Air conditioner compressors generally fail due to one particular of two circumstances: time and hours of operation (put on out), or abuse. There are some failures that can happen elsewhere in the method that will result in a compressor failure, but these are significantly less typical unless the method has been substantially abused.
Normally abuse is a outcome of extended operating with improper freon charge, or as a consequence of improper service along the way. This improper service can incorporate overcharging, undercharging, installing the incorrect starter capacitor as a replacement, removing (rather than repairing/replacing) the thermal limiter, insufficient oil, mixing incompatible oil forms, or incorrect oil, installing the compressor on a method that had a key burnout devoid of taking right actions to eliminate the acid from the method, installing the incorrect compressor (also little) for the method, or installing a new compressor on a method that had some other failure that was by no means diagnosed.
The compressor can fail in only a handful of various approaches. It can fail open, fail shorted, knowledge a bearing failure, or a piston failure (throw a rod), or knowledge a valve failure. That is fairly a great deal the whole list.
When a compressor fails open, a wire inside the compressor breaks. This is unserviceable and the symptom is that the compressor does not run, although it may perhaps hum. If the compressor fails open, and following the actions right here does not repair it, then the method may perhaps be a great candidate for a new compressor. This failure causes no additional failures and will not harm the rest of the method if the rest of the method is not decrepit then it would be price powerful to just place a new compressor in.
Testing for a failed open compressor is straightforward. Pop the electrical cover for the compressor off, and eliminate the wires and the thermal limiter. Making use of an ohmmeter, measure the impedance from one particular terminal to a different across all 3 terminals of the compressor. Also measure the impedance to the case of the compressor for all 3 terminals.
You ought to study low impedance values for all terminal to terminal connections (a couple of hundred ohms or significantly less) and you ought to have a higher impedance (numerous kilo-ohms or higher) for all terminals to the case (which is ground). If any of the terminal to terminal connections is a really higher impedance, you have a failed open compressor. In really uncommon instances, a failed open compressor may perhaps show a low impedance to ground from one particular terminal (which will be one particular of the terminals related with the failed open). In this case, the broken wire has moved and is contacting the case. This situation – which is pretty uncommon but not not possible – could result in a breaker to trip and could outcome in a misdiagnosis of failed brief. Be cautious right here do an acid test of the contents of the lines prior to deciding how to proceed with repair.
When a compressor fails brief, what occurs is that insulation on the wires has worn off or burned off or broken inside the compressor. This makes it possible for a wire on a motor winding to touch a thing it ought to not touch – most frequently itself a turn or two additional along on the motor winding. This benefits in a “shorted winding” which will cease the compressor straight away and result in it to heat up and burn internally.
Negative bearings can result in a failed brief. Either the rotor wobbles sufficient to make contact with the stator, resulting in insulation harm that shorts the rotor either to ground or to the stator, or finish bearing put on can enable the stator to shift down more than time till it starts to rub against the stator ends or the housing.
Normally when one particular of these shorts happen, it is not straight away a challenging brief – which means that initially the make contact with is intermittent and comes and goes. Just about every time the brief happens, the compressor torque drops sharply, the compressor may perhaps shudder a bit visibly as a outcome, and this shudder shakes the winding sufficient to separate the brief. Even though the brief is in spot, the existing by way of the shorted winding shoots up and a lot of heat is developed. Also, generally the brief will blow some sparks – which produces acid inside the air conditioner method by decomposing the freon into a mixture of hydrochloric and hydrofluoric acid.
More than time (possibly a couple of weeks, generally significantly less) the shuddering and the sparking and the heat and the acid result in insulation to fail swiftly on the winding. Eventually, the winding loses sufficient insulation that the inside of the compressor is actually burning. This will only go on for a couple of minutes but in that time the compressor destroys itself and fills the method with acid. Then the compressor stops. It may perhaps at that time melt a wire loose and brief to the housing (which can trip your residence principal breaker) or it may perhaps not. If the initial result in of the failure was undesirable bearings causing the rotor to rub, then generally when the factor ultimately dies it will be shorted to the housing.
If it shorts to the housing, it will blow fuses and/or breakers and your ohmmeter will show a really low impedance from one particular or extra windings to ground. If it does not brief to the housing, then it will just cease. You nevertheless establish the sort of failure working with an ohmmeter.
