WD Catalog 2018

10-5

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HVAC Control System Variations

CAUTION

Do not operate AC system with incorrect refrigerant

charge or compressor damage may occur.

Compressor Cycles, but AC System Does Not Cool.

All electrical components in the clutch circuit appear to be function-

ing properly. Refer to

Chapter 8

for troubleshooting procedures.

Power to Trinary™ OK and Compressor Still Runs

Continuously.

The high side cutout switch may not be functioning, so one of the

problems described below is causing the abnormal pressures.

Check high side pressure. If it approaches 300 PSIG, a

serious problem is indicated.

a. The AC system may be overcharged.

b. There may not be enough air flow through the condenser

or it may be blocked by debris.

c. The condenser may be too small for operating conditions.

d. There may be a restriction inside the system (bent or

kinked lines or hoses, sludge or moisture in system, etc.).

e. The thermostat may not be functioning.

Fan Clutch or Shutter Override Circuit.

Note:

In normal operation, Trinary™ switch terminals #3

and #4 are normally open. (Normally closed Trinary™

switches are used with some air-clutching engine

fans.) As the system pressure reaches mid-range

(200-230 PSIG), the switch closes and supplies power

to the fan clutch or shutter control circuits.

Fan Clutch or Shutter Cycles Too Often or Stays On Too Long:

Connect gauge set to AC system:

a. Watch high pressure side increase until mid-range pres-

sure is reached.

b. If fan engages or shutter opens at the proper pressure,

the Trinary™ is OK.

c. The problem is the condenser—check for debris or lack of

air flow through the condenser fins. The condenser may

be too small for conditions.

Fan or shutter cycles at less than 180 PSIG or remains on

below 150 PSIG:

a. The Trinary™ is functioning below it’s proper operating

range and must be replaced.