Friedrich 2009, 2008 service manual Heat Pump Troubleshooting

HEAT PUMP TROUBLESHOOTING

Problem	Possible Cause	Action
		Disconnect power to unit. Remove resistor
	Heat anticipator (resistor) shorted	from t-stat bulb block. Plus in unit & allow to
	(on applicable models)	operate. Feel resistor for heat. If not heat,
Room		replace resistor
temperature	Wide differential - partial loss of	Replace t-stat & check
uneven	t-stat bulb charge
(Heating cycle)		Refer to appropriate wiring diagram. Resistor
	Incorrect wiring	is energized during “ON” cycle of compressor
		or fan.
	Defective thermistor or control board	Replace thermistor or electronic control board

Problem	Possible Cause	Action
	Incorrect wiring	Refer to appropriate wiring diagram
	Defrost control out of calibration	If outside coil temperature is 25°F or below,
		& preselected time limit has elapsed, replace
	(applicable models)
		defrost control
Unit will not		If contacts remain closed between terminals
	Defrost control contacts stuck	“2” & “3” of the defrost control after
defrost
		preselected time interval has passed, replace
		control
	Defrost control bulb removed from	Reinstall & be assured that good bulb to coil
	or not making good coil contact	contact is made
	Outdoor coil thermistor	Replace thermistor or electronic control board

Problem	Possible Cause	Action
	Dirty filter	Clean as recommended in Owner’s Manual
		Check heat rise across coil. If unit operates
	Unit undersized	efficiently, check if insulation can be added
		to attic or walls. If insulation is adequate,
		recommend additional unit or larger one
Does not heat	Outdoor t-stat open (applicable	T-stat should close at 38°F. Check continuity
		of control. If temperature is below 38°F,
	models)
adequately		replace control
	Heater hi-limit control cycling on &	Check for adequate fan air across heater.
		Check control for open at 160°F & close at
	off
		150°F
	Shorted supplementary heater	Ohmmeter check, approx. 32-35 ohms
	Incorrect wiring	Check applicable wiring diagram
	Defective thermistor or electronic	Replace thermistor or electronic control board
	control board

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