Manual 2100-587DPage 35 of 5828. SERVICE AGENCY PROCEDURESMain BurnerObserve the main burners in operation. The flameshould be mostly “blue” with possibly a little orange(not yellow) at the tips of the flame. The flames shouldbe in the center of the heat exchanger tubes and notimpinging on the heat exchanger surfaces themselves.Observe the fire until the blower starts (there is anormal delay period until the heat exchanger warmsup). There should be no change in the size or shapeof the flame. If there is any wavering or blowing ofthe flame on blower start-up, it is an indication of apossible leak in the heat exchanger.Burners/Heat Exchanger/Flue Gas Passage WaysThe burners, heat exchanger and interior flue gaspassages may be inspected using a light on smallmirror or an extension handle. Remove the screwssecuring the inducer and collector box. Now inspectthe upper tubes of the heat exchanger.Check the exterior of the heat exchanger andthe interior flue gas passages for any evidence ofdeterioration due to corrosion, cracking or other causes.If signs of sooting exist, remove the burners and cleanthe heat exchanger, as required.29. MAINTAINING UNIT IN GOODWORKING ORDERThe unit should be inspected annually by a qualifiedservice agency.FIGURE 15Top View of Gas ControlCAUTIONLabel all wires prior to disconnection whenservicing controls. Wiring errors can causeimproper and dangerous operation. Verifyproper operation after servicing.WARNINGFollow these procedures before inspectingfurnace.• Turn room thermostat to its lowest or offsetting.• Turn off manual gas shut off valve.• Wait at least 5 minutes for furnace to cool ifit was recently operating.• Turn off furnace electrical power; failure todo so could result in injury or death.WARNINGUse replacement parts listed in theReplacement Parts list only. The use ofincorrect parts could cause improper unitoperation, resulting in damage, injury or death.MIS-165