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Defrost ineffective or too slow; drain refreezes

What is going on

Possible causes and checks for: defrost ineffective or too slow; drain refreezes.

Likely causes

  • Hot-gas solenoid not opening, compressor not running during defrost, fans not stopped, drain not heated, low-pressure-adjusting valve miscalibrated

Check in this order

  1. Solenoid coil and valve, timer contacts for compressor and fans, calibrate valve per mfr table, drain heat

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Source: General HVAC service practice — verify per model. Written in our own words; check the manual for your exact model.

For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.