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 may occur elsewhere within the system that can cause a compressor failure, however these are more uncommon unless the system has been substantially abused.
Usually abuse is caused by extended running with improper freon charge, or because of improper service along the way. This improper service might 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 which had a major burnout without taking proper steps to get rid of the acid from the system, installing the wrong compressor (not big enough) 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 number of different ways. It can fail open, fail shorted, experience a bearing failure, or perhaps a piston failure (throw a rod), or experience a valve failure. That is pretty much the entire list.
Whenever a compressor fails open, a wire inside the compressor breaks. This is unserviceable and also the symptom is that the compressor fails to run, although it may hum. If the compressor fails open, and pursuing the steps here will not fix it, then your system can be a good candidate to get a new compressor. This failure causes no further failures and won’t damage all of those other system; if the remainder of the product is not decrepit then it would be economical to just put a whole new compressor in.
Testing for a failed open compressor is not hard. Pop the electrical cover for that compressor off, and take away the wires and also the thermal limiter. Employing an ohmmeter, look at the impedance from one terminal to another across all 3 terminals in the compressor. Also look at the impedance for the case from the compressor for many three terminals.
You ought to read low impedance values for all terminal to terminal connections (several hundred ohms or less) and you should have a great impedance (several kilo-ohms or greater) for all terminals for the case (which can be ground). If the terminal to terminal connections is an extremely high impedance, you have a failed open compressor. In rare cases, a failed open compressor may show a minimal impedance to ground from a single terminal (that will be among the terminals related to the failed open). In cases like this, the broken wire has moved and is also contacting the case. This problem – that is quite rare although 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 from the contents of the lines before deciding how you can proceed with repair.
When a compressor fails short, what goes on is the fact that insulation on the wires has worn off or burned off or broken inside the Bathtub Faucet. This enables a wire on the motor winding to touch something it should not touch – most often itself a turn or two further along on the motor winding. This results in a “shorted winding” that will stop the compressor immediately and make it heat up and burn internally.
Bad bearings can cause a failed short. Either the rotor wobbles enough to contact the stator, causing insulation damage that shorts the rotor either to ground or the stator, or end bearing wear can permit the stator to shift over time until it begins to rub up against the stator ends or even the housing.
Usually when one of those shorts occur, it is far from 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 somewhat visibly because of this, and this shudder shakes the winding enough to separate the short. While 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 mixture of hydrochloric and hydrofluoric acid.
As time passes (possibly a few 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 the inside of the compressor is burning. This can only go on for a few minutes but in that time the compressor destroys itself and fills the device with acid. Then your compressor stops. It may during those times melt a wire loose and short towards the housing (which can trip your property main breaker) or it may not. If the initial cause of the failure was bad bearings causing 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 will blow fuses and breakers and your ohmmeter shows a very low impedance from a number of windings to ground. If it fails to short for the housing, this will just stop. You still establish the sort of failure using an ohmmeter.
You are unable to directly diagnose a failed short with an ohmmeter unless it shorts for the housing – a shorted winding won’t turn up with an ohmmeter though it would having an inductance meter (but that has one of those?) Instead, you need to infer the failed short. You are doing this by establishing the the ohmmeter gives normal readings, the starter capacitor is good, power is coming to the compressor, As well as an acid test from the freon shows acid present.
Having a failed short, just quit. Change everything, like the lines when possible. It is not worth fixing; it is loaded with acid and for that reason is actually all junk. Further, a failed short could have been initially induced by a few other failure within the system that caused a compressor overload; by replacing the whole system additionally you will remove that potential other problem.
Less commonly, a compressor could have a bearing failure, piston failure or perhaps 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 because of un-repaired leaks). More rarely, they can signal another failure in the system like a reversing valve problem or perhaps an expansion valve problem that winds up letting liquid freon enter into the suction side from the compressor.
If a bearing fails, usually you will know as the compressor will seem to be a motor 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 on the stator, and you may end up using a failed short.
If the compressor locks up mechanically and fails to perform, you will know as it will buzz very loudly for a couple of seconds and may shudder (just like any stalled motor) until the thermal limiter cuts it off. Once you do your electrical checks, you will find no evidence of failed open or failed short. The acid test will show no acid. In this instance, you may use a hard-start kit however if the compressor has failed mechanically the hard-start kit won’t obtain the compressor to start. In this case, replacing the compressor is a good plan as long as all of those other method is not decrepit. After replacing the compressor, you must carefully analyze the performance in the entire system to find out if the compressor problem was induced by something else.
Rarely, the compressor are experiencing a valve failure. In cases like this, it will either sit there and seem to run happily and can pump no fluid (valve won’t close), or it is going to lock up as a result of an lack of ability to move the fluid out from the compression chamber (valve won’t open). If it is running happily, then after you have established that there is indeed a lot of freon within the system, but there is nothing moving, then you certainly do not have choice but to alter the compressor. Again, a system with car which includes enjoyed a valve failure is a great candidate for any new compressor.
Now, when the compressor is mechanically locked up it could be due to a couple of things. In the event the compressor is on a heat pump, ensure that the reversing valve is not stuck half way. Also make sure the expansion valve is working; should it be blocked it may lock the compressor. Also ensure that the filter is not really clogged. I remember when i saw a process who had a locked compressor as a result of liquid lock. Some idiot had “serviced” the program by adding freon, and adding freon, and adding freon till the thing was completely filled with liquid. Believe me; that will not work.
Should diagnosis show a clogged filter, then this should be taken as positive proof of some failure inside the system Besides a compressor failure. Typically, it will be metal fragments out of the compressor that clogs the filter. This could only happen if something causes the compressor to put on very rapidly, particularly in the pistons, the rings, the bores, and the bearings. Either the compressor has vastly insufficient lubrication OR (and more commonly) liquid freon is becoming into the compressor on the suction line. This behavior should be stopped. Consider the expansion valve and at the reversing valve (for any heat pump).
Often an old system experiences enough mechanical wear internally that it is “worn in” and needs more torque to begin from the system load than can be delivered. This technique will sound much like one having a locked bearing; the compressor will buzz loudly for a few seconds then the thermal limiter will kill it. Occasionally, this system begins right up in the event you whack the compressor having a rubber mallet though it may be buzzing. This type of system is an excellent candidate for a hard-start kit. This kit stores energy and, if the compressor is told to begin, dumps extra current in to the compressor to get a second roughly. This overloads the compressor, but gives additional torque for a limited time and is often enough to help make that compressor run again. I have had hard-start kits produce an added 8 or 9 years in some old units that otherwise I might 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 if the symptoms are as described.