Air conditioner compressors usually fail because of one of two conditions: time as well as hours of operation (wear out or abuse. There are some failures that can occur elsewhere within the system that can result in a compressor failure, however these are more uncommon unless the system has been substantially abused.
Usually abuse is because of extended running with improper freon charge, or as a consequence of improper service in the process. This improper service may include overcharging, undercharging, installing a bad 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 who had a significant burnout without taking proper steps to eliminate the acid through the system, installing the wrong compressor (not big enough) for that system, or installing ACcompressor on a system which had a few other failure which had been never diagnosed.
The compressor can fail in only a handful of different ways. It may fail open, fail shorted, experience a bearing failure, or even a piston failure (throw a rod), or experience a valve failure. That is pretty much the complete list.
Whenever a compressor fails open, a wire within the compressor breaks. This really is unserviceable and the symptom is that the compressor will not run, though it may hum. In the event the compressor fails open, and after the steps here fails to fix it, then this system might 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 method is not decrepit then it will be cost effective to simply put a whole new compressor in.
Testing for any failed open compressor is easy. Pop the electrical cover for that compressor off, and take away the wires and the thermal limiter. Employing an ohmmeter, measure the impedance from a single terminal to a different across all 3 terminals from the compressor. Also appraise the impedance towards the case from the compressor for those three terminals.
You should read low impedance values for many terminal to terminal connections (several hundred ohms or less) and you need to have a superior impedance (several kilo-ohms or greater) for those terminals for the case (which can be ground). If the terminal to terminal connections is a very high impedance, you have a failed open compressor. In unusual cases, a failed open compressor may show a minimal impedance to ground from one terminal (that will be one of many terminals related to the failed open). In cases like this, the broken wire has moved and is also contacting the situation. This condition – that is quite rare however, not impossible – might lead to a breaker to trip and can result in a misdiagnosis of failed short. Be cautious here; do an acid test of the items in the lines before deciding how to proceed with repair.
Each time a compressor fails short, what goes on is that insulation on the wires has worn off or burned off or broken inside the Showerhead. This enables a wire on a motor winding to touch something it ought to not touch – most often itself a turn or two further along on the motor winding. This results in a “shorted winding” which will stop the compressor immediately and cause it to heat up and burn internally.
Bad bearings can cause a failed short. Either the rotor wobbles enough get in touch with the stator, leading to insulation damage that shorts the rotor either to ground or to the stator, or end bearing wear can enable the stator to shift down over time until it starts to rub against the stator ends or the housing.
Usually when one of these brilliant shorts occur, it is far from immediately a hard short – which means initially the contact is intermittent and comes and goes. Every time the short occurs, the compressor torque drops sharply, the compressor may shudder a bit visibly consequently, and also this shudder shakes the winding enough to separate the short. As the short is in place, the existing through the shorted winding shoots up and plenty of heat is produced. Also, usually the short will blow some sparks – which produces acid inside vqxigq air conditioning unit system by decomposing the freon into a combination of hydrochloric and hydrofluoric acid.
With time (possibly a couple of weeks, usually less) the shuddering and also the sparking as well as the heat as well as the acid cause insulation to fail rapidly on the winding. Ultimately, the winding loses enough insulation that this inside the compressor is literally burning. This can only carry on for a couple minutes nevertheless in that point the compressor destroys itself and fills the system with acid. Then this compressor stops. It may during that time melt a wire loose and short for the housing (which can trip your property main breaker) or it may possibly not. In the event the initial reason behind the failure was bad bearings causing the rotor to rub, then usually if the thing finally dies it will likely be shorted towards the housing.
If this shorts for the housing, it is going to blow fuses and/or breakers and your ohmmeter shows a very low impedance from a number of windings to ground. When it does not short to the housing, it will just stop. You will still establish the type of failure using an ohmmeter.
You cannot directly diagnose a failed short with the ohmmeter unless it shorts to the housing – a shorted winding won’t show up with an ohmmeter even though it would with the inductance meter (but who has one of those particular?) Instead, you must infer the failed short. One does this by establishing the the ohmmeter gives normal readings, the starter capacitor is great, power is arriving at the compressor, Plus an acid test of the freon shows acid present.
Using a failed short, just stop trying. Change everything, including the lines when possible. It is not worth fixing; it is full of acid and for that reason is all junk. Further, a failed short might have been initially induced by a few other failure in the system that caused a compressor overload; by replacing the whole system additionally you will remove 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 could signal abuse (low lubricant levels, thermal limiter removed so compressor overheats, chronic low freon condition due to un-repaired leaks). More rarely, they can signal another failure within the system such as a reversing valve problem or an expansion valve problem that winds up letting liquid freon enter into the suction side in the compressor.
If a bearing fails, usually you will be aware since the compressor will sound like a motor with a bad bearing, or it is going to lock up and refuse to perform. In the worst, the rotor will wobble, the windings will rub on the stator, and you will definitely wind up with a failed short.
In the event the compressor locks up mechanically and fails to run, you will know as it will buzz very loudly for a couple of seconds and could shudder (just like any stalled motor) until the thermal limiter cuts it away. When you do your electrical checks, you will discover no evidence of failed open or failed short. The acid test will show no acid. In this instance, you may try a hard-start kit however, if the compressor has failed mechanically the hard-start kit won’t get the compressor to begin. In this instance, replacing the compressor is an excellent plan as long as all of those other product is not decrepit. After replacing the compressor, you have to carefully analyze the performance in the entire system to figure out whether the compressor problem was induced by something else.
Rarely, the compressor are experiencing a valve failure. In this case, it will either sit there and appear to run happily and definitely will pump no fluid (valve won’t close), or it is going to lock up because of an inability to move the fluid out of the compression chamber (valve won’t open). When it is running happily, then after you have established that there is definitely lots of freon inside the system, but nothing is moving, then you certainly do not have choice but to alter the compressor. Again, a system with truck which includes had a valve failure is an excellent candidate to get a new compressor.
Now, in the event the compressor is mechanically locked up it may be due to a few things. If the compressor is over a heat pump, ensure that the reversing valve is not stuck halfway. Also make sure the expansion valve is working; if it is blocked it could lock the compressor. Also ensure that the filter is not really clogged. I once saw a process which had a locked compressor because 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 does not work.
Should diagnosis show a clogged filter, then this ought to be taken as positive proof of some failure in the system Apart from a compressor failure. Typically, it will likely be metal fragments out from 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, as well as the bearings. Either the compressor has vastly insufficient lubrication OR (and much more commonly) liquid freon is becoming into the compressor on the suction line. This behavior has to be stopped. Consider the expansion valve and also at the reversing valve (for a heat pump).
Often an older system experiences enough mechanical wear internally that it is “worn in” and desires more torque to start out up against the system load than could be delivered. This technique will sound much like one having a locked bearing; the compressor will buzz loudly for a couple seconds then this thermal limiter will kill it. Occasionally, this technique begins right up if you whack the compressor using a rubber mallet though it may be buzzing. This type of system is a great candidate to get a hard-start kit. This kit stores energy and, if the compressor is told to start out, dumps extra current into the compressor to get a second or so. This overloads the compressor, but gives a little extra torque for a short period of time and is also often enough to help make that compressor run again. I have had hard-start kits produce an additional 8 or 9 years in certain old units that otherwise I could have been replacing. Conversely, I have had them give only some months. It is actually your call, but considering how cheap a tough-start kit is, it really is worth trying once the symptoms are as described.