Air conditioner compressors usually fail as a result of one of two conditions: time and hours of operation (wear out or abuse. There are several failures that can occur elsewhere in the system that will cause a compressor failure, however these are less frequent 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 can include overcharging, undercharging, installing a bad starter capacitor as an alternative, removing (rather than repairing/replacing) the thermal limiter, insufficient oil, mixing incompatible oil types, or wrong oil, installing the compressor over a system who had an important burnout without taking proper steps to remove the acid through the system, installing the incorrect compressor (too small) for that system, or installing ACcompressor on a system which had a few other failure which was never diagnosed.
The compressor can fail within just a few different ways. 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 whole list.
When a compressor fails open, a wire in the compressor breaks. This really is unserviceable as well as the symptom would be that the compressor will not run, even though it may hum. If the compressor fails open, and after the steps here fails to remedy it, then the 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 all of those other product is not decrepit then it might be affordable to simply put a whole new compressor in.
Testing for a failed open compressor is easy. Pop the electrical cover for your compressor off, and take away the wires and also the thermal limiter. Utilizing an ohmmeter, appraise the impedance from a single terminal to another across all three terminals of the compressor. Also appraise the impedance for the case from the compressor for many three terminals.
You need to 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 many terminals to the case (which can be ground). If any of the terminal to terminal connections is a very high impedance, there is a failed open compressor. In very rare cases, a failed open compressor may show a small impedance to ground in one terminal (which is among the terminals related to the failed open). In cases like this, the broken wire has moved and is contacting the situation. This problem – that is quite rare however, not impossible – might cause a breaker to trip and can result in a misdiagnosis of failed short. Be mindful here; do an acid test from the valuables in the lines before deciding how you can proceed with repair.
When a compressor fails short, what happens is that insulation on the wires has worn off or burned off or broken within the Showerhead. This permits a wire on a motor winding to touch something it must not touch – most commonly itself a turn or two further along on the motor winding. This results in a “shorted winding” that will stop the compressor immediately and cause it to warm up and burn internally.
Bad bearings may cause a failed short. Either the rotor wobbles enough to contact 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 up against the stator ends or perhaps the housing.
Usually when one of those shorts occur, it is far from immediately a tough 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 somewhat visibly as a result, and this shudder shakes the winding enough to separate the short. While the short is at place, the existing with the shorted winding shoots up and plenty 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 couple of weeks, usually less) the shuddering and the sparking as well as the heat and also the acid cause insulation to fail rapidly on the winding. Ultimately, the winding loses enough insulation the inside the compressor is literally burning. This will only go on for a couple of minutes however in that point the compressor destroys itself and fills the system with acid. Then your compressor stops. It might during that time melt a wire loose and short for the housing (which may trip your house main breaker) or it may possibly not. In the event the initial reason for the failure was bad bearings causing the rotor to rub, then usually once the thing finally dies it will be shorted towards the housing.
When it shorts for the housing, it can blow fuses and/or breakers along with your ohmmeter shows a really low impedance from one or more windings to ground. If this fails to short to the housing, this will just stop. You still establish the type of failure utilizing an ohmmeter.
You are unable to directly diagnose a failed short with the ohmmeter unless it shorts towards the housing – a shorted winding won’t turn up having an ohmmeter although 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 good, power is coming to the compressor, As well as an acid test of the freon shows acid present.
Having a failed short, just give up. Change everything, including the lines if at all possible. It is not worth fixing; it is loaded with acid and thus is actually all junk. Further, a failed short could have been initially induced by various 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 even a valve failure. These mechanical failures usually just signal wear out 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 can signal another failure inside the system for instance a reversing valve problem or even an expansion valve problem that winds up letting liquid freon get into the suction side from the compressor.
When a bearing fails, usually you will know as the compressor will seem to be a motor having a bad bearing, or it is going to lock up and refuse to run. Within the worst, 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 operate, you will know since it will buzz very loudly for a few seconds and may shudder (as with every stalled motor) till the thermal limiter cuts it away. Whenever you do your electrical checks, you will find no proof of failed open or failed short. The acid test shows no acid. In this case, 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 out. In this instance, replacing the compressor is a great plan as long as the rest of the method 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 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 as a result of an lack of ability to move the fluid out from the compression chamber (valve won’t open). When it is running happily, then once you have established that there is actually a lot of freon in the system, but nothing is moving, then you do not have choice but to modify the compressor. Again, a system with auto which has had a valve failure is an excellent candidate to get a new compressor.
Now, if the compressor is mechanically locked up it may be because of few things. In the event the compressor is on the heat pump, make sure the reversing valve will not be stuck half way. Also make sure the expansion valve is working; should it be blocked it can lock the compressor. Also ensure the filter will not be clogged. One time i saw a system that had a locked compressor due to liquid lock. Some idiot had “serviced” the system by adding freon, and adding freon, and adding freon till the thing was completely filled with liquid. Trust me; that does not work.
Should diagnosis show a clogged filter, then this needs to be taken as positive evidence of some failure in the system OTHER than a compressor failure. Typically, it will be metal fragments out of 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 to the compressor on the suction line. This behavior has to be stopped. Glance at the expansion valve as well as at the reversing valve (to get a heat pump).
Often an old system experiences enough mechanical wear internally that it is “worn in” and needs more torque to start up against 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 couple seconds then your thermal limiter will kill it. Occasionally, this method will start right up in the event you whack the compressor with a rubber mallet even though it is buzzing. This type of system is a great candidate for any 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 approximately. This overloads the compressor, but gives a little extra torque for any short time and it is often enough to make that compressor run again. I have had hard-start kits produce an extra 8 or 9 years in certain old units that otherwise I might have been replacing. Conversely, I have had them give only some months. It really is your call, but considering how cheap a tough-start kit is, it is actually truly worth trying once the symptoms are as described.