{"id":43969,"date":"2023-07-21T17:50:32","date_gmt":"2023-07-21T21:50:32","guid":{"rendered":"https:\/\/cematraining.com\/?page_id=43969"},"modified":"2026-03-23T16:13:15","modified_gmt":"2026-03-23T20:13:15","slug":"how-to-check-a-capacitor-while-the-system-is-running","status":"publish","type":"page","link":"https:\/\/cetechsupport.com\/es\/how-to-check-a-capacitor-while-the-system-is-running\/","title":{"rendered":"How to check a capacitor while the system is running."},"content":{"rendered":"\n

Yes with a multimeter and using the microfarad function to check a capacitor maybe nice. But this does not test the capacitor under “load” conditions.<\/strong><\/p>\n\n\n\n

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Let’s take a look at a typical high voltage circuit of a residential air conditioner or heat pump outdoor unit.<\/strong><\/p>\n\n\n\n

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Now to do this we will need to get a few measurements.<\/strong><\/p>\n\n\n\n

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Turn the system on and let the system run for 5-10 mins to stabilize operation.<\/strong><\/p>\n<\/div>\n\n\n\n

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Lets start collecting amp draws and voltages.<\/strong><\/h4>\n\n\n\n
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1st get the amp draw of the fan motor on the brown wire connected to the fan terminal of the capacitor. Example 0.5 Amp<\/strong><\/p>\n\n\n\n

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2nd<\/strong> get the amp draw of the compressor start wire, the blue wire connected to the herm terminal of the capacitor. Example 4.4 Amps<\/strong><\/p>\n\n\n\n

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3rd<\/strong> Now lets get the voltage of the condenser fan motor between the brown wire and yellow common wire at the capacitor. Example 271 Volts<\/strong><\/p>\n\n\n\n

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4th<\/strong> lets get the voltage of the compressor between the blue start wire and yellow common wire at the capacitor. Example 297 Volts<\/strong><\/p>\n\n\n\n

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Now we can do some math. Here is the formula we will use.<\/strong> Use this formula for each component.<\/strong><\/p>\n\n\n\n

Some formulas use 2650, 2652, 2654. We will use 2652.<\/strong><\/p>\n\n\n\n

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Lets do the fan first, 2652 X 0.5 amps \/ 271 volts = 4.9 mfd <\/strong><\/p>\n\n\n\n

Next the compressor, 2652 X 4.4 amps \/ 297 volts = 39.3 mfd <\/strong><\/p>\n\n\n\n

If your capacitor is rated for 40\/5 mfd, the readings are within 10% and the capacitor is good.<\/strong> <\/p>\n\n\n\n

Another Example; if the capacitor is rated 45\/5 mfd, an allowable tolerance range for our example is 49.5 mfd – 40.5 mfd. <\/strong><\/p>\n\n\n\n

Compressor 2652 X 6.1 amps \/ 297 volts = 54.5 mfd. This capacitor is performing at 54.5 mfd, which is greater then the 10% tolerance. This capacitor should be replaced.<\/strong><\/p>\n\n\n