Furnace Short Cycling - Carrier Code 33

by Pat   Last Updated June 29, 2020 22:21 PM

We have a Carrier 58STA/STX Furnace that is only short cycling in Heat and not A/C. When it cuts off it is throwing Code 33 which is pointing to the following issues:

  • Dirty Filter or Restricted Duct System - Replaced Filters & Using a MERV 2, still trips
  • Loose Blower Wheel - Removed today and was not loose/excessive play
  • Defective Switch or Connections
  • Defective Blower Motor or Capacitor - Capacitor was at 50% of nominal, replaced and still occurs, have not done anything with blower motor.
  • Inadequate Combustion Air Supply (Flame Rollout Switch Open) - Flame Rollout Switch stays closed
  • Restricted Vent Sizing - Spec'd to House
  • Excessive Wind - Happens on Windy or Calm Days

If I either remove the filter or remove the blower access cover it does not throw the code.

Tags : heating furnace

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