To test for a short to ground, set a multimeter to the ohms scale and touch one lead to a clutch coil terminal and the other to a ground point on the compressor. - Testing windings for ground with an ohmmeter. So now you are sure the motor windings have ground fault. One of the tips should touch the motor's case while the other touches one of the exposed wire leads. Remove the power feed (i.e. A VOM connected to the compressor circuit indicates that no current is being drawn, but the condenser fan is running properly. could also be condenser fan … Unfortunately, in real life this is not always possible for … A ground fault is a type of fault in which the unintentional pathway of the straying electrical current flows directly to the earth (to the ground). Two methods can be used to identify and isolate a ground fault; these are the circuit continuity check and the voltage drop check. B10A9 - Control Circuit for A/C Compressor B10A911 - Control Circuit A/C Compressor: Short to Ground Possible Symptoms. Compressor performance parameters follow basic dimensional analysis and similarity rules which allow to design and test stages at some reference conditions and then apply them at actual (dimensional) conditions. This is important because the pins on the compressor connector are small, so select connectors that will fit in the compressor plug and not short out by touching each other. Scrape off paint and clean a spot on the motor-compressor shell for testing. Then, I further verify that by taking the plug off the compressor and test the lugs to ground or on a clean piece of copper pipe, such as the suction line. With a Test Lamp. (b) Earth Continuity and Resistance Test (c) Power Supply Test (d) AC Motor Winding Continuity Test (e) AC Motor Winding Resistance Test (f) Insulation Resistance Test (g) Running Amps Test General Inspections For the three-phase motor, do the following: (1) Check the appearance of the motor. Put 1 test lead on one terminal and the other on the bare metal. A few of the general test procedure topics covered include current relay and potential relay checks, valve plate checks, and mechanical scroll checks. Test the lead. Check for power AND ground to the compressor. If the DMM does NOT display infinite resistance (OL), there is a short to ground in the circuit. SHORT TO GROUND With the wires removed, take an ohmmeter and set it on the R X 1000 scale. You should see no conductance. Install jumper connectors onto the compressor electromagnet. There should be wires running from the top or side of the compressor. Connect ground lead to compressor ground location using provided alligator clip attachment. The insulation of the windings can become compromised by excess heat, vibration, or contaminants and cause the windings to make contact with one another (shorted) or with the compressor shell (shorted to ground). Going through these simple steps may save you time, money, and hassle, and help you decide whether it is worth it to repair your compressor, or if it would be better to replace it. If your read a low resistance, such as 0, or your meter beeps, then the compressor is shorted to ground and needs to be replaced. If you find a short, replace the clutch coil. If you need to replace a GFCI outlet, … Here, too, the circuit is "short," in that it has bypassed the circuit wiring, so a ground fault can technically be defined as one type of short … A question regarding a AC clutch circuit that remains engaged due to a short to ground. Climate Control not working (Not cooling) Possible Causes. On the simplest meters, you use the resistance setting; sophisticated models have a continuity setting that flashes a light or beeps a tone to let you know a connection is a short circuit. A check for short circuits is one of the most basic tests you can perform with a multimeter. Take one probe from the meter and find a good ground. So you do another mega test & this time find less than 1 meg ohm. It is a fairly simple task to confirm the integrity of all ECU ground circuits in fairly short order. If the braker trips right away when reset, its a dead short. Switch meter to insulation test position and select 500 VDC test voltage. if you get any reading it is grounded.(shorted). We are looking for the terminal that goes to the a/c compressor clutch. You will need a test light or power probe for this part of the testing. Better yet, if you are going to be HVAC technician then get yourself a megaohm-meter. A catastrophic motor fail-ure within a (semi-) hermetic compressor that contains oil and refrigerant at best involves extensive clean up procedure, and at worst If you have any reading asides this, then you have a ground fault. for a short to ground. And what will cause a compressors windings to short to ground? The compressor motor has burned out, is internally shorted or gounded. Once a short to ground is detected, a cata-strophic failure of the device has occurred and it is too late for preventive maintenance or proactive remedies. Compressor windings can also become shorted by … A service technician will use a VOM and typically will find low resistance (low Ohms) between one or more compressor terminals and ground. To perform an ohmmeter continuity test, proceed as follows: Disconnect the power and remove the wires from the motor terminals. If the compressor is a 3phase type it will have 3 equal resistances between c r s. grounded will be checked in same way.3 internal overloads.1 of three could open when hot. The wire in the windings use an insulating covering as an isolation barrier. Checking for an Open Winding- To check for open winding in the compressor, you will use the Ohmmeter and attach 1 probe to T1 and the other probe to T2. You should NOT see continuity during this test. Connect the other lead of the meter to a good ground. Disconnect the load and connect one lead of the test lamp to battery positive voltage. 