Air conditioner compressors usually fail due to one of two conditions: time as well as hours of operation (wear out or abuse. There are several failures that can occur elsewhere within the system that will result in a compressor failure, however these are more uncommon unless the system has been substantially abused.
Usually abuse is a result of extended running with improper freon charge, or as a consequence of improper service in the process. This improper service can include overcharging, undercharging, installing a bad starter capacitor as a replacement, removing (as opposed to repairing/replacing) the thermal limiter, insufficient oil, mixing incompatible oil types, or wrong oil, installing the compressor over a system that had an important burnout without taking proper steps to remove the acid through the system, installing a bad compressor (too small) for that system, or installing A/C Compressor on the system which had some other failure which was never diagnosed.
The compressor can fail in only a few various ways. It may fail open, fail shorted, experience a bearing failure, or even a piston failure (throw a rod), or experience a valve failure. That is pretty much the complete list.
Each time a compressor fails open, a wire within the compressor breaks. This really is unserviceable and the symptom is that the compressor fails to run, although it may hum. In the event the compressor fails open, and after the steps here will not fix it, then this system may be a good candidate for a new compressor. This failure causes no further failures and won’t damage the remainder of the system; if the remainder of the system is not decrepit then it would be affordable to merely put a whole new compressor in.
Testing for any failed open compressor is easy. Pop the electrical cover for the compressor off, and take off the wires as well as the thermal limiter. Employing an ohmmeter, look at the impedance in one terminal to another across all three terminals of the compressor. Also appraise the impedance for the case from the compressor for those three terminals.
You need to read low impedance values for all terminal to terminal connections (several hundred ohms or less) and you ought to have a superior impedance (several kilo-ohms or greater) for those terminals towards the case (which can be ground). If any of the terminal to terminal connections is definitely a high impedance, you have a failed open compressor. In unusual cases, a failed open compressor may show a low impedance to ground from one terminal (which is one of many terminals related to the failed open). In this instance, the broken wire has moved and is contacting the situation. This condition – which is quite rare but not impossible – might cause a breaker to trip and could result in a misdiagnosis of failed short. Be careful here; do an acid test in the valuables in the lines before deciding how to proceed with repair.
When a compressor fails short, what will happen is the fact insulation on the wires has worn off or burned off or broken inside the shower faucet. This enables a wire on a motor winding to touch something it ought to not touch – most often itself a turn or two further along on the motor winding. This results in a “shorted winding” that can stop the compressor immediately and cause it to heat and burn internally.
Bad bearings may cause a failed short. Either the rotor wobbles enough to make contact with the stator, leading to insulation damage that shorts the rotor either to ground or even to the stator, or end bearing wear can allow the stator to shift over time until it begins to rub from the stator ends or even the housing.
Usually when one of these brilliant shorts occur, it is really not immediately a tough short – which means that initially the contact is intermittent and comes and goes. Each time the short occurs, the compressor torque drops sharply, the compressor may shudder a bit visibly because of this, and also this shudder shakes the winding enough to separate the short. Whilst the short is at place, the existing through the shorted winding shoots up and lots of heat is produced. Also, normally the short will blow some sparks – which produces acid inside vqxigq air conditioning unit system by decomposing the freon into a mixture of hydrochloric and hydrofluoric acid.
As time passes (possibly a couple of weeks, usually less) the shuddering and also the sparking as well as the heat as well as the acid cause insulation to fail rapidly on the winding. Ultimately, the winding loses enough insulation the inside of the compressor is literally burning. This may only carry on for a few minutes nevertheless in that time the compressor destroys itself and fills the system with acid. Then the compressor stops. It could during those times melt a wire loose and short for the housing (which could trip your house main breaker) or it may not. When the initial reason behind the failure was bad bearings creating the rotor to rub, then usually when the thing finally dies it will probably be shorted to the housing.
If this shorts to the housing, it can blow fuses and/or breakers and your ohmmeter will demonstrate an extremely low impedance from several windings to ground. If it will not short for the housing, then it will just stop. You still establish the sort of failure utilizing an ohmmeter.
