Haier HC18D2VAR Service Manual page 26

will reveal this problem. With sealed relays, use an ohmmeter to test for open or closed contacts.
ELECTRICAL CHECKS
1. BE SURE ALL THE ELECTRICAL POWER IS OFF TO THE COMPONENT BEING
CHECKED.
2. Remove at least one wire from the component being checked.
3. Measure the resistance of the holding coil with an ohmmeter
A. A specific resistance indicates a good holding coil.
B. Infinite (∞) resistance indicates a relay with an open holding coil. REPLACE the defective
relay with an appropriate service part.
4. Measure the resistance across the normally closed (NC) relay contacts.
A. The resistance should be zero (0) ohms.
B. If the resistance is more than 0.2 ohms the contacts are pitted. REPLACE this relay with
an appropriate service part.
5. Measure the resistance across the normally open (NO) relay contacts.
A. The resistance should be Infinite (∞)
B. If the resistance isn't Infinite (∞),.REPLACE this relay with an appropriate service part.
MECHANICAL CHECKS
In relays ,mechanical faults are few. But check relay body for signs of physical damage .
AIR FLOW
Indoor coil air flow in any air conditioning system is critical. Too much air and the system will not be able
to suffers lack of dehumidify in cooling. insufficient air flow while cooling may result in coil freeze up,
excessive dehumifification and lost capacity.
Checking air flow is the most important diagonistics a service technican can perform. Instructions are
rrovided to show how to measure pressure drop across the coil. If pressure drop tables are available,
they indicate the cubic feet of air per minute(CFM) moving through the coil. An inclined manometer or
magnehilic guage can be used for measurement.
A velometer measures the velocity of the air in feet per minute(FPM). If the area of duct is known,
the velometer reading times the area of duct (in square feet ) calculates the air flow.
If the indoor unit has an electrical heater, air flow can be estimated by measuring the air temperature
entering and leaving the heater and calculating the CFM.
COMPRESSOR AND SYSTEM FAULT DIAGNOSIS
Compressor manufacturers state that maul of the compressors returned as defective have been
misdiagnosed.To ensure that does no t happen, the technician must determine if the compressor has
failed or if another control has either failed or stopped the compressor from operating after detecting a
problem. The following procedures should help determine if the compressor has failed.
Prior to replacing a suspected failed compresso ，a thorough check must be made of all existing electrical
electrical components .If not done ,a replacement compressor might also failed or not operate at all
WARNING: THE FOLLOWING PROCEDURES SHOULD ONLY BE ATTEMPTED BY QUALIFIED SERVICE TECHICIANS
EQUIPPED WITH PROPER TOOLS, SAFTY PROCEDURES AND EQUIPMENT AND INSTRUMENTS TO PERFORM
THE DESCRIBED REPAIRS.
26
Central Air Conditioning
▼
CFM (Electrical Heater) =VOLTS×AMPS×3.414
Model: Condensing Unit, HC13-D2
Fig. 9-5
1.08 ×TEMP RISE