Troubleshooting: Heating (Heat pumps)

PROBLEM

POSSIBLE CAUSE

TO CORRECT

 

 

 

 

 

 

 

Thermostat setting.

Set thermostat to a warmer position.

No heating — fan

Defective thermostat.

Replace — do not attempt to adjust.

operates.

Compressor not operating.

Check compressor wiring. Check for open internal

 

 

or external overload. Check wiring.

 

Defective system switch.

Test system switch

PROBLEM

POSSIBLE CAUSE

TO CORRECT

 

 

 

 

Restricted filter.

Clean as recommended in Owner’s Manual.

Insufficient heating.

Outdoor thermostat.

Check if outdoor thermostat is energizing the heating

(Applicable models.)

element at its predetermined temperature setting

 

 

 

Check control setting.

 

Fresh air or exhaust door open.

 

PROBLEM

POSSIBLE CAUSE

TO CORRECT

 

 

 

Fan operates in

Inoperative system switch.

Check continuity of switch.

"constant" position, but

 

 

Incorrect wiring.

Check applicable wiring diagram.

not in "automatic"

(MoneySaver).

 

 

 

 

 

PROBLEM

POSSIBLE CAUSE

TO CORRECT

 

 

 

 

Temperature varies from

Defective thermostat.

Incorrect differential setting. Replace thermostat.

Heat anticipator (resistor) shorted.

Check voltage to resistor. If voltage okay, remove

comfortable to overly

(Applicable models)

resistor from thermostat bulb block. With current on,

warm.

 

feel resistor for warmth. If no heat can be felt,

 

 

replace anticipator.

PROBLEM

POSSIBLE CAUSE

TO CORRECT

 

 

 

 

Heat anticipator (resistor) shorted.

Disconnect power to unit. Remove resistor from

 

(Applicable models.)

thermostat bulb block. Plug in unit and allow to

Room temperature

 

operate. Feel resistor for heat. If no heat is felt,

uneven.

 

replace resistor.

(Heating cycle)

Wide differential — partial loss of ther-

Replace thermostat and check.

 

mostat bulb charge.

 

 

Incorrect wiring.

Refer to appropriate wiring diagram. Resistor is

 

 

energized during the "on" cycle of compressor or

 

 

fan.

PROBLEM

POSSIBLE CAUSE

TO CORRECT

 

 

 

 

Incorrect wiring.

Refer to appropriate wiring diagram.

 

Defrost control timer motor not advanc-

Check for voltage at "TM" and "TM1" on timer. If

Unit will not defrost.

ing.

voltage, replace control.

Defrost control out of calibration.

If outside coil temperature is 25° F or below, and

 

 

 

preselected time limit has elapsed, replace the

 

 

defrost control.

 

Defrost control contacts stuck.

If the contacts remain closed between terminals "2"

 

 

and "3" of the defrost control after preselected time

 

 

interval has passed, replace control.

 

Defrost control bulb removed from coil,

Reinstall and assure that good bulb to coil contact is

 

or not making good coil contact.

made.

 

 

 

40

Page 40
Image 40
Friedrich 2003 service manual Troubleshooting Heating Heat pumps