So you pull the relay cover off the compressor, remove the relay/overload and this is what you see. In almost every instance when the clutch fails, it becomes burnt and discolored. There are three sets of windings arranged around the stator, and the ends of these windings terminate on a three‐pin connector that provides for the electrical connection through the compressor shell. Insulation resistance is usually measured between motor windings and earth using an insulation tester or megometer. contaminants on the windings or not. The megger will help to detect areas of deteriorating insulation where the windings may soon short. To check the integrity of the compressor’s windings, complete these steps. A motor fails when its windings short to ground, short to each other, or open--a break in the winding's wire. This slams 500v or 1000v through the windings. A shorted motor will read 0 ohms across windings, to ground, or both. Use your multimeter in continuity setting, measuring the Ohms across 3 compressor terminals, Common to Run should have the lowest resistance, Run to Start should have the largest resistance, In all single-phase instances the value from Run to Start should equal the sum of the values from Common to Run and Common to Start, On a 3-phase compressor the resistance values should be within 3% of each other across each of the terminals. Usually you check mega-ohms by reading the resistance between compressor shell and the windings. • Mechanical failure of the IPR, valves, scroll or a bearing problem • Electrical failure of the windings in the compressor Before condemning a compressor for not starting these items must be confirmed. These problems are resolved by checking the voltage going to the compressor, the electrical components, wiring to the components, and the resistance of the compressor motor windings.” Chapter 3. … – For the good winding,the ohm value must infinity.It mean … If you find that an AC compressor is getting the proper voltages, has a good capacitor, and will not run or is tripping the circuit breaker, it could be that the motor windings are the problem. Checking the coils of a motor in permanent Star connection. Can anybody tell me how to ring test a 230 volt a/c compressor. The output voltage of the compressor depends on the amount of magnet winding strength. It is not necessary to wire the harness up to the Common, Start and Run terminals exactly because the compressor will start regardless. How To Test or Check Air Conditioner Compressor Motor Windings. Hermetic motor environment and consequences Applying IRT to hermetic compressors is a two step procedure, due to the nature of the operating environment of the compressor motor. The most common type though is the -so called- squirrel cage rotor. Touch one lead of the meter to the copper pipe going into the compressor (discharge or suction). If the winding's insulation wears away near the motor's case, the bare-wire winding shorts to ground. Now if you want to check the Air conditioner compressor then its also too simple, in air conditioner compressor we have label in which the R , S and C written or parked. Happens every 18 months to two years (depending on type of aircraft) and takes three weeks. Our default site experience provides general information and content for every region served. Capital omega is the symbol for the resistance unit ohm. To properly test the motor windings you must use a Mega meter. In this HVAC training video program, Jim shows how to eliminate the mystery behind compressor motor windings and learn how to use a meter to make electrical checks on compressors. Most repair shops will use a "megger" or a ground insulation tester. Grounded Winding – Grounded windings are nearly the same as an open winding except the winding is touching the casing of the compressor. PAGE 1 of 2 - How to check the Windings of a 3-Phase AC motor. Examine the A/C clutch with a flashlight. showing how to check for continuity. Many simple "across the line" single-phase and 3-phase motors (used in household appliances and industry respectively) can be checked simply by changing the range of the ohm meter to the lowest offered (R X 1), zeroing the meter again, and measuring the resistance between the leads of the motor. The same thing is happening with some of our B737s. Put leds of multimeter and test the A and B terminal, then check the A and C terminals and then B and C. Unlike a megger, a multimeter doesn't have enough volts to find shorts on mains equipment. Let’s say you’re gonna do some tests on your refrigerator compressor to see if it’s okay. A start winding and a run winding. If one winding is open…… two of the readings will be infinite………….. Compressor burnout is a very specific mode of failure that may be caused by high temperatures in the motor windings or discharge area of the compressor. At this point you will see the terminations of the windings where they enter the compressor. A slipping AC compressor clutch is a sign of severe wear, shorted clutch coil or an incorrect air gap (explained later). 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To determine whether a 3 phase motor is still good or has gone bad, a simple ohmmeter test across the windings of the motor will reveal its true state of health. Then set multimeter on Ohm. Check the Compressor Windings for an Open Winding. The wire in the windings use an insulating covering as an isolation barrier. So you pull the relay cover off the compressor, remove the relay/overload and this is what you see. If a compressor has been malfunctioning or causing internal thermal overload, it can damage the insulation surrounding the windings. Would I be a bad person if I didn't tell my neighbors to be more careful with gas on his property. No Locate leak, repair and recharge Yes Check amp draw, compare to data in Checking the Compressor Windings. I use to know many years ago, but just can’t remember what is suppose to = what, when using the ohm meter, and how to tell if there is a short to ground. Includes information on single-phase and three-phase compressors. The windings (all three in a three-phase motor) should read low but not zero ohms. These magnets are used to generate enough electricity for the unit. If your compressor is properly getting the voltages and is comprised of a good capacitor yet not working well, then there must be something wrong with the windings (electrical failure). Then set multimeter on Ohm. Move the refrigerator away from the wall and unplug its power cord from the wall receptacle. The D Check. To check compressor windings, first shut off the power to the unit. Check for burnt, damage to body or cooling fan or shaft. An A/C compressor clutch coil is a simple device made of fine windings of wire wrapped into a coil. If the compressor passes the above tests, take a multimeter set to R x 10,000 (10K) and check each winding to ground. Let's first see the leads of the motor in permanent Star connection: The rotor is built around the shaft that connects directly to the compressor crankshaft. Connect your negative, or black battery cable with the grounded contact in the compressor. If it is … This is easier to explain by a diagram than it is to write ….but if you have done it before it will come back to you. First of all gave name to the terminals, for example you gave name to terminals A,B,C. Verify all the terminals. You need to figure out which posts correspond to the Start, Main, and Run windings ‘cuz if’n you don’t and you go and wire that relay/overload up wrong, well, you just went from a $30 easy-as-pie repair to a $300 rectal cramp. {It is not necessary to check the other pins}. Next, go to the compressor electrical connection box on the compressor and open the cover.