Friedrich YL24J35A, Service & Parts Manual

Page: 32 / 62

TTJ-0198 (10/97) (Page 32 of 64)
PROBLEM POSSIBLE CAUSE TO CORRECT
Troubleshooting Heating (Continued)
(Heat Pumps)
Incorrect Wiring
Defrost control timer motor not
advancing.
Defrost control out of calibration.
Defrost control contacts stuck.
Defrost control bulb removed from
coil, or not making good coil contact.
Refer to appropriate wiring diagram.
Check for voltage at "TM" and "TM1" on
timer. If voltage, replace control.
If outside coil temperature is 25
°
F or below,
and preselected time limit has elapsed,
replace defrost control.
If contacts remain closed between terminals
"2" and "3" of the defrost control after
preselected time interval has passed, replace
control.
Reinstall and be assured that good bulb to
coil contact is made.
Unit will not defrost.
Unit does not heat
adequately.
Outdoor thermostat does not cut off
compressor at the preselected tem-
perature and bring on heating element.
Fresh air or exhaust door open.
Dirty filter.
Unit undersized.
Defective thermostat - replace.
Check if operating properly. Instruct customer
on proper use of control.
Clean as recommended in Owner’s Manual.
Check heat rise across coil. Refer to perfor-
mance data sheet on heat rise at various
outdoor ambients. If heat rise is satisfactory,
check if insulation can be added to attic or
walls.
PROBLEM POSSIBLE CAUSE TO CORRECT
Refer to applicable wiring diagram.
Check for continuity of coil.
Block condenser coil and switch unit to cooling.
Allow pressure to build u p in system, then
switch to heating. If valve fails to shift, replace
valve.
Check for continuity of system switch.
Unit cools when
heat is called for.
Incorrect wiring.
Defective solenoid coil.
Reversing valve fails to shift.
Inoperative system switch.
PROBLEM POSSIBLE CAUSE TO CORRECT