Thermo Products GMC-85, OMC-70 service manual Omc/Gmc Troubleshooting Flowchart

All installations and services must be performed by qualified service personnel.

OMC/GMC TROUBLESHOOTING FLOWCHART

Set thermostat subbase to "HEAT"

Does thermostat make contact?

	No
Is room temperature		Yes
			Wait for room air to cool.
above 90 deg. F?

Yes	No
	Yes

Is room temperature above	Turn thermostat setting
thermostat setting?	above room temp.

No

Replace thermostat

Does a "call for heat" initiate an ignition cycle?

Yes

No			Yes
	Is the power switch "off"?				Turn power
					switch "on".
		No
			No
				Check input power. Reset circiut
	Is there 120 VAC
				breaker, or replace blown fuse in
	across lines L1 & L2?
				disconnected switch.

Yes				Wait for furnace to cool.
Is the control transformer	No	Have either of the	Yes	Look for cause(s) of high
				limit activation,eg. low
(GMC) or oil primary control		high limit thermostats
				airflow, over-firing,
(OMC) receiving 120 VAC?		activated?
				blocked flue,etc..
				Correct any
				abnormal conditions.
Yes		No
		With power on,measure
		voltage across the aux.
		high limit thermostat N.C.
		contact to L2. If not 120 VAC,
		replace aux. high limit
		thermostat. Else,replace
		high limit thermostat.

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