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 within the system that can result in a compressor failure, but these are more uncommon unless the system has been substantially abused.
Usually abuse is a result of 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 (instead of repairing/replacing) the thermal limiter, insufficient oil, mixing incompatible oil types, or wrong oil, installing the compressor on the system which had a significant burnout without taking proper steps to remove the acid from your system, installing the incorrect compressor (too small) for the system, or installing ACcompressor on the system which had various other failure that was never diagnosed.
The compressor can fail within just a number of different methods. It could fail open, fail shorted, experience a bearing failure, or a piston failure (throw a rod), or experience a valve failure. That is really the complete list.
When a compressor fails open, a wire within the compressor breaks. This really is unserviceable as well as the symptom would be that the compressor fails to run, though it may hum. When the compressor fails open, and pursuing the steps here does not remedy it, then this system might be a good candidate for a new compressor. This failure causes no further failures and won’t damage the remainder of the system; if all of those other product is not decrepit then it will be cost effective to merely put a brand new compressor in.
Testing for any failed open compressor is simple. Pop the electrical cover for your compressor off, and remove the wires and the thermal limiter. Utilizing an ohmmeter, appraise the impedance in one terminal to another across all 3 terminals from the compressor. Also look at the impedance towards 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 need to have a superior impedance (several kilo-ohms or greater) for many terminals for the case (which is ground). If some of the terminal to terminal connections is a very high impedance, you do have a failed open compressor. In unusual cases, a failed open compressor may show a low impedance to ground from a single terminal (which will be among the terminals linked to the failed open). In this instance, the broken wire has moved and is contacting the situation. This disorder – that is quite rare however, not impossible – could cause a breaker to trip and may result in a misdiagnosis of failed short. Be cautious here; do an acid test in the contents of the lines before deciding the best way to proceed with repair.
Each time a compressor fails short, what happens is that insulation on the wires has worn off or burned off or broken inside the shower faucet. This allows a wire over 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” that can stop the compressor immediately and make it 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 over time until it starts to rub against the stator ends or 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. Every time the short occurs, the compressor torque drops sharply, the compressor may shudder a bit visibly because of this, which shudder shakes the winding enough to separate the short. Whilst the short is in place, the present from the shorted winding shoots up and lots of heat is produced. Also, normally 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.
With time (possibly a few 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 the within the compressor is literally burning. This can only carry on for a couple of minutes but in that period the compressor destroys itself and fills the device with acid. Then the compressor stops. It may at that time melt a wire loose and short to the housing (which could trip your home main breaker) or it may not. If the initial cause of the failure was bad bearings causing the rotor to rub, then usually once the thing finally dies it will likely be shorted for the housing.
If this shorts to the housing, it is going to blow fuses and/or breakers as well as your ohmmeter will demonstrate a very low impedance from several windings to ground. If this does not short to the housing, this will just stop. You will still establish the type of failure utilizing an ohmmeter.
You can not directly diagnose a failed short having an ohmmeter unless it shorts to the housing – a shorted winding won’t show up having an ohmmeter although it would having an inductance meter (but who has one of those particular?) Instead, you must 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, Plus an acid test from the freon shows acid present.
Using a failed short, just quit. Change everything, such as the lines when possible. It is far from worth fixing; it is full of acid and thus is perhaps 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 will have a bearing failure, piston failure or a valve failure. These mechanical failures usually just signal degrade 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 are able to signal another failure in the system like a reversing valve problem or an expansion valve problem that winds up letting liquid freon enter into the suction side from the compressor.
When a bearing fails, usually you will understand since the compressor will seem to be a motor using a bad bearing, or it is going to lock up and refuse to operate. Within the worst, the rotor will wobble, the windings will rub on the stator, and you may wind up having a failed short.
In the event the compressor locks up mechanically and fails to run, you will be aware since 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. Whenever you do your electrical checks, you can find no proof of failed open or failed short. The acid test will demonstrate no acid. In this instance, you could try a hard-start kit however 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 a good plan so long as all of those other system is not decrepit. After replacing the compressor, you have to carefully analyze the performance from the entire system to find out if 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 but will pump no fluid (valve won’t close), or it will lock up due to an inability to move the fluid from the compression chamber (valve won’t open). If it is running happily, then when you have established that there is definitely lots of freon inside the system, but nothing is moving, then you definitely do not have choice but to alter the compressor. Again, a system with car that has experienced a valve failure is a good candidate for any new compressor.
Now, when the compressor is mechanically locked up it could be due to a few things. In the event the compressor is on a heat pump, ensure the reversing valve is not stuck halfway. Also ensure the expansion valve is working; should it be blocked it can lock the compressor. Also ensure that the filter is not really clogged. I remember when i saw a system who had a locked compressor due to liquid lock. Some idiot had “serviced” the device with the addition of freon, and adding freon, and adding freon till the thing was completely full of liquid. Believe me; that does not work.
Should diagnosis show a clogged filter, then this needs to be taken as positive evidence of some failure within the system Besides a compressor failure. Typically, it will probably be metal fragments out from the compressor that clogs the filter. This could only happen if something is bringing about the compressor to wear very rapidly, particularly in the pistons, the rings, the bores, as well as the bearings. Either the compressor has vastly insufficient lubrication OR (and more commonly) liquid freon is getting into the compressor on the suction line. This behavior must be stopped. Look at the expansion valve and also at the reversing valve (to get a heat pump).
Often an old system experiences enough mechanical wear internally that it is “worn in” and desires more torque to begin up against the system load than may be delivered. This method will sound just like one with a locked bearing; the compressor will buzz loudly for a couple of seconds then the thermal limiter will kill it. Occasionally, this system begins right up if you whack the compressor with a rubber mallet even though it is buzzing. This kind of system is a good candidate for a hard-start kit. This kit stores energy and, once the compressor is told to begin, dumps extra current into the compressor for any second or so. This overloads the compressor, but gives some extra torque to get a short time and is also often enough to help make that compressor run again. I actually have had hard-start kits give me an added 8 or 9 years in some old units that otherwise I would have been replacing. Conversely, We have had them give only some months. It is actually your call, but considering how cheap a hard-start kit is, it is actually worth trying if the symptoms are as described.