The following procedure is used for troubleshooting & maintaining evaporator coils. It is recommended that evaporator coil(s) should be checked and cleaned every 100 hours of operation to keep the system operating at peak efficiency

TROUBLESHOOTING
Tools & Equipment
Part Description Source
Refrigerant recovery cart or pressure gauges Commonly Available
Electronic leak detector Commonly Available
Multimeter w/ clamp on amp meter Commonly Available
Vacuum Cleaner Commonly Available
Coil Cleaner (non acid) Commonly Available
Fin Comb Commonly Available


Install pressure gauges & turn system on

 
Trouble
Probable Cause
Correction
  Evaporator fan does not operate
A)
Worn brushes/bearings
A)
Motor needs overhaul or replacement
   
B)
Faulcty circuit breaker or fuse
B)
Re-cycle circuit breaker, replace fuse, replace circuit breaker
   
C)
Wiring problems
C)
Wring out wiring, check ground strap
  Evaporator fan trips circuit breaker, test only in the installed condition
A)
Worn brushes/bearings
A)
Motor needs overhaul
 
B)
Wiring problems
B)
Wring out wiring, check ground strap
   
C)
Faculty circuit breaker
C)
Replace circuit breaker
  Low evaporator air flow
A)
Dirty coil
A)
Clean coil
   
B)
Debris in the ducts
B)
Clean duct
  Irregular cooling, system runs cool & warm. Pressures oscillations up to 6 psi
A)
Moisture in system
A)
Service system, replace receiver drier bottle, repeat twice
  Insufficient cooling
A)
Restricted refrigerat flow
A)
Check plumbing for kinks & replace receiver drier bottle
   
B)
Low refrigerant level, too much oil in system, air in system
B)
Service system
   
C)
Blocked or faulty expansion valve
C)
Replace expansion valve
  Evaporator freezing
A)
Low refrigerant level
A)
Service system
   
B)
Expansion valve is faulty
B)
Replace expansion valve
   
C)
Blocked air flow
C)
Clean coil& ducts
   
D)
Faulty freeze switch, if equipped
D)
Replace freeze switch
  Evaporator leaking water from coil or ducts 
A)
Clogged or kinked drain tube
A)
Clean or replace tube
 
B)
Cracked coil housing
B)
Replace evaporator
 
COIL MAINTENANCE
Tools & Equipment
Part Description Source
Vacuum Cleaner Commonly Available
Coil Cleaner (non acid) Commonly Available
Fin Comb Commonly Available


Coil Cleaning Procedure
1)
 
Use vacuum cleaner to remove large debris from upstream and downstream coil faces.
2)
 
Check coil face for damage to tubes and fins. Comb damaged fins, replace evaporator if tubes are crushed or damaged.
3)
 
Spray coil cleaner on both coil faces. Wash off with water.
4)
 
Allow coil to dry thoroughly prior to additional maintenance.

 

EXPANSION VALVE MAINTENANCE-REPLACEMENT
Tools & Equipment
Part Description Source
Sealant PN ES49000-1 Keith
Polyolester Oil Viscosity ISO68-R134a Commonly Available
Mineral based 500 Viscosity-R12 Commonly Available

Expansion Valve Replacement
1)
 
Discharge system in accordance with Refrigerant Servicing instructions.
2)
 
Disconnect liquid line from inlet of expansion valve, and cap. Remove the thermal sense bulb from its clamp located on the suction tube of the evaporator and carefully remove insulation covering bulb.
3)
 
Disconnect the fitting that connects the valve to the coil and plug coil fitting.
4)
 
Install new expansion valve and o-ring (for o-ring fitting systems) in the reverse order.
5)
 
Lubricate o-ring with polyolester oil or apply sealant to fitting mating surfaces prior to assembly.
6)
 
Install the thermal sense bulb such that it makes contact with the suction tube along its entire length. When viewing the suction tube extending out of the evaporator, the sense bulb should be in the three or nine o’clock position (Figure A, figure b).
7)
  Attach the sense bulb using two zip ties. Insulate the bulb and expansion valve thoroughly with insulation (Figure C).


Figure A


Figure B


Figure C

 

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