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=1W08vFdhtLkAnd:https://m.youtube.com/watch?v=raG_N_hz6ng

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.

I can count on one hand the number of failed compressors I’ve run in to in 30 years of servicing them.

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

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.

Troubleshooting Compressor Windings | Good Sam Community

Ozlander
Explorer
Mar 30, 2019
Maybe he's using the new hi-voltage 9 volt batteries.
3_tons
Explorer III
Mar 30, 2019
“ACID
Just keep touching your leads on the terminals of compressors with grounded windings,
It will happen. I don't have much HVAC experience, just a little shy of 40 years .”

Ok, so it sounds like this occurs when the ohm meter leads make contact with two of the three compressor terminals (then goes BOOM), and with a non-flammable refrigerant correct??...Help us understand what electrical process is it that makes this occurrence happen - dummy me here, I don’t get it...

Thanks
sayoung
Explorer
Mar 30, 2019
RLS7201 wrote:
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

ACID
Just keep touching your leads on the terminals of compressors with grounded windings,
It will happen. I don't have much HVAC experience, just a little shy of 40 years .
S_Davis
Explorer
Mar 29, 2019
3 tons wrote:
In some cases folks fall victim to a simple R&R business model, very prevalent with auto diagnostics where troubleshooting requires lots of specialized training, time and moola...However, R&R may often be the first best option.

I see my job as a business owner and HVAC tech to diagnose the problem and then educate the customer on their options and let them decide what is the best solution for them. An educated customer is a good customer, it does not take that much time and after all they are the boss.
3_tons
Explorer III
Mar 29, 2019
In some cases folks fall victim to a simple R&R business model, very prevalent with auto diagnostics where troubleshooting requires lots of specialized training, time and moola...However, R&R may often be the first best option.
C_Schomer
Explorer
Mar 29, 2019
Yes, kudos to the good troubleshooters! I agree, very few truly bad compressors. I’ve saved a lot of sick Units by replacing the drier, doing a really good evacuation using a micron gauge and recharging. It’s too bad the EPA made simple jobs like that so time consuming and complicated and now it’s so often, cost prohibitive. The young pups aren’t learning solid troubleshooting skills anymore and the old-timer/mentors, are retiring. Craig
S_Davis
Explorer
Mar 29, 2019

I think it may have less to do with ethics and more to do with mis-diagnosis from a general lack of training speciality. In this scenario R&R is often the expedient fix.

I would agree after 30 years in the HVAC trade it seems like more and more there are a lot of part changers with very little diagnostic ability.
3_tons
Explorer III
Mar 28, 2019
Sorry, double post...
3_tons
Explorer III
Mar 28, 2019
hypoxia wrote:
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.

Chris, you are a great technician with great ethics. Many are not.

I'm always amused by the number of posts indicating bad compressors. Folks seem to want to find a reason to buy a new unit. I will go to great lengths to keep an R134A unit alive and avoit the R410 units.

The major compressor manufacturers say a large majority of compressors returned under warranty are good and the technician was wrong in their evaluation.

I think it may have less to do with ethics and more to do with mis-diagnosis from a general lack of training speciality. In this scenario R&R is often the expedient fix.
hypoxia
Explorer
Mar 28, 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.

Chris, you are a great technician with great ethics. Many are not.

I'm always amused by the number of posts indicating bad compressors. Folks seem to want to find a reason to buy a new unit. I will go to great lengths to keep an R134A unit alive and avoit the R410 units.

The major compressor manufacturers say a large majority of compressors returned under warranty are good and the technician was wrong in their evaluation.