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HVAC and Plumbing Distributor
Bubba Moore

Bubba Moore

Technical Services Manager
Southeast District

Compressor Problems & Troubleshooting

At Mingledorff’s we know compressors are the heart of the refrigeration system. It creates the pressure difference to move the refrigerant through the system. HVAC compressor checks are normally not done unless when troubleshooting the unit. Since compressors are expensive and their replacement can be time consuming, you need to be sure it is bad before replacing it. There are certain ways to identify compressor problems and measure the compressor windings and identify unmarked terminals.

One example would be a seized compressor. The compressor draws locked rotor amps and hums for several seconds. This can be caused by a mechanical or electrical problem within the compressor or by an external electrical problem. The unequaled refrigerant pressures can cause a compressor to pull lock rotor amps and appear to be seized. Also low incoming supply voltage to the compressor which can be caused from poor contacts on a contactor. The run or start capacitor to the compressor could be open or weak allowing the appearance of a seized up compressor. The scenarios above give the appearance of a seized compressor but are not and are repairable without replacing the compressor.  If the mechanical workings of the compressor fail or brake causing a sized up compressor the compressor will have to be replaced.

Another example would be low or no capacity. Compressors have valves, rings and plates that seal between the high – pressure and low – pressure sides of the system and the compressor. If either is damaged, correct operating pressures can never be developed. This condition can be checked two ways, one using pressure gauges and an amp meter. Using the pressure gauges, you would notice that the suction pressure is excessively high and the discharge pressure is excessively low, the HVAC compressor most likely has an internal problem that allows pressure to leak past the high and low sides of the compressor. Using the amp meter, you would notice a considerably lower than normal amp draws. The compressor would have to be replaced.

If you have ever had a single phase compressor that the terminals were not marked there is a fairly simple way to too identify which terminal is Common (C), Start (S), and Run (R). First follow all safety precautions, make sure power is off and if the compressor is in a pressurized system, do not place the meter probes directly on the compressor terminals. If the terminals are damaged and the system is pressurized, disturbing them to take readings could cause them to blow out, causing injury. Second remove the three compressor wires from all components. Then using your meter measure across the three compressor leads to find the two terminals that have the highest resistance reading. The remaining terminal is the Common (C) winding terminal. Next put one of your meter leads on common that was just found and the other lead on one of the other two remaining terminals to find the next highest resistance measurement. This is the Start (S) winding terminal. The last remaining terminal is the Run (R) winding terminal.

  1. Terminals C to R have the lowest resistance.
  2. Terminals C to S have the next highest resistance.
  3. Terminals R to S have the highest resistance.
  4. Resistance from C to S + Resistance from C to R = Resistance R to S.
  5. Example: C to S is (3.0) and C to R is (0.5) and R to S is (3.5)   (3.0 + 0.5) = 3.

HVAC Compressor

HVAC and Plumbing Distributor

HVAC compressor testing is needed to determine what is wrong and what may have caused the problem. There are some compressor symptoms that appear to be a compressor failure but are caused by another part on the system. Above is a brief example of compressor problems and how to check windings on a good compressor. There are a lot more system related problems that, if not corrected, can cause mechanical and electrical failure of a compressor.  

Sources: HVAC Servicing Procedures

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Alabama Locations

Anniston (256) 241-3026 105 E D St, Anniston, AL 36201
Auburn (334) 734-8011 2295 1st Ave, Opelika, AL 36801
Birmingham (205) 250-7714 516 31st St N, Birmingham, AL 35203
Dothan (334) 836-1035 205 Wedgewood Dr, Dothan, AL 36303
Gulf Shores (251) 968-2660 820 Commerce Dr, Gulf Shores, AL 36542
Huntsville (256) 859-2691 391 Nick Fitcheard Rd NW, Huntsville, AL 35806
Loxley (251) 964-2707 30020 Co Rd 49, Loxley, AL 36551
Mobile (251) 476-2220 5522 W Commerce Blvd West, Mobile, AL 36619
Montgomery (334) 262-4855 861 Plantation Way, Montgomery, AL 36117
Muscle Shoals (256) 383-6904 107 Commerce St, Muscle Shoals, AL 35661