You cannot directly diagnose a failed short with the ohmmeter unless it shorts for the housing – a shorted winding won’t appear with the ohmmeter although it would with an inductance meter (but who has among those?) Instead, you have to infer the failed short. You are doing this by establishing the the ohmmeter gives normal readings, the starter capacitor is good, power is arriving at the compressor, Plus an acid test in the freon shows acid present.
Having a failed short, just quit. Change everything, including the lines if at all possible. It is really not worth fixing; it is filled with acid and therefore is all junk. Further, a failed short could have been initially induced by some other failure within the system that caused a compressor overload; by replacing the whole system additionally you will remove that potential other problem.
Less commonly, a compressor could have a bearing failure, piston failure or a valve failure. These mechanical failures usually just signal wear out but tend to signal abuse (low lubricant levels, thermal limiter removed so compressor overheats, chronic low freon condition due to un-repaired leaks). More rarely, they could signal another failure within the system like a reversing valve problem or perhaps an expansion valve problem that winds up letting liquid freon enter into the suction side in the compressor.
When a bearing fails, usually you will know because the compressor will sound like a motor using a bad bearing, or it is going to lock up and refuse to operate. Within the worst case, the rotor will wobble, the windings will rub on the stator, and you will definitely find yourself using a failed short.
In the event the compressor locks up mechanically and fails to run, you will know because it will buzz very loudly for a couple seconds and may shudder (as with any stalled motor) till the thermal limiter cuts it off. When you do your electrical checks, you can find no evidence of failed open or failed short. The acid test will show no acid. In this case, you may consider using a hard-start kit however if the compressor has failed mechanically the hard-start kit won’t obtain the compressor to start out. In this instance, replacing the compressor is a great plan so long as the remainder of the method is not decrepit. After replacing the compressor, you have to carefully analyze the performance in the entire system to figure out whether or not the compressor problem was induced by something different.
Rarely, the compressor will experience a valve failure. In this case, it will either sit there and appear to run happily but will pump no fluid (valve won’t close), or it is going to lock up as a result of an lack of ability to move the fluid out from the compression chamber (valve won’t open). If it is running happily, then when you have established there is indeed plenty of freon in the system, but there is nothing moving, then you definitely have zero choice but to change the compressor. Again, a system with car which includes experienced a valve failure is a great candidate for a new compressor.
Now, in the event the compressor is mechanically locked up it could be because of a few things. In the event the compressor is on the heat pump, ensure the reversing valve is not stuck midway. Also ensure the expansion valve is working; when it is blocked it may lock the compressor. Also ensure the filter will not be clogged. I remember when i saw a system which had a locked compressor because of liquid lock. Some idiot had “serviced” the program with the addition of freon, and adding freon, and adding freon up until the thing was completely packed with liquid. Trust me; that does not work.
Should diagnosis show a clogged filter, then this needs to be taken as positive proof of some failure in the system Besides a compressor failure. Typically, it will be metal fragments from the compressor that clogs the filter. This may only happen if something is causing the compressor to put on very rapidly, especially in the pistons, the rings, the bores, and also the bearings. Either the compressor has vastly insufficient lubrication OR (and more commonly) liquid freon is getting into the compressor on the suction line. This behavior should be stopped. Glance at the expansion valve as well as at the reversing valve (for a heat pump).
Often an older system experiences enough mechanical wear internally that it is “worn in” and requires more torque to start out against the system load than may be delivered. This system will sound just like one having a locked bearing; the compressor will buzz loudly for a couple seconds then the thermal limiter will kill it. Occasionally, this method begins right up should you whack the compressor having a rubber mallet though it may be buzzing. This kind of system is a great candidate for a hard-start kit. This kit stores energy and, once the compressor is told to start out, dumps extra current to the compressor for any second approximately. This overloads the compressor, but gives some extra torque to get a limited time and is also often enough to create that compressor run again. We have had hard-start kits produce an added 8 or 9 years in a few old units that otherwise I would have been replacing. Conversely, I actually have had them give only a few months. It is actually your call, but considering how cheap a hard-start kit is, it is worth trying if the symptoms are as described.