Air conditioner compressors usually fail on account of 1 of 2 conditions: time and buisness hours (degrade), or abuse. There are a few failures which could occur elsewhere inside the system that may cause a compressor failure, but these are less common unless the internal system has long been substantially abused.
Usually abuse is usually a result of extended running with improper freon charge, and a consequence of improper service along the way. This improper service can include overcharging, undercharging, installing the improper starter capacitor instead, removing (as an alternative to repairing/replacing) the thermal limiter, insufficient oil, mixing incompatible oil types, or wrong oil, installing the compressor on a system that had a major burnout without taking proper steps to get rid of the acid coming from the system, installing the improper compressor (not big enough) for your system, or installing a fresh compressor on a system that had another failure or a never diagnosed.
The compressor can fail in only some other methods. It might fail open, fail shorted, experiencing a bearing failure, or maybe a piston failure (throw a rod), or have valve failure. That may be just about the entire list.
Whenever a compressor fails open, a wire contained in the compressor breaks. This is certainly unserviceable along with the symptom could be that the compressor will not run, though it may hum. In the event the compressor fails open, and implementing the steps here does not fix it, probably the system can be quite a good candidate for a new compressor. This failure causes no further failures and should not damage the remainder of the system; if the whole system is not decrepit in that acse might possibly be economical to simply create a new compressor in.
Testing to get a failed open compressor is simple. Pop the electrical cover for compressor off, and get rid of the wires along with the thermal limiter. Using an ohmmeter, measure the impedance to the next terminal to a different one across all three terminals of a typical compressor. Also measure the impedance towards the case of the compressor for those three terminals.
You should read low impedance values for all terminal to terminal connections (a number of hundred ohms or lower) and you ought to have a high impedance (several kilo-ohms or greater) for all terminals into the case (that's ground). If any of the terminal to terminal connections is an high impedance, you have a failed open compressor. In very rare cases, a failed open compressor may show a low impedance to ground from one particular terminal (which is able to be among the terminals involved with the service failed open). In such cases, the broken wire has moved and it is contacting how it is. This kind of migraines - and that is quite rare but not impossible - could cause a breaker to trip and could result in a misdiagnosis of failed short. Be cautious here; do an acid test of a typical veggies growing in the lines before deciding the best way to go ahead with repair.
Every time a compressor fails short, what happens is because insulation on the wires has worn off or burned off or broken inside the compressor. This allows a wire on a motor winding in touching something it must not touch - most likely itself a turn or two further along at the motor winding. This results in a "shorted winding" which can stop the compressor immediately and cause it to heat up and burn internally.
Bad bearings can cause a failed short. Either the rotor wobbles such that you can contact the stator, causing insulation damage that shorts the rotor either to ground or to the stator, or end bearing wear can allow the stator to shift above time until it begins to rub contrary to the stator ends as well as housing.
Usually when such a shorts occur, this is not immediately a hard short - basically initially the contact is intermittent and comes and goes. Every time the short occurs, the compressor torque drops sharply, the compressor may shudder a lttle bit visibly subsequently, and such shudder shakes the winding such that you could separate the short. While the short is in place, the present through the shorted winding shoots up plus a lot of heat is produced. Also, usually the short will blow some sparks - which produces acid included in the air conditioner system by decomposing the freon right into a mixture of hydrochloric and hydrofluoric acid.
Eventually (possibly a couple of weeks, usually less) the shuddering as well as the sparking as well as the heat and also the acid cause insulation to fail rapidly on your winding. Ultimately, the winding loses enough insulation that the inside of the compressor is literally burning. This would only keep on for a couple minutes however in this point the compressor destroys itself and fills the machine with acid. Probably the compressor stops. It could at that time melt a wire loose and short to the housing (which can trip your home main breaker) or it may not. If the initial reason behind the failure was bad bearings causing the rotor to rub, then usually whenever the thing finally dies it will be shorted to the housing.
Whether it shorts to the housing, it'll blow fuses and/or breakers and your ohmmeter will show an incredibly low impedance from one if not more windings to ground. Whether or not this doesn't short to the housing, in that acse will just stop. You continue to establish the type of failure using an ohmmeter.
