Air conditioner compressors usually fail because of one of two conditions: time and hours of operation (wear out or abuse. There are some failures that can occur elsewhere in the system that can cause a compressor failure, however 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 can include overcharging, undercharging, installing the wrong starter capacitor as an alternative, removing (instead of repairing/replacing) the thermal limiter, insufficient oil, mixing incompatible oil types, or wrong oil, installing the compressor on a system who had a major burnout without taking proper steps to remove the acid from the system, installing a bad compressor (too small) for your system, or installing ACcompressor on the system who had various other failure which had been never diagnosed.
The compressor can fail in just a few various 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 really the whole list.
Whenever a compressor fails open, a wire within the compressor breaks. This really is unserviceable and also the symptom would be that the compressor fails to run, even though it may hum. In the event the compressor fails open, and following the steps here fails to correct it, then your system can be a good candidate for any new compressor. This failure causes no further failures and won’t damage the remainder of the system; if the rest of the product is not decrepit then it would be cost effective to just put a brand new compressor in.
Testing for a failed open compressor is simple. Pop the electrical cover for your compressor off, and take off the wires and also the thermal limiter. Using an ohmmeter, appraise the impedance in one terminal to another one across the 3 terminals in the compressor. Also measure the impedance to the case in the compressor for those three terminals.
You should read low impedance values for many terminal to terminal connections (a couple of hundred ohms or less) and you should have a high impedance (several kilo-ohms or greater) for all terminals towards the case (which is ground). If some of the terminal to terminal connections is definitely a high impedance, you have a failed open compressor. In very rare cases, a failed open compressor may show a low impedance to ground in one terminal (which is among the terminals linked to the failed open). In this case, the broken wire has moved and is contacting the case. This condition – that is quite rare but not impossible – might cause a breaker to trip and could result in a misdiagnosis of failed short. Be mindful here; do an acid test from the items in the lines before deciding the best way to proceed with repair.
When a compressor fails short, what happens is the fact insulation on the wires has worn off or burned off or broken within the Bathtub Faucet. This permits a wire over a motor winding to touch something it ought to not touch – most frequently 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 warm 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 even to the stator, or end bearing wear can enable the stator to shift down over time until it begins to rub from the stator ends or the housing.
Usually when one of these shorts occur, it is not immediately a hard short – which means that initially the contact is intermittent and comes and goes. Every time the short occurs, the compressor torque drops sharply, the compressor may shudder somewhat visibly because of this, and also 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 a lot of heat is produced. Also, usually short will blow some sparks – which produces acid inside vqxigq ac unit system by decomposing the freon into a blend of hydrochloric and hydrofluoric acid.
As time passes (possibly a few weeks, usually less) the shuddering and also 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 the within the compressor is burning. This may only carry on for a few minutes but in that point the compressor destroys itself and fills the program with acid. Then your compressor stops. It may at that time melt a wire loose and short for the housing (which may trip your house main breaker) or it might not. When the initial cause of the failure was bad bearings resulting in the rotor to rub, then usually once the thing finally dies it will be shorted for the housing.
If this shorts for the housing, it can blow fuses or breakers as well as your ohmmeter will show a really low impedance from a number of windings to ground. If this will not short to the housing, it will just stop. You will still establish the sort of failure utilizing an ohmmeter.
You can not directly diagnose a failed short with the ohmmeter unless it shorts towards the housing – a shorted winding won’t show up with the ohmmeter although it would with the inductance meter (but who may have one of those particular?) Instead, you need to infer the failed short. You do 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 of the freon shows acid present.
Using a failed short, just quit. Change everything, like the lines if possible. It is far from worth fixing; it is filled with acid and for that reason 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 whole system you also will eliminate that potential other problem.
Less commonly, a compressor will have a bearing failure, piston failure or perhaps 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 could signal another failure inside 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 be aware since the compressor will sound like a motor with a bad bearing, or it can lock up and refuse to perform. Inside the worst case, the rotor will wobble, the windings will rub on the stator, and you will find yourself using a failed short.
In the event the compressor locks up mechanically and fails to run, you will know 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 might consider using a hard-start kit but if the compressor has failed mechanically the difficult-start kit won’t have the compressor to start. In this case, replacing the compressor is a good plan so long as the remainder of the method is not decrepit. After replacing the compressor, you must carefully analyze the performance of the entire system to determine whether the compressor problem was induced by something different.
Rarely, the compressor will experience a valve failure. In cases like this, it is going to either sit there and appear to run happily but will pump no fluid (valve won’t close), or it will lock up because of an inability to move the fluid out from the compression chamber (valve won’t open). Should it be running happily, then once you have established there is indeed a lot of freon in the system, but nothing is moving, then you do not have choice but to change the compressor. Again, a process with auto which includes had a valve failure is a good candidate for a new compressor.
Now, in the event the compressor is mechanically locked up it can be because of a couple of things. In the event the compressor is on a heat pump, make sure the reversing valve is not really stuck half way. Also make sure the expansion valve is working; should it be blocked it can lock the compressor. Also make sure the filter will not be clogged. I once saw a process which 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 until the thing was completely packed with liquid. Believe me; that will not work.
Should diagnosis show a clogged filter, then this should be taken as positive evidence of some failure within the system Besides a compressor failure. Typically, it will be metal fragments from the compressor that clogs the filter. This may only happen if something is causing 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 a lot more commonly) liquid freon is getting in to the compressor on the suction line. This behavior has to 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 must be “worn in” and needs more torque to begin up against the system load than could be delivered. This method will sound just like one with a locked bearing; the compressor will buzz loudly for a couple seconds then this thermal limiter will kill it. Occasionally, this system will start right up if you whack the compressor with a rubber mallet even though it is buzzing. Such a system is a great candidate for a hard-start kit. This kit stores energy and, when the compressor is told to begin, dumps extra current into the compressor for a second roughly. This overloads the compressor, but gives some extra torque for any short period of time and it is often enough to help make that compressor run again. I have had hard-start kits deliver an added 8 or 9 years in a few old units that otherwise I might have been replacing. Conversely, We have had them give only a few months. It really is your call, but considering how cheap a tough-start kit is, it really is worth trying when the symptoms are as described.