You can't straight diagnose a failed brief with an ohmmeter unless it shorts to the housing – a shorted winding will not show up with an ohmmeter although it would with an inductance meter (but who has one particular of these?) Alternatively, you have to infer the failed brief. You do this by establishing the the ohmmeter offers regular readings, the starter capacitor is great, energy is arriving at the compressor, AND an acid test of the freon shows acid present.
With a failed brief, just give up. Transform all the things, such as the lines if attainable. It is not worth fixing it is complete of acid and as a result is all junk. Additional, a failed brief could have been initially induced by some other failure in the method that triggered a compressor overload by replacing the complete method you also will get rid of that prospective other dilemma.
Significantly less frequently, a compressor will have a bearing failure, piston failure or a valve failure. These mechanical failures generally just signal put on out but could signal abuse (low lubricant levels, thermal limiter removed so compressor overheats, chronic low freon situation due to un-repaired leaks). Much more hardly ever, they can signal a different failure in the method such as a reversing valve dilemma or an expansion valve dilemma that winds up letting liquid freon get into the suction side of the compressor.
If a bearing fails, generally you will know for the reason that the compressor will sound like a motor with a undesirable 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 will wind up with a failed brief.
If the compressor locks up mechanically and fails to run, you will know for the reason that it will buzz really loudly for a couple of seconds and may perhaps shudder (just like any stalled motor) till the thermal limiter cuts it off. When you do your electrical checks, you will obtain no proof of failed open or failed brief. The acid test will show no acid. In this case, you may well attempt a challenging-begin kit but if the compressor has failed mechanically the challenging-begin kit will not get the compressor to begin. In this case, replacing the compressor is a great program so lengthy as the rest of the method is not decrepit. Right after replacing the compressor, you need to very carefully analyze the overall performance of the whole method to identify whether or not the compressor dilemma was induced by a thing else.
Hardly ever, the compressor will knowledge a valve failure. In this case, it will either sit there and seem to run happily but will pump no fluid (valve will not close), or it will lock up due to an inability to move the fluid out of the compression chamber (valve will not open). If it is operating happily, then after you have established that there is certainly lots of freon in the method, but absolutely nothing is moving, then you have no option but to modify the compressor. Once again, a method with a compressor that has had a valve failure is a great candidate for a new compressor.
Now, if the compressor is mechanically locked up it could be for the reason that of a couple of issues. If the compressor is on a heat pump, make certain the reversing valve is not stuck half way. Also make certain the expansion valve is operating if it is blocked it can lock the compressor. Also make certain the filter is not clogged. I after saw a method that had a locked compressor due to liquid lock. Some idiot had “serviced” the method by adding freon, and adding freon, and adding freon till the factor was absolutely complete of liquid. Trust me that does not function.
Must diagnosis show a clogged filter, then this ought to be taken as constructive proof of some failure in the method OTHER than a compressor failure. Commonly, it will be metal fragments out of the compressor that clogs the filter. This can only take place if a thing is causing the compressor to put on really swiftly, especially in the pistons, the rings, the bores, and the bearings. Either the compressor has vastly insufficient lubrication OR (and extra frequently) liquid freon is acquiring into the compressor on the suction line. This behavior need to be stopped. Appear at the expansion valve and at the reversing valve (for a heat pump).
Usually an old method experiences sufficient mechanical put on internally that it is “worn in” and wants extra torque to begin against the method load than can be delivered. This method will sound just like one particular with a locked bearing the compressor will buzz loudly for a couple of seconds then the thermal limiter will kill it. Sometimes, this method will begin appropriate up if you whack the compressor with a rubber mallet although it is buzzing. Such a method is a great candidate for a challenging-begin kit. This kit shops power and, when the compressor is told to begin, dumps added existing into the compressor for a second or so. This overloads the compressor, but offers some added torque for a brief time and is generally sufficient to make that compressor run once more. I have had challenging-begin kits give me an added eight or 9 years in some old units that otherwise I would have been replacing. Conversely, I have had them give only a couple of months. It is your contact, but thinking of how low-priced a challenging-begin kit is, it is worth attempting when the symptoms are as described.
And this, in a nutshell, is what can take place to an air conditioner compressor and what you can do about it.