AC-Stuck Rings

Hi durtieduck,

The problem you are experiencing is not that uncommon especially amongst hermetic compressors (the totally sealed compressors that are fitted inside most aircon units and fridges - sometimes refered to as 'Dome' compressors).

There are a couple of reasons for this problem but the most common suspected cause is that a small piece of dirt may have lodged in the compressor. Dirt can end up in the refrigerant circuit from a number of causes - dirty charging, poor practice when repairing or replacing components and also during manufacture

You did not give any further information except to say it would not run and maybe the rings were seized. You also mentioned that it was a 110v unit. I have no idea of your technical capabilities but if you are confident and experienced enough (if not please seek professional assistance) then please carry out the following tests :-

- have you confirmed power is getting to the compressor terminals i.e. did you hear any attempt to start or was there any vibration. I ask this because it is also possible that the thermostat may be defective. It would be better if you were checking the current (amps) being drawn with a clamp-on ampmeter (tong tester) when you attempted a start. A stuck compressor would normally draw high amps based on the fact that it is basically in a locked rotor condition.

- I have a fairly easy method of testing whether the power is getting to the compressor (No! I don't use my finger!!!) :- I disconnect the wires from the compressor (noting exactly which terminals they were connected to) and then connect a test lamp (lead light) first between the common and run wires and then if the light comes on then do the same test between the common and start wires. If the lamp comes on for both tests then your compressor would need replacement but if not, then you have a power problem and need to trace back for faulty thermostat or disconnected (broken) wiring within the unit.

Please note - switch OFF and disconnect the power while making these connections and ensure that the disconnected wires are not touching each other or the unit frame!

- have you tested the capacitor or replaced it with one of the same rating (voltage and capacitance) Do NOT go bigger or smaller! Although a lot of meters can measure capacitance I would normally only use this as a guide and prefer replacement. I know there are quite a few repair technicians that believe that installing a capacitor with a higher rating solves the problem but by doing this you alter the characteristics of the motor and normally end up with other problems although these may not be immediately apparent. The capacitor on a single phase motor is in circuit to place the start winding out of phase with the run winding. This is what enables the single phase motor to start and the angle that the start winding is out of phase is determined by the size of rating of the capacitor. This rating is determined by the motor manufacturer and is part of the design parameters for that particular motor. It is true though that within the refrigeration compressor industry you will find that a lot of the manufacturers tend to standardise on the ratings of the capacitors using between 20 & 35 mfd capacitors but the Golden Rule applies here - when replacing components in a system use identical components at all times. The guys that designed that system are normally a lot cleverer than us and have done extensive R & D.

Note that 3 phase motors do not require a starting capacitor.

- have you checked that the windings of the compressor are ok? Do this with the power switched OFF and the plug removed!There are three terminals and they are normally marked either on the cover or adjacent to the terminals :- C = Common, R = Run winding & S = Start winding. Measure the resistance (ohms) of the two windings to confirm that you don't have an open circuit. i.e. C to R =?, C to S = ? & R to S should equal the sum of the first two windings ohms.

- releasing a stuck compressor is a fairly simple exercise and most fridge mechs use one of the diagnostic compressor testers which have a function to do this but it is possible to do this by just swapping over the connections of the start (S) and run (R) windings and then applying power for a very short time : Do NOT exceed one (1) second! Also do NOT exceed three attempts!

- lastly you can read up on this by downloading "Modern Refrigeration and Air Conditioning' from http://www.firstload.com/?uniq=6784f8a9a81df410&log=47515&fn=modern+refrigeration+and+air... and looking up releasing a stuck compressor.

I hope the above is of assistance to you in resolving this problem but would seriously caution you that if you are not experienced enough to carry out these tests then rather seek professional advice - it's a lot safer!

Regards,

Keith