Our troubleshooting situation begins with the customer’s description of the problem: “My air conditioner is blowing warm air.”

When you arrive, you confirm that the air handler on this 12-year-old, 4-ton split system is operating normally and the temperature in the building is far above the thermostat set-point. When you check the outdoor unit, you determine that this equipment is of a significant age, and based on your observation that the outdoor fan motor is operating and the compressor is off on overload, we’re showing the segment of the wiring diagram you focus on to begin your diagnosis in Figure 1.  (Note: You also find that the legend for this diagram is illegible due to the age of the equipment).

After disconnecting the power supply and allowing time for the compressor to cool, you perform electrical checks with a digital multi-meter and observe the following results:

     C to R: 2.5 Ω

     C to S: 3.1 Ω

     At CAP1 terminals: 60 µ

     At CAP2 terminals: 240 µ

     At relay terminals 2 & 5: 2,400 Ω

     At relay terminals 1 & 2: Infinity

Your two-part troubleshooting question:

  1. Which component definitely needs to be replaced in order to get this equipment operating?
  2. Which components would you consider replacing due to the age of the equipment and the lack of specific information about them?

Compare your answers with ours here.

Publication date: 6/24/2019

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