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DanielC, HVAC Technician
Category: HVAC
Satisfied Customers: 96
Experience:  11 years experience in repair and replacement of residential and light commercial HVAC. CFC Certified
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What is the proper way to check a run capacitor with a digital

Resolved Question:

What is the proper way to check a run capacitor with a digital multimeter? and what is the procedure for checking a dual run capacitor? how does it differ
Submitted: 7 years ago.
Category: HVAC
Expert:  DanielC replied 7 years ago.

The meter must read microfarads (also called "capacitance")


Single capacitor.


Remove the wire/s from one side of the cap. Place one test lead on each terminal. After a few seconds the reading should display.


For instance, a 40 mfd cap, with a 105 variable, should read 36.0 to 44.0 If it is out of that range, the capacitor is technically bad. Will it continue to work? probably, for a while at least, but it will be potentially causing premature failure of the component it is supporting.


For a Dual cap.


Remove the wires from the "herm" (compressor) and "fan" side of the cap. Place one test lead on the common terminal, and one on the "herm" terminal to read that "side" of the cap, and then place that lead on the fan terminal to read that "side" of the cap.


The variable percentage is different for various capacitors, always check each one individually. If the markings are worn off, never assume the variable to be more than 10%.

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