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3_tons's avatar
3_tons
Explorer III
Mar 27, 2019

Troubleshooting Compressor Windings

For those with the appropriate skill level, I found these two items of interest to help evaluate leaky or failed insulation on air conditioner compressor motor windings. Readings are taken across the three terminals which are, C=Common, S=Start, and R=Run. Before removing outside weather cover, first make certain that power is disconnected (and verify), then in the interest of meter accuracy, disconnect the wire leads from each terminal before taking readings.

Note that one of the three wires (Common) may connect to a round thermistor device (for over temp protection) which can fail and can be removed (lifts out) and replaced if necessary.

https://m.youtube.com/watch?v=1W08vFdhtLk

And:

https://m.youtube.com/watch?v=raG_N_hz6ng
  • 3_tons's avatar
    3_tons
    Explorer III
    Mar 28, 2019
    S Davis wrote:
    Sounds like someone discharged a capacitor the wrong way.


    Sounds more like it...
  • RLS7201's avatar
    RLS7201
    Explorer II
    Mar 27, 2019
    Wild Bill 888 wrote:
    Take the readings from the wire leads & not the compressor terminals, the current from the meter can under certain conditions, example grounded, blow the terminals off the compressor shooting out very acidic oil & refrigerant .


    How does a meter with a AA or 9v battery blow the terminals off? Is there a new hydrogen/oxygen refrigerant ?

    Taking measurements off the leads may cause you to replace a good compressor due to a bad lead or bad connection.


    And while your questioning his electrical expertise, I'll question his refrigerant/oil expertise. It's not acidic.

    Richard
  • Wild_Bill_888's avatar
    Wild_Bill_888
    Explorer
    Mar 27, 2019
    Take the readings from the wire leads & not the compressor terminals, the current from the meter can under certain conditions, example grounded, blow the terminals off the compressor shooting out very acidic oil & refrigerant .


    How does a meter with a AA or 9v battery blow the terminals off? Is there a new hydrogen/oxygen refrigerant ?

    Taking measurements off the leads may cause you to replace a good compressor due to a bad lead or bad connection.
  • 3_tons's avatar
    3_tons
    Explorer III
    Mar 27, 2019
    Chris Bryant wrote:
    I can count on one hand the number of failed compressors I’ve run in to in 30 years of servicing them.


    I dare not doubt that - yet if the meter findings are significantly askew, it might indicate the presence of a leaky winding (or even a pending failure) which could explain why *running amps (via clamp-on meter) exceed mfg’s published running amps...This would naturally assume that the **caps (or in some cases, the soft-start device) are in good shape. Just saying...

    *Note that running amps involve compressor and fan.
    **Warning: the caps contain very high voltage and should only be serviced by a qualified technician...

    3 tons
  • Chris_Bryant's avatar
    Chris_Bryant
    Explorer II
    Mar 27, 2019
    I can count on one hand the number of failed compressors I’ve run in to in 30 years of servicing them.
  • sayoung's avatar
    sayoung
    Explorer
    Mar 27, 2019
    Safety lesson for you amature AC techs. Take the readings from the wire leads & not the compressor terminals, the current from the meter can under certain conditions, example grounded, blow the terminals off the compressor shooting out very acidic oil & refrigerant . Learned that the exciting way very early in my career.

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