Air conditioner compressors usually fail due to one of two conditions: period and hours of operation (wear out), or abuse. There are some failures that could occur elsewhere within the system which will cause a compressor failure, but these are less common unless the system continues to be substantially abused.
Usually abuse is known as an are the effect of extended running with improper freon charge, or because of improper service as i progressed. This improper service may incorporate overcharging, undercharging, installing the wrong starter capacitor as a replacement, removing (instead of repairing/replacing) the thermal limiter, insufficient oil, mixing incompatible oil types, or wrong oil, installing the compressor on an system that had a big burnout without taking proper steps to remove the acid out of your system, installing the wrong compressor (not big enough) for the system, or installing a brand new compressor on an system that had some other failure that was never diagnosed.
The compressor can fail in exclusively a few other ways. It may fail open, fail shorted, have bearing failure, or even a piston failure (throw a rod), or end up with valve failure. That's pretty well the entire list.
Whenever a compressor fails open, a wire inside the compressor breaks. This is often unserviceable and also the symptom is the factthat the compressor will not run, even if it may hum. When the compressor fails open, and following the steps here won't fix it, then a system might be a good candidate for only a new compressor. This failure causes no further failures and shouldn't damage the remainder of the system; in case the rest of the system is not decrepit and then it could be affordable to just imposed a new compressor in.
Testing for a failed open compressor is easy. Pop the electrical cover of the compressor off, and take away the wires and also the thermal limiter. Using an ohmmeter, measure the impedance from a place terminal to a different across all 3 terminals of your compressor. Also measure the impedance to your case of the compressor for all those three terminals.
It is best to read low impedance values for those terminal to terminal connections (several hundred ohms or even lesser) and you should have a high impedance (several kilo-ohms or greater) for those terminals to the case (and that is ground). If any of many terminal to terminal connections is a very high impedance, you've got a failed open compressor. In very rare cases, a failed open compressor may show a low impedance to ground to the next terminal (which can be one of the terminals associated with the failed open). In cases like this, the broken wire has moved and is contacting the case. This condition - which is quite rare though not impossible - could potentially cause a breaker to trip and shall spark a misdiagnosis of failed short. Be careful here; do an acid test of your produce in the lines before deciding how you can proceed with repair.
Each time a compressor fails short, what happens is the idea that insulation in the wires has worn off or burned off or broken stored by the compressor. This lets a wire on an motor winding to the touch something it should't touch - most typically itself a turn or two further along on the motor winding. This brings on inside of a "shorted winding" which can stop the compressor immediately and cause it to get hot and burn internally.
Bad bearings could potentially cause a failed short. Either the rotor wobbles enough to 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 or the housing.
Usually when one of these shorts occur, it's not immediately hard drive data short - therefore initially the contact is intermittent and comes and goes. When the short occurs, the compressor torque drops sharply, the compressor may shudder somewhat visibly subsequently, and such shudder shakes the winding such that you could separate the short. Even though the short posesses place, the current in the shorted winding shoots up as well as a lot of heat is produced. Also, usually the short will blow some sparks - which produces acid contained in the air conditioner system by decomposing the freon right into a mixture of hydrochloric and hydrofluoric acid.
As time passes (possibly a very few weeks, usually less) the shuddering and the sparking and the heat as well as the acid cause insulation to fail rapidly at the winding. Ultimately, the winding loses enough insulation which the surrounding the compressor is literally burning. This can only look for a few minutes but in at that moment the compressor destroys itself and fills sst with acid. Then a compressor stops. It may at that time melt a wire loose and short to the housing (what can trip your house main breaker) or towards the. In case the initial cause of the failure was bad bearings causing the rotor to rub, then usually in the event the thing finally dies it is shorted towards the housing.
If it shorts towards the housing, it will blow fuses and/or breakers with your ohmmeter will show an extremely low impedance from one particular if not more windings to ground. Whether it does not short towards the housing, and then it will just stop. You still establish the structure of failure using an ohmmeter.
You cannot directly diagnose a failed short with an ohmmeter unless it shorts to the housing - a shorted winding won't come up who has an ohmmeter while it would having inductance meter (but who has just like some of those?) Instead, you should infer the failed short. You try this by establishing the the ohmmeter gives normal readings, the starter capacitor is great, power is arriving with 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 probably. It's not worth fixing; it is packed with acid thus is all junk. Further, an unsuccessful short has been initially attributable to other failure in the system that caused a compressor overload; by replacing the whole system you also will look to lose that potential other problem.
Less commonly, a compressor are going to have bearing failure, piston failure or 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 on account of un-repaired leaks). More rarely, they will be able to signal another failure within the system say for example a reversing valve problem or perhaps an expansion valve problem that winds up letting liquid freon get into the suction side of many compressor.
In case a bearing fails, usually you will know for the reason that compressor will seem like a motor by using a bad bearing, or it will lock up and refuse to own. In the worst case, the rotor will wobble, the windings will rub on your stator, and you will find themselves with a failed short.
When the compressor locks up mechanically and fails to run, you'll be safe in the knowledge because it will buzz very loudly only a few seconds and may shudder (very much like any stalled motor) so that the thermal limiter cuts it off. Once 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 test 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 effective plan long as the whole system is not decrepit. After replacing the compressor, you have to 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 this instance, it'll either sit there and appear to run happily but pump no fluid (valve won't close), or it should lock up resulting from an inability to maneuver the fluid out from the compression chamber (valve won't open). Should it be running happily, then when you have established that there is indeed plenty of freon within the system, but nothing is moving, after this you not have the choice but to alter the compressor. Again, a system with a compressor having had a valve failure is an effective candidate for only a new compressor.
Now, if the compressor is mechanically locked up it could be as a result of the a few things. In the event the compressor is present in a heat pump, check to see if the reversing valve will not be stuck midway. Also be certain expansion valve is working; whether it is blocked it can lock the compressor. Also be certain filter is not 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 so that the thing was completely full of liquid. Trust me; that doesn t work.
Should diagnosis show a clogged filter, then an is necessary as positive evidence of some failure throughout system Except a compressor failure. Typically, it will likely be metal fragments out from the compressor that clogs the filter. This may only happen if something is generating the compressor dress in very rapidly, particularly in the pistons, the rings, the bores, as well as the bearings. Either the compressor has vastly insufficient lubrication OR (and even more commonly) liquid freon is becoming into the compressor on your suction line. This behavior must be stopped. Look at the expansion valve and at the reversing valve (to have 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 begin the actual system load than might be delivered. This regime will sound same as a car battery with a locked bearing; the compressor will buzz loudly for a couple of seconds then a thermal limiter will kill it. Occasionally, this regime will start right up if you whack the compressor that has a rubber mallet while it is buzzing. A very system is an outstanding candidate for a hard-start kit. This kit stores energy and, while the compressor is told to start, dumps extra current on the compressor to get a second or so. This overloads the compressor, but gives some extra torque for a small amount of time and is often enough to give that compressor run again. I have had hard-start kits give me one additional 8 or 9 years in certain old units that otherwise I usually are actually replacing. Conversely, I have had them give just a couple of months. It's your call, but considering how cheap a hard-start kit is, it really is worth trying in the event the transmissions for sale symptoms are as described.
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