A.O. Smith 185874-001, FMV-40, FMV-30, FMV-50 Troubleshooting Guidelines, Problem Cause Solution

TROUBLESHOOTING GUIDELINES

These guidelines should be utilized by a qualified service agent. When calling for service notify the service agent that this is a “Flammable Vapor Ignition Resistant” Product.

Problem	Cause	Solution
	Improperly sealed, hot or cold supply connection, relief valve,	Tighten threaded connections.
WATER LEAKS	drain valve, or thermostat threads.
	Leakage from other appliances or water lines.	Inspect other appliances near water heater.
	Condensation of flue products.	Refer to CONDENSATE.
	Thermal expansion in closed water system.	Install	thermal expansion tank	(DO	NOT	plug T&P
		valve).
LEAKING T&P VALVE
	Improperly seated valves.	Check relief valve for proper operation (DO NOT plug
		T&P valve.
SMELLY ODORS	High sulfate or mineral content in water supply.	Drain and flush heater thoroughly, then refill.
	Bacteria in water supply.	Chlorinate or aerate water supply.
	Gas control knob not positioned correctly.	Refer to LIGHTING INSTRUCTIONS.
	Main gas supply off.	Turn on main gas Shut-off valve.
	Igniter tip more than 1/8” from pilot hood.	Adjust ignitor tip.
	Thermocouple malfunction.	Replace pilot assembly.
PILOT WILL NOT LIGHT	Thermocouple TCO malfunction.	Replace pilot assembly.
	Melted insulation on ignitor wire or shorting of ignitor wire.	Contact a service agency to determine cause.
	High ambient room temperature.	Contact a service agency to determine cause.
	Wire disconnected from spark ignitor.	Reconnect wire connector to spark ignitor.
	Broken electrode or electrical wire.	Replace pilot assembly.
	Piezo ignitor generator fails to operate or malfunctions.	Replace Piezo ignitor generator.
	Thermocouple TCO malfunction.	Replace pilot assembly.
	High ambient room temperature.	Contact a service agency to determine cause.
BURNER WILL NOT STAY LIT
	Dirty or clogged air intake screen.	Clean and reinstall air intake screen.
	Flame arrestor openings blocked.	Contact a service agency to determine cause.
	Defective Gas Control.	Replace gas control.
	Dirty pilot burner.	Clean pilot assembly.
	Dirty or clogged air intake screen.	Clean and reinstall air intake screen.
PILOT OUTAGE	Thermocouple tip is not in contact with pilot flame.	Insert thermocouple correctly.
	Thermocouple malfunction.	Replace pilot assembly.
	Thermocouple TCO malfunction.	Replace pilot assembly.
	Defective Gas control.	Replace Gas Control.
	Heater not lit or thermostat not on.	Refer to LIGHTING INSTRUCTIONS.
	Thermostat set too low.	Refer to TEMPERATURE REGULATION.
	Heater undersized.	Reduce hot water use.
NOT ENOUGH HOT WATER	Low gas pressure.	Contact your gas supplier.
	Incoming water is unusually cold.	Allow more time for heater to re-heat.
	Leaking hot water pipes or fixtures.	Have plumber check and repair leaks.
	High temperature limit switch activated.	Contact a service agency to determine cause.
Water TOO HOT	Thermostat set too high.	Refer to TEMPERATURE REGULATION.
Water HEATER SOUNDS	Condensation dripping on burner.	Refer to CONDENSATE above.
SIZZLING-RUMBLING	Sediment or calcium in bottom of heater tank.	Clean	sediment from tank.	Refer	to	DRAINING
		instructions in Maintenance section of manual.
SOOTING		No adjustment available. Immediately shut down the
	Improper combustion.	water heater and contact a service agency to determine
		cause.
	Lack of supply air.
VENT GAS ODORS	Improperly installed vent piping.	Immediately shut down the water heater and contact a
	Downdraft.	service agency to determine cause.
	Poor combustion.

31