Air conditioner compressors usually fail resulting from one of two conditions: some time 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 machine is substantially abused.
Usually abuse is really an effect of extended running with improper freon charge, or as as a result of improper service as i advanced. This improper service consist of overcharging, undercharging, installing the unhealthy starter capacitor as a substitute, removing (rather than 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 handful of alternative ways. It could fail open, fail shorted, end up with bearing failure, or perhaps a piston failure (throw a rod), or experience a valve failure. That is pretty much the full list.
Every time a compressor fails open, a wire stored by the compressor breaks. This can be unserviceable as well as the symptom would be that the compressor does not run, although it may hum. If the compressor fails open, and using the steps here will not fix it, then the system could be a good candidate to have a new compressor. This failure causes no further failures and won'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 place 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 (which is ground). If any of a typical terminal to terminal connections is a really high impedance, you own a failed open compressor. In very rare cases, an unsuccessful open compressor may show a low impedance to ground from a place terminal (which will be among the many terminals concerned failed open). In this instance, the broken wire has moved and is also contacting the reality. This condition - which is certainly quite rare however not impossible - might lead to a breaker to trip and can cause a misdiagnosis of failed short. Take care here; do an acid test of the contents of the lines before deciding the way to go ahead with repair.
When a compressor fails short, what happens is that insulation at the wires has worn off or burned off or broken included in the compressor. This lets a wire for the motor winding touching something it should not touch - most commonly itself a turn or two further along in the motor winding. This can result within a "shorted winding" that may stop the compressor immediately and cause it to warm up and burn internally.
Bad bearings may cause an unsuccessful short. Either the rotor wobbles sufficiently to contact the stator, leading to insulation damage that shorts the rotor either to ground or else towards the stator, or end bearing wear can allow the stator to shift down over time until it begins to rub against the stator ends and even the housing.
Usually when a sample shorts occur, it is not immediately a difficult short - essentially initially the contact is intermittent and comes and goes. Each and every time the short occurs, the compressor torque drops sharply, the compressor may shudder a bit visibly consequently, so that shudder shakes the winding such that you can separate the short. Although short is present in place, the existing throughout the shorted winding shoots up along with a large amount of heat is produced. Also, usually the short will blow some sparks - that generates acid stored by the air conditioner system by decomposing the freon with a mixture of hydrochloric and hydrofluoric acid.
Over time (possibly an a few weeks, usually less) the shuddering and also the sparking along with the heat along with the acid cause insulation to fail rapidly on the winding. Ultimately, the winding loses enough insulation the fact that around the compressor is literally burning. This will likely only go on only a few minutes yet in that time the compressor destroys itself and fills the internal system with acid. Then the compressor stops. It will probably then melt a wire loose and short to your housing (which could trip the house main breaker) or it might not. In the event the initial reason for the failure was bad bearings causing the rotor to rub, then usually while the thing finally dies it is going to be shorted into the housing.
When it shorts to your housing, it should blow fuses and/or breakers along with your ohmmeter will show an exceptionally low impedance to the next or more windings to ground. If it will not short to your housing, then it may will just stop. You establish the brand of failure using an ohmmeter.
You will never directly diagnose a failed short having ohmmeter unless it shorts to your housing - a shorted winding won't be displayed which includes an ohmmeter even if it would with an inductance meter (but who has a kind of?) Instead, you will need to infer the failed short. Be done this by establishing the the ohmmeter gives normal readings, the starter capacitor is an useful one, power is arriving for the compressor, AND an acid test of a typical freon shows acid present.
That has a failed short, just hand over. Change everything, which includes lines if at all possible. It isn't worth fixing; it truly is filled with acid and as such is all junk. Further, a failed short might have been initially induced by another failure inside the system that caused a compressor overload; by replacing the whole system additionally you will get rid of that potential other problem.
Less commonly, a compressor is going to have a bearing failure, piston failure or maybe a valve failure. These mechanical failures usually just signal degrade 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 could signal another failure throughout system such as a reversing valve problem or expansion valve problem that winds up letting liquid freon experience the suction side of your compressor.
If a bearing fails, usually you will have the comfort of knowing due to the reason that the compressor will be understood as a motor that has a bad bearing, or it should lock up and refuse to perform. Inside the worst case, the rotor will wobble, the windings will rub at the stator, and you'll find yourself that has a failed short.
In case the compressor locks up mechanically and fails to run, you will have the comfort of knowing this is because will buzz very loudly for a couple seconds and might shudder (identical to any stalled motor) until the thermal limiter cuts it off. When you does your electrical checks, you will find no evidence of failed open or failed short. The acid test will show no acid. In such cases, you might try out hard-start kit but in case compressor has failed mechanically the hard-start kit won't receive the compressor to start out. In this instance, replacing the compressor is an excellent plan such a long time when the remainder of the system is not decrepit. After replacing the compressor, you should carefully analyze overall performance the full system to determine whether the compressor problem was attributable to something else.
Rarely, the compressor will experience a valve failure. In this case, it will of course either sit there and appear to own happily but will pump no fluid (valve won't close), or it will lock up from an inability to relocate the fluid from the compression chamber (valve won't open). If it's running happily, then after you have established that there's indeed tons of freon in the system, but nothing is moving, then you definitely do not have a choice yet to refresh the compressor. Again, a system that has a compressor which has enjoyed a valve failure is a good candidate to get a new compressor.
Now, in case the compressor is mechanically locked up it may be due to the couple of things. If the compressor is on a heat pump, make sure the reversing valve is not really stuck half way. Also be certain the expansion valve is working; if it is blocked it may lock the compressor. Also be certain the filter will never be clogged. I once saw a system that had a locked compressor due to liquid lock. Some idiot had "serviced" the system by adding freon, and adding freon, and adding freon till the thing was completely full of liquid. Trust me; that does not work.
Should diagnosis show a clogged filter, the is important as positive a history of some failure within the system OTHER than a compressor failure. Typically, it will be metal fragments away from the compressor that clogs the filter. This can only happen if something is causing the compressor to don very rapidly, particularly inside the 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 at the suction line. This behavior need to be stopped. Try to find 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 is "worn in" and demands 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 for a couple 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 the compressor for a second or thereabouts. This overloads the compressor, but gives some extra torque to have a short period of time which is often such that you could honor 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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