Carrier TRANSICOLD Vector 8500, Operation & Service Manual

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00055 CHECK DEFROST AIR SWITCH
• ACTIVATION: The defrost air switch has called for a defrost cycle within 8 minutes of a defrost termina-
tion for 2 consecutive defrost cycles. (The air switch contacts were closed continuously for 15 seconds
before the defrost cycle was started.)
• UNIT CONTROL: Engine and Electric Operation: Alarm only. While this alarm is active, the defrost air
switch will NOT be used to initiate a defrost cycle; however the Defrost Timer will initiate a defrost cycle
90 minutes after the alarm comes on, and the manual defrost switch will remain operative.
• RESET CONDITION: Auto reset when defrost cycle terminates correctly, and the air switch does not call
for a defrost cycle within the 8 minutes following defrost termination, or alarm may be manually reset
using the display mounted keys or by turning the unit off, then back on again.
NOTE: Follow the steps below until a problem is found. Once a repair or correction has been made, the active
alarm should clear itself (refer to reset condition above). Operate the unit through the appropriate modes to see
if any active alarm occurs. Continue with the steps below as necessary.
CORRECTIVE ACTIONS:
1. Check Condition Of Refrigerated Compartment & Load
a. Check condition of refrigerated compartment doors & seals. Doors must be closed, and door seals
must seal and prevent entrance of outside air.
b. Check condition of evaporator. Check for blockage sufficient to cause an air pressure differential
across the coil great enough to close the contacts of the defrost air switch. Coil must be free of ice
following defrost.
c. Check condition of product. If product is warm and moist, frequent defrost cycles can be expected.
2. Check DAS Power And Wiring
a. Inspect switch, connector pins & terminals No physical damage to switch. No damaged or corro-
sion in connections.
b. If required, power switch by placing the unit in PC Mode. Check for power at switch connector.
Must have minimum 11 VDC. If not, check connectors and wiring between terminals for damage,
moisture or corrosion.
c. Check for continuity from switch connector plus terminal to 3MM-19. If good continuity is not pres-
ent, check connectors and wiring between terminals for damage, moisture or corrosion.
d. Check for continuity from switch connector minus terminal to 3MM-29. If good continuity is not
present, check connectors and wiring between terminals for damage, moisture or corrosion.
3. Check Defrost Air Switch and Tubing
Check tubing and perform testing as required. Refer to Section 8.8.11 .