Air conditioner compressors usually fail due to 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 will result in a compressor failure, however, these are less common unless the system has been substantially abused.
Usually abuse is a result of extended running with improper freon charge, or caused by improper service as you go along. This improper service might include overcharging, undercharging, installing the incorrect 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 a system who had a major burnout without taking proper steps to get rid of the acid from the system, installing the wrong compressor (too small) for the system, or installing A/C Compressor on a system who had some other failure which was never diagnosed.
The compressor can fail in only a number of different methods. It can 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 entire list.
Whenever a compressor fails open, a wire in the compressor breaks. This is unserviceable as well as the symptom is that the compressor does not run, even though it may hum. In the event the compressor fails open, and following the steps here does not remedy it, then your system might be a good candidate for any new compressor. This failure causes no further failures and won’t damage all of those other system; if all of those other method is not decrepit then it would be cost effective to merely put a new compressor in.
Testing for a failed open compressor is easy. Pop the electrical cover for your compressor off, and remove the wires and the thermal limiter. Utilizing an ohmmeter, measure the impedance from a single terminal to another across all three terminals from the compressor. Also measure the impedance towards the case in the compressor for all three terminals.
You need to read low impedance values for those terminal to terminal connections (several hundred ohms or less) and you ought to have a high impedance (several kilo-ohms or greater) for those terminals for the case (that is ground). If any of the terminal to terminal connections is an extremely high impedance, there is a failed open compressor. In rare cases, a failed open compressor may show a small impedance to ground in one terminal (that will be one of many terminals linked to the failed open). In this case, the broken wire has moved and is also contacting the situation. This condition – which can be quite rare although not impossible – might lead to a breaker to trip and could result in a misdiagnosis of failed short. Be careful here; do an acid test of the contents of the lines before deciding how you can proceed with repair.
When a compressor fails short, what goes on is the fact insulation on the wires has worn off or burned off or broken in the shower faucet. This allows a wire on the motor winding to touch something it should 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 heat up and burn internally.
Bad bearings could cause a failed short. Either the rotor wobbles enough to contact the stator, resulting in insulation damage that shorts the rotor either to ground or even to 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 the housing.
Usually when one of those shorts occur, it is far from immediately a hard short – which means that initially the contact is intermittent and comes and goes. Each and every time the short occurs, the compressor torque drops sharply, the compressor may shudder somewhat visibly consequently, and this shudder shakes the winding enough to separate the short. While the short is at place, the present with the shorted winding shoots up and a lot of heat is produced. Also, normally the short will blow some sparks – which produces acid inside vqxigq air conditioner system by decomposing the freon into a mixture of hydrochloric and hydrofluoric acid.
Over time (possibly a couple of weeks, usually less) the shuddering and the sparking as well as the heat and the acid cause insulation to fail rapidly on the winding. Ultimately, the winding loses enough insulation the within the compressor is literally burning. This can only carry on for a few minutes however in that time the compressor destroys itself and fills the device with acid. Then your compressor stops. It could during those times melt a wire loose and short towards the housing (which could trip your house main breaker) or it might not. If the initial reason for the failure was bad bearings creating the rotor to rub, then usually if the thing finally dies it will probably be shorted to the housing.
If this shorts towards the housing, it can blow fuses and/or breakers as well as your ohmmeter shows a very low impedance from several windings to ground. If this fails to short towards the housing, then it will just stop. You still establish the type of failure utilizing an ohmmeter.
You are unable to directly diagnose a failed short having an ohmmeter unless it shorts for the housing – a shorted winding won’t show up having an ohmmeter though it would with the inductance meter (but who has among those?) Instead, you need to infer the failed short. You do this by establishing the the ohmmeter gives normal readings, the starter capacitor is nice, power is arriving at the compressor, Plus an acid test in the freon shows acid present.
Having a failed short, just quit. Change everything, such as the lines if at all possible. It is really not worth fixing; it is loaded with acid and thus is perhaps all junk. Further, a failed short might have been initially induced by a few other failure within the system that caused a compressor overload; by replacing the whole system you also will remove that potential other problem.
Less commonly, a compressor may have a bearing failure, piston failure or perhaps a valve failure. These mechanical failures usually just signal degrade 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 could signal another failure inside the system like a reversing valve problem or perhaps an expansion valve problem that winds up letting liquid freon go into the suction side of the compressor.
When a bearing fails, usually you will understand because the compressor will seem to be a motor having a bad bearing, or it will lock up and refuse to operate. Inside the worst case, the rotor will wobble, the windings will rub on the stator, and you will end up with a failed short.
If the compressor locks up mechanically and fails to operate, you will know as it will buzz very loudly for a couple seconds and could shudder (as with any stalled motor) till the thermal limiter cuts it away. Whenever you do your electrical checks, you will find no evidence of failed open or failed short. The acid test shows no acid. In cases like this, you could consider using a hard-start kit but if the compressor has failed mechanically the difficult-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 must carefully analyze the performance from the entire system to determine whether or not the compressor problem was induced by something else.
Rarely, the compressor are experiencing a valve failure. In this instance, it can either sit there and seem to run happily and can pump no fluid (valve won’t close), or it can lock up due to an lack of ability to move the fluid out of the compression chamber (valve won’t open). Should it be running happily, then when you have established that there is actually a lot of freon in the system, but there is nothing moving, then you have no choice but to change the compressor. Again, a process with car which includes had a valve failure is a great candidate to get a new compressor.
Now, in the event the compressor is mechanically locked up it may be because of couple of things. In the event the compressor is on the heat pump, ensure the reversing valve is not stuck half way. Also ensure that the expansion valve is working; should it be blocked it may lock the compressor. Also ensure the filter is not really clogged. I once saw a process who had a locked compressor due to liquid lock. Some idiot had “serviced” the system with the help 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 ought to be taken as positive proof some failure inside the system Apart from a compressor failure. Typically, it will probably be metal fragments from the compressor that clogs the filter. This can only happen if something causes the compressor to use very rapidly, particularly in the pistons, the rings, the bores, and the bearings. Either the compressor has vastly insufficient lubrication OR (and much more commonly) liquid freon is becoming in to the compressor on the suction line. This behavior has to be stopped. Consider 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 requires more torque to start 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 few seconds then the thermal limiter will kill it. Occasionally, this method will start right up in the event you whack the compressor having a rubber mallet though it may be buzzing. This kind of system is a great candidate for any hard-start kit. This kit stores energy and, if the compressor is told to begin, dumps extra current in to the compressor for a second approximately. This overloads the compressor, but gives some extra torque for any short time and it is often enough to make that compressor run again. I actually have had hard-start kits produce an extra 8 or 9 years in a few old units that otherwise I would have been replacing. Conversely, We have had them give just a few months. It is actually your call, but considering how cheap a tough-start kit is, it is worth trying if the symptoms are as described.