Air conditioner compressors usually fail due to one of two conditions: time and hours of operation (wear out or abuse. There are several failures that may occur elsewhere in the system that will cause a compressor failure, but these are less common unless the system has been substantially abused.
Usually abuse is caused by extended running with improper freon charge, or because of improper service as you go along. This improper service may include overcharging, undercharging, installing the wrong 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 on the system which had a major burnout without taking proper steps to eliminate the acid from the system, installing a bad compressor (too small) for the system, or installing air conditioner compressor over a system which had a few other failure that was never diagnosed.
The compressor can fail within just a handful of different ways. It could fail open, fail shorted, experience a bearing failure, or even a piston failure (throw a rod), or experience a valve failure. That is really the whole list.
Each time a compressor fails open, a wire in the compressor breaks. This really is unserviceable and the symptom is the fact that compressor does not run, though it may hum. When the compressor fails open, and pursuing the steps here will not correct it, then your system may be a good candidate to get a new compressor. This failure causes no further failures and won’t damage the remainder of the system; if the rest of the system is not decrepit then it would be cost effective to simply put a new compressor in.
Testing to get a failed open compressor is easy. Pop the electrical cover for the compressor off, and take away the wires as well as the thermal limiter. Utilizing an ohmmeter, measure the impedance from one terminal to another across the 3 terminals of the compressor. Also measure the impedance for the case of the compressor for all three terminals.
You should read low impedance values for many terminal to terminal connections (several hundred ohms or less) and you ought to have a great impedance (several kilo-ohms or greater) for all terminals for the case (which is ground). If any of the terminal to terminal connections is an extremely high impedance, you have a failed open compressor. In unusual cases, a failed open compressor may show a minimal impedance to ground in one terminal (that will be one of many terminals linked to the failed open). In cases like this, the broken wire has moved and it is contacting the truth. This condition – that is quite rare but not impossible – might cause a breaker to trip and may result in a misdiagnosis of failed short. Be cautious here; do an acid test from the valuables in the lines before deciding how you can proceed with repair.
Each time a compressor fails short, what happens is the fact that insulation on the wires has worn off or burned off or broken within the shower faucet. This permits a wire on a motor winding to touch something it must not touch – most commonly 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 up and burn internally.
Bad bearings may cause a failed short. Either the rotor wobbles enough get in touch with 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 over time until it starts to rub up against the stator ends or even the housing.
Usually when one of those shorts occur, it is really not immediately a difficult short – meaning 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 this shudder shakes the winding enough to separate the short. Whilst the short is within place, the present with the shorted winding shoots up and lots of heat is produced. Also, usually the short will blow some sparks – which produces acid inside vqxigq ac unit system by decomposing the freon into a combination of hydrochloric and hydrofluoric acid.
Over time (possibly a couple of weeks, usually less) the shuddering as well as the sparking and the heat as well as the acid cause insulation to fail rapidly on the winding. Ultimately, the winding loses enough insulation that this within the compressor is literally burning. This can only carry on for a few minutes but in that period the compressor destroys itself and fills the program with acid. Then your compressor stops. It might at that time melt a wire loose and short to the housing (which could trip your home main breaker) or it may not. When the initial reason for the failure was bad bearings creating the rotor to rub, then usually when the thing finally dies it will be shorted towards the housing.
If this shorts to the housing, it can blow fuses and/or breakers as well as your ohmmeter will demonstrate a really low impedance from several windings to ground. If it does not short to the housing, it will just stop. You continue to establish the sort of failure employing an ohmmeter.
You can not directly diagnose a failed short having an ohmmeter unless it shorts towards the housing – a shorted winding won’t show up with an ohmmeter although it would having an inductance meter (but who may have one of those?) Instead, you need to infer the failed short. You do this by establishing the the ohmmeter gives normal readings, the starter capacitor is great, power is reaching the compressor, AND an acid test from the freon shows acid present.
With a failed short, just stop trying. Change everything, like the lines when possible. It is far from worth fixing; it is filled with acid and therefore is actually all junk. Further, a failed short could have been initially induced by various other failure inside the system that caused a compressor overload; by replacing the entire system in addition, you will eliminate that potential other problem.
Less commonly, a compressor may have a bearing failure, piston failure or even 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 in the system for instance a reversing valve problem or even an expansion valve problem that winds up letting liquid freon go into the suction side in the compressor.
In case a bearing fails, usually you will understand since the compressor will sound like a motor with a bad bearing, or it will lock up and refuse to run. In the worst, the rotor will wobble, the windings will rub on the stator, and you will definitely wind up having a failed short.
In the event the compressor locks up mechanically and fails to operate, you will be aware because it will buzz very loudly for a few seconds and may shudder (just like any stalled motor) up until the thermal limiter cuts them back. Once you do your electrical checks, you can find no proof of failed open or failed short. The acid test shows no acid. In this instance, you may use a hard-start kit but if the compressor has failed mechanically the hard-start kit won’t obtain the compressor to start out. In this case, replacing the compressor is an excellent plan as long as the remainder of the product is not decrepit. After replacing the compressor, you have to carefully analyze the performance from the entire system to figure out whether or not the compressor problem was induced by another thing.
Rarely, the compressor will experience a valve failure. In this instance, it is going to either sit there and seem to run happily and can pump no fluid (valve won’t close), or it will lock up as a result of an lack of ability to move the fluid out from the compression chamber (valve won’t open). When it is running happily, then after you have established there is actually lots of freon in the system, but nothing is moving, then you have no choice but to alter the compressor. Again, a process with auto which includes enjoyed a valve failure is an excellent candidate to get a new compressor.
Now, if the compressor is mechanically locked up it may be because of couple of things. When the compressor is on the heat pump, ensure that the reversing valve is not really stuck halfway. Also ensure that the expansion valve is working; should it be blocked it may lock the compressor. Also ensure that the filter is not really clogged. I once saw a method that had a locked compressor as a result of liquid lock. Some idiot had “serviced” the system with the help of freon, and adding freon, and adding freon until the thing was completely full of liquid. Trust me; that will not work.
Should diagnosis show a clogged filter, then this ought to be taken as positive proof some failure in the system Apart from a compressor failure. Typically, it will likely be metal fragments out of the compressor that clogs the filter. This can only happen if something is bringing about 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 to the compressor on the suction line. This behavior has to be stopped. Glance at the expansion valve and also at the reversing valve (for any heat pump).
Often an older system experiences enough mechanical wear internally that it is “worn in” and needs more torque to begin from the system load than could be delivered. This system will sound the same as one having a locked bearing; the compressor will buzz loudly for a couple of seconds then this thermal limiter will kill it. Occasionally, this method will start right up in the event you whack the compressor having a rubber mallet even though it is buzzing. This kind of system is an excellent candidate for any hard-start kit. This kit stores energy and, if the compressor is told to start, dumps extra current to the compressor to get a second or so. This overloads the compressor, but gives a little extra torque to get a limited time and it is often enough to help make that compressor run again. I have had hard-start kits produce an extra 8 or 9 years in certain old units that otherwise I might have been replacing. Conversely, I actually have had them give only a few months. It is your call, but considering how cheap a hard-start kit is, it is actually truly worth trying once the symptoms are as described.