Georgia Locations

Albany(229) 432-5254205 Baldwin Dr, Albany, GA 31707
Athens(706) 548-2563105 Whitetail Way, Bogart, GA 30622
Atlanta(404) 875-77551290 Tacoma Dr NW, Atlanta, GA 30318
Augusta(706) 651-19503618 Wrightsboro Rd, Augusta, GA 30909
Brunswick(912) 265-5193275 Rose Dr, Brunswick, GA 31520
Columbus(706) 322-38706201 W Hamilton Park Rd, Columbus, GA 31909
Conyers(770) 918-9132335 Gees Mill Business Pkwy NE, Conyers, GA 30013
Forest Park(404) 361-24745158-C Kennedy Rd, Forest Park, GA 30297
Gainesville(770) 297-93352472 Hilton Dr, Gainesville, GA 30501
Lawrenceville(678) 442-10602111 Cedars Rd SE, Lawrenceville, GA 30043
Lithia Springs(770) 948-3451320 Thornton Rd #106, Lithia Springs, GA 30122
Macon(478) 474-85445527 Thomaston Rd, Macon, GA 31220
Marietta(770) 426-05511060 Triad Ct, Marietta, GA 30062
Newnan(770) 239-210570 Enterprise Ct, Newnan, GA 30265
Peachtree Corners(770) 239-21006675 Jones Mill Ct, Peachtree Corners, GA 30092
Savannah(912) 232-1228103 Central Jct Blvd, Savannah, GA 31405
Statesboro(912) 764-8841126 W Parrish St, Statesboro, GA 30458
Valdosta(229) 245-8200363 Connell Rd, Valdosta, GA 31602
Warner Robins(478) 953-3727110 Byrd Way, Warner Robins, GA 31088

South Carolina Locations

Hilton Head(843) 689-34043715, 21 Hunter Rd, Hilton Head Island, SC 29926

Florida Locations

Fort Walton Beach(850) 244-201776 Beal Pkwy SW, Fort Walton Beach, FL 32548
Panama City(850) 913-05853012 Lisenby Ave, Panama City, FL 32405
Pensacola(850) 438-10054405 N. Palafox Street, Pensacola FL 32505

Mississippi Locations

Hattiesburg(601) 579-96701851 Lincoln Rd, Hattiesburg, MS 39402
Ocean Springs(228) 497-5090Sunplex Industrial Park, 5717 Suntec Drive, Ocean Springs, MS 39564

Commercial Sales

Norcross – North Georgia Hub
(800) 282-4911

Birmingham – North Alabama Hub
(205) 250-7714

Macon – Southwest Hub
(800) 342-9250

Loxley – Gulf Coast Hub
(800) 239-7419

Savannah – Southeast Hub
(800) 822-7617

Commercial Parts

 CompanyWeb AddressDescription
Airzonewww.airzoneinc.comCustom and Underfloor Air Handlers
Aladdin Metal Productswww.aladdinmetalproducts.comCurb Adapters and Roof Curbs
Aprilairewww.aprilaire.comIndoor Air Quality Products
Autaniwww.autani.comBuilding Automation and Controls
Bardwww.bardhvac.comHeat Pumps,Gas/Electric, and Wall Mounted Air Conditioners
Bryantwww.bryant.comCommercial, Industrial, Residential Heating & A/C Products and Controls
Carrierwww.commercial.carrier.comCommercial and Residential Heating & A/C Products
Data Airewww.dataaire.comPrecision Air Control for Data Processing Centers
 DXairwww.dxair.comPool dehumidification systems
 First Companywww.firstco.comFan Coil Units
Global Plasma Solutionswww.gpshvac.comAir Purification and Bi-Polar Ionization
 Greewww.greeusa.comPTACs
 Hayes Fluid Controlswww.haysfluidcontrols.comHose Kits and Control Valves
 iAirewww.myiaire.comCommercial Air Purification using ionization with energy savings
 IslandAirewww.islandaire.comPTACs, Vertical Units, Water Source Heat Pumps
 i-Vuwww.commercial.carrier.comBuilding Automation and Controls
 Magic Airewww.magicaire.comFan Coil Units
 Micro Metlwww.micrometl.comRoof Curbs, RTU Accessories, & ERVs
 Modinewww.modine.comGas-Fired Unit Heaters, Duct, Furnaces, Hot Water Cabinet Unit Heaters, Makeup Air, and Dedicated Outdoor Air Systems
 Network Thermostatwww.networkthermostat.comInternet Thermostats, Wifi Themostats, Ethernet Thermostats
Paynewww.payne.comResidential Heating & A/C Products
Rawal Deviceswww.rawal.comContinuous Capacity Modulation and Dehumidification for DX Systems
Renew Airewww.renewaire.comFixed-Plate ERVs
Totalinewww.totaline.comCompressors, Parts, and Supplies
United CoolAirwww.unitedcoolair.comModular All-Indoor HVAC Systems
 Warren Technologywww.warrenhvac.comElectric Heaters
 Wilo Pumpswww.wilo-usa.comPump Systems for HVAC and Water Supply and Sewage