Friedrich SM21L30-A, Service Manual

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16
COOLING ONLY ROOM AIR CONDITIONERS: TROUBLESHOOTING TIPS
Problem Possible Cause Action
Compressor
does not run
Low voltage
Check voltage at compressor. 115V & 230V
units will operate at 10% voltage variance
T-stat not set cold enough or inop-
erative Set t-stat to coldest position. Test t-stat &
replace if inoperative
Compressor hums but cuts off on
B10 overload Hard start compressor. Direct test compressor.
If compressor starts, add starting components
Open or shorted compressor wind-
ings
Check for continuity & resistance
Open overload Test overload protector & replace if inoperative
Open capacitor Test capacitor & replace if inoperative
Inoperative system switch
Test for continuity in all positions. Replace if
inoperative
Broken, loose or incorrect wiring
Refer to appropriate wiring diagrams to check
wiring
Problem Possible Cause Action
Fan motor
does not run
Inoperative system switch Test switch & replace if inoperative
Broken, loose or incorrect wiring Refer to applicable wiring diagram
Open capacitor Test capacitor & replace if inoperative
Fan speed switch open Test switch & replace if inoperative
Inoperative fan motor
Test fan motor & replace if inoperative (be sure
internal overload has had time to reset)
Problem Possible Cause Action
Does not cool or
only cools slightly
Undersized unit Refer to industry standard sizing chart
T-stat open or inoperative
Set to coldest position. Test t-stat & replace if
necessary
Dirty fi lter Clean as recommended in Owner's Manual
Dirty or restricted condenser or
evaporator coil Use pressure wash or biodegradable cleaning
agent to clean
Poor air circulation Adjust discharge louvers. Use high fan speed
Fresh air or exhaust air door open
on applicable models Close doors. Instruct customer on use of this
feature
Low capacity - undercharge Check for leak & make repair
Compressor not pumping properly
Check amperage draw against nameplate. If
not conclusive, make pressure test