Recheck that the wiring to the control board matches the wiring diagram
• If the control board has a fuse, remove and test continuity of the fuse. Do not just do a visual inspection
of the fuse - check continuity
• Make sure the pressure switch is not opening during the call for heat cycle
• Check limits and rollout switches for an open circuit
• Turn the switch on the gas valve to off and then to on several times
• Make sure power inducer is running when there is a call for heat
• Check for a proper micro amp signal from the flame sensor to the control board. A proper signal is 1-5
micro-amps
• Check for proper supply gas pressure. Excessive gas pressure can/will lockup the main valve
• Check for limit and/or flame sensor shorts (make sure they are not touching metal)
• Check for any moisture on board that may have occurred if checking for gas leaks with a liquid solution.
• Check in-line regulators for BTU sizing, and lock up point not above a 14” WC.
• Check setting of heat anticipator of t stat if applicable, and wire size and run
• Review troubleshooting codes.
• Check for any moisture or moisture marks on the board that may have occurred if checking for gas leaks
with liquid solution.
• Check in-line regulators for BTU sizing and lock up point not above a 14" WC
• Check to make sure external regulator is not right next to the unit so that the regulator "fights" the
• regulator inside the combination gas valve.
• Check setting of heat anticipator of T-Stat if applicable, also check wire size and run length
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