Do not directly diagnose an unsuccessful short which includes an ohmmeter unless it shorts into the housing - a shorted winding won't show up with an ohmmeter although it would having inductance meter (but who has just like some of those?) Instead, you should infer the failed short. You attempt this by establishing the the ohmmeter gives normal readings, the starter capacitor is great, power is arriving along at the compressor, AND an acid test of the freon shows acid present.
By using a failed short, just give up. Change everything, including the lines if possible. It's not worth fixing; its rich in acid thus is all junk. Further, an unsuccessful short happens to be initially attributable to other failure in the system that caused a compressor overload; by replacing the whole system you furthermore may will look to lose that potential other problem.
Less commonly, a compressor are going to have bearing failure, piston failure or perhaps a valve failure. These mechanical failures usually just signal tire but could signal abuse (low lubricant levels, thermal limiter removed so compressor overheats, chronic low freon condition from un-repaired leaks). More rarely, they often signal another failure within the system say for example reversing valve problem or perhaps an expansion valve problem that winds up letting liquid freon get into the suction side of many compressor.
Should a bearing fails, usually you'll be safe in the knowledge for the reason that compressor will seem like a motor by using a bad bearing, or it will lock up and refuse to run. In the worst case, the rotor will wobble, the windings will rub in the stator, and you may wind up by using a failed short.
When the compressor locks up mechanically and fails to run, you'll be safe in the knowledge since it will buzz very loudly for a couple of seconds and will shudder (very much like any stalled motor) so that the thermal limiter cuts it off. After you do your electrical checks, you will discover no clue of failed open or failed short. The acid test will show no acid. In this instance, you would possibly consider a hard-start kit however if the compressor has failed mechanically the hard-start kit won't have the compressor to start. In such cases, replacing the compressor is an efficient plan long as the whole system is not decrepit. After replacing the compressor, you must carefully analyze behavior the entire system to determine whether the compressor problem was induced by something different.
Rarely, the compressor will experience a valve failure. In cases like this, it'll either sit there and appear to operate happily but pump no fluid (valve won't close), or it should lock up due to an inability to maneuver the fluid out from the compression chamber (valve won't open). If it is running happily, then once you have established that there is indeed a lot of freon inside the system, but nothing is moving, after this you have no choice but to alter the compressor. Again, a system by using a compressor which includes had a valve failure is an efficient candidate for only a new compressor.
Now, when the compressor is mechanically locked up it could be as a result of the only a few things. In the event the compressor is present in a heat pump, check to see if the reversing valve will never be stuck halfway. Also be certain expansion valve is working; if it's blocked it can lock the compressor. Also be certain filter is not really clogged. I once saw a system that had a locked compressor from liquid lock. Some idiot had "serviced" sst by adding freon, and adding freon, and adding freon before thing was completely full of liquid. Trust me; that doesn t work.
Should diagnosis show a clogged filter, then this is necessary as positive evidence of some failure throughout system In addition to a compressor failure. Typically, it will likely be metal fragments out of the compressor that clogs the filter. This might only happen if something is generating the compressor dress in very rapidly, particularly in the pistons, the rings, the bores, and also the bearings. Either the compressor has vastly insufficient lubrication OR (and many more commonly) liquid freon starting to get into your compressor in the suction line. This behavior must be stopped. Look at the expansion valve and at the reversing valve (for only a heat pump).
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Often air conditioner compressor cost an aging system experiences enough mechanical wear internally that you should "worn in" and desires more torque to start out against the system load than may well be delivered. This strategy will sound same as one with a locked bearing; the compressor will buzz loudly for a couple of seconds then a thermal limiter will kill it. Occasionally, this strategy will start right up if you whack the compressor with a rubber mallet even though it is buzzing. That system is an outstanding candidate to get a hard-start kit. This kit stores energy and, when the compressor is told to start, dumps extra current on the compressor to have a second or so. This overloads the compressor, but gives some extra torque for a limited time and is often such that you can give that compressor run again. I actually have had hard-start kits give me one additional 8 or 9 years in some old units that otherwise I would have been replacing. Conversely, I have had them give only some months. It s your call, but considering how cheap a hard-start kit is, it truly is worth trying in the event the transmissions for sale symptoms are as described.
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