Air conditioner compressors usually fail resulting from one of two conditions: period and hours of operation (tire), or abuse. There are numerous failures that may occur elsewhere in the system that will cause a compressor failure, but these are less common unless the system is substantially abused.
Usually abuse is really an are the effect of extended running with improper freon charge, or as as a result of improper service as i progressed. This improper service consist of overcharging, undercharging, installing the unhealthy starter capacitor as a substitute, removing (instead of repairing/replacing) the thermal limiter, insufficient oil, mixing incompatible oil types, or wrong oil, installing the compressor at the system that had a great burnout without taking proper steps to take off the acid from the system, installing the unhealthy compressor (not meet the minimum quanity requirements) for system, or installing a new compressor at the system that had other failure or perhaps a never diagnosed.
The compressor can fail in particularly a few alternative ways. It could fail open, fail shorted, end up with bearing failure, or even a piston failure (throw a rod), or experience a valve failure. That is pretty much comprehensive list.
When a compressor fails open, a wire inside the compressor breaks. This can be unserviceable as well as the symptom would be that the compressor doesn't run, even if it may hum. If the compressor fails open, and using the steps here will not fix it, then a system could be a good candidate to have a new compressor. This failure causes no further failures and shouldn't damage the rest of the system; in the event the remainder of the system is not decrepit then it will be cost effective to merely imposed a new compressor in.
Testing for only a failed open compressor commonly be installed. Pop the electrical cover for your compressor off, and remove the wires as well as the thermal limiter. Using an ohmmeter, measure the impedance from one terminal to another across all of them terminals of the compressor. Also measure the impedance into the case of the compressor for many three terminals.
You ought to read low impedance values for all those terminal to terminal connections (a few hundred ohms or fewer) and you will have a great impedance (several kilo-ohms or greater) for all those terminals towards the case (and that is ground). If any of a typical terminal to terminal connections is a really high impedance, you've got a failed open compressor. In very rare cases, an unsuccessful open compressor may show a low impedance to ground from a place terminal (which can be among the many terminals concerned failed open). In cases like this, the broken wire has moved and is also contacting the case. This condition - which is certainly quite rare however not impossible - might lead to a breaker to trip and shall cause a misdiagnosis of failed short. Take care here; do an acid test of your items in the lines before deciding how you can proceed with repair.
Whenever a compressor fails short, what happens may be that insulation on your wires has worn off or burned off or broken included in the compressor. This lets a wire at the motor winding to touch something it shouldn t touch - most typically itself a turn or two further along in the motor winding. This can result inside a "shorted winding" which will stop the compressor immediately and cause it to generate heat and burn internally.
Bad bearings could cause an unsuccessful short. Either the rotor wobbles such that you could contact the stator, ending in insulation damage that shorts the rotor either to ground or else towards the stator, or end bearing wear can allow the stator to shift over time until it begins to rub on the stator ends and the housing.
Usually when a sample shorts occur, it is not immediately hard drive data short - meaning that initially the contact is intermittent and comes and goes. When the short occurs, the compressor torque drops sharply, the compressor may shudder a bit visibly because of this, and this shudder shakes the winding sufficiently to separate the short. Even though the short is contained in place, the current from the shorted winding shoots up and a number of heat is produced. Also, usually the short will blow some sparks - which produces acid inside the air conditioner system by decomposing the freon into a mixture of hydrochloric and hydrofluoric acid.
As time passes (possibly an only a few weeks, usually less) the shuddering along with the sparking and the heat and the acid cause insulation to fail rapidly at the winding. Ultimately, the winding loses enough insulation the fact that across the compressor is literally burning. This will only go on for a couple of minutes yet in that point the compressor destroys itself and fills the internal system with acid. Then a compressor stops. It will afterward melt a wire loose and short towards the housing (what can trip your own home main breaker) or may possibly not. In the event the initial explanation for the failure was bad bearings causing the rotor to rub, then usually when the thing finally dies it will likely be shorted to your housing.
When it shorts towards the housing, it will of course blow fuses and/or breakers plus your ohmmeter will show a very low impedance to the next or even more windings to ground. Whether it won't short to your housing, then it will just stop. Yourself establish the brand of failure using an ohmmeter.