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. Fuse(s) faulty; Wiring and/or Connector(s) from/to Compressor Regulating Valve (N280) faulty Multi meter shows all 3 windings open circuit so no ground fault. Three-phase test procedure topics covered include checking for an open motor winding/internal overload and checking motor windings for short to ground. A motor fails when its windings short to ground, short to each other, or open--a break in the winding's wire. You reset power supply & run compressor. This step will require a volt-ohm tester. This is most of the time located on the side or top of the compressor and is typically 2, sometimes 3, wire harness. Pulled compressor plug off and ohmed all 3 to ground, they all 3 had infinite resistance and to corrosion at all. The AC clutch relay completes the circuit to the compressor clutch. Make certain that all system leaks are found and repaired and that the system is properly evacuated before putting the new compressor into service. This should reveal the contacts that you’ll use to test the compressor. After a few seconds it trips the power supply again. If you do, the clutch coil has shorted to ground. Common heat pump compressor problems can often be diagnosed by the homeowner, without the need to call a costly service repair technician. Every time the short occurs, the compressor torque drops sharply, the compressor may shudder a bit visibly as a result, and this shudder shakes the winding enough to separate the short. Switch meter to insulation test position and select 500 V DC test voltage. find clean copper and check with 1 probe on copper and other on terminals. Two types of shorts can occur in a compressor motor, a turn-to-turn short within a winding or a winding-to-frame short. Was this related to the cap blowing a month ago? Mega meter shows 1 meg ohm. If the winding's insulation wears away near the motor's case, the bare-wire winding shorts to ground. I replaced the cap, found several loose wire connections which I tightened, and cleaned the condenser. After that connect the multimeter negative to ground, it should read zero volts, also connect the positive to the ground; it should also read zero volts. fuse, control module) from the suspect circuit. Depress test button on test probe (or on meter) for test duration period (60 seconds). Touch test probe to shunted compressor terminals. So you suspect possible ground fault. Switch the lead to the other terminal and repeat. 00898 - Control Circuit A/C Compressor: Short to Ground Possible Symptoms. most likely a compressor shorted to ground if 3 phase. Climate Control not working (Not cooling) Possible Causes. The compressor will need to be replaced if it is determined that the dead short is actually caused by the compressor. Continue Reading High temperatures break down the motor winding insulation, which may cause a loss of electrical resistance and result in a short to the ground or even an open winding. Connect ground lead to compressor ground location using provided alligator clip attachment. check all to ground. Check for burnt, damage to body or cooling fan or shaft. Figure 14-33. Left the compressor unplugged and turned on ac and the condenser fan motor came on and stayed running. Ohmmeter Continuity Test (Low-Resistance) Procedure . You will need to find the signal wire connector that attaches to the compressor clutch. I was back today and found the windings shorted to ground. Take the other probe and touch it to EACH terminal in the compressor. A compressor must be replaced with a short to ground. To check for short to ground, connect one terminal lead to one clutch coil terminal and the other lead to a metal contact point on the compressor. I was on a call about a month ago, and found a blown dual capacitor. Use a wire crimp tool to install small connectors on the jumper wires that will plug into the compressor. The Refrigerant Compressor may need to be replaced if the Compressor Regulating Valve (N280) is not available separately. Simply replacing a compressor that has a short-to-ground may not alleviate the actual cause for compressor failure; namely the presence of moisture or acid in the system. Touch test probe to shunted compressor terminals. Sometimes a ground fault is due to one fastener being left loose after a service procedure has been performed. Then switch to the other clutch coil terminal and check for short to ground. Press on the sides of the plastic fittings and pull on the wires to remove them. If it were 100% rigorously followed, this process would guarantee a perfect matching of the performance. While the short is in place, the current through the shorted winding shoots up and a lot of heat is produced. The white wire is your live wire that carries electric current, while the black wire is your ground wire. (You may need to scratch the paint on the compressor or scrape the copper tubing at the compressor to assure a good connection). A AC clutch short to ground relay that is stuck in the closed position will leave the compressor engaged at all times. If the compressor is in fact shorted, or what we call a short to ground, it can do several things, but most likely trip the breaker first. Depress test button on test probe (or on meter) for test duration period (60 seconds). If the Ohmmeter reads 0.L or infinity then there is an open winding. Your tester will have two wires with lead tips. compressor start parts or shorted compressor- single phase. If we have ground there we 100% know that wire is shorted to ground. Between the 3 terminals at the compressor I measured 1.4, 2.9, and 3.2(s-r). Read the results on the tester, then repeat the … I want you to disconnect the compressor clutch wire and test the dark green wire terminal at the fuse box for ground. 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