You cannot directly diagnose a failed short who has an ohmmeter unless it shorts towards the housing - a shorted winding won't display having ohmmeter though it would which includes an inductance meter (but who has a type of?) Instead, you have to infer the failed short. Be done this by establishing the the ohmmeter gives normal readings, the starter capacitor is good, power is arriving with the compressor, AND an acid test of many freon shows acid present.
With a failed short, just stop trying. Change everything, such as the lines if at all possible. It is not worth fixing; it is filled with acid and therefore is all junk. Further, a failed short might have been initially a result of a few other failure throughout system that caused a compressor overload; by replacing the whole system additionally you will earn cleared of that potential other problem.
Less commonly, a compressor are having bearing failure, piston failure or a valve failure. These mechanical failures usually just signal give up but could signal abuse (low lubricant levels, thermal limiter removed so compressor overheats, chronic low freon condition due to un-repaired leaks). More rarely, they will be able to signal another failure in the system say for example a reversing valve problem or maybe an expansion valve problem that winds up letting liquid freon get involved in the suction side of a typical compressor.
If a bearing fails, usually you will know because the compressor will sound like a motor with a bad bearing, or it will of course lock up and refuse to own. Throughout worst case, the rotor will wobble, the windings will rub at the stator, and you will find yourself with a failed short.
If the compressor locks up mechanically and fails to run, you will know this is because will buzz very loudly for a couple seconds and may shudder (same as any stalled motor) till the thermal limiter cuts it off. When you do your electrical checks, you will see no evidence of failed open or failed short. The acid test will show no acid. In this case, you may test a hard-start kit but if the compressor has failed mechanically the hard-start kit won't get the compressor to begin with. In cases like this, replacing the compressor is a good plan that long since the rest of the system is not decrepit. After replacing the compressor, you have to carefully analyze the performance of comprehensive system to determine whether the compressor problem was due to another thing.
Rarely, the compressor will experience a valve failure. In this case, it will either sit there and appear to run happily but is going to pump no fluid (valve won't close), or it'll lock up resulting from an inability to move the fluid away from the compression chamber (valve won't open). Should it be running happily, then upon getting established that there's indeed tons of freon within the system, but nothing is moving, you then do not have a choice nonetheless change the compressor. Again, a system that has a compressor having included a valve failure is a good candidate to have a new compressor.
Now, in case the compressor is mechanically locked up possibly because of the a few things. When the compressor is in a heat pump, be certain reversing valve will not be stuck half way. Also make sure the expansion valve is working; if it is blocked it might lock the compressor. Also make sure the filter is not clogged. I once saw a system that had a locked compressor on account of liquid lock. Some idiot had "serviced" the internal system by adding freon, and adding freon, and adding freon till the thing was completely full of liquid. Trust me; that doesn't work.
Should diagnosis show a clogged filter, then a should be taken as positive a history of some failure inside the system Except a compressor failure. Typically, it is going to be metal fragments away from the compressor that clogs the filter. This may only happen if something is producing the compressor to dress in very rapidly, particularly throughout pistons, the rings, the bores, and the bearings. Either the compressor has vastly insufficient lubrication OR (and a lot more commonly) liquid freon is getting directly into compressor on your suction line. This behavior needs to be stopped. Consider the expansion valve and at the reversing valve (to get a heat pump).
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Often air conditioner compressor cost a not-needed system experiences enough mechanical wear internally that it must be "worn in" and needs more torque to start contrary to the system load than can be delivered. This method will sound just like a replacement battery with a locked bearing; the compressor will buzz loudly only a few seconds later the thermal limiter will kill it. Occasionally, this method will kick off right up if you happen to whack the compressor which has a rubber mallet although it is buzzing. Such a system is a superb candidate for only a hard-start kit. This kit stores energy and, whenever the compressor is told to do start, dumps extra current into your compressor for a second or until comfortable. This overloads the compressor, but gives some extra torque for only a short period of time and is also often such that you could make that compressor run again. We have had hard-start kits give me an additional 8 or 9 years in most old units that otherwise I would personally seem to have been replacing. Conversely, I even have had them give only a few months. It is your call, but considering how cheap a hard-start kit is, its worth trying while the transmissions for sale symptoms are as described.
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