mightypeesh Posted October 2, 2020 Share Posted October 2, 2020 Hi chaps. My old faithful compressor has stopped working - when you switch on it just hums for a second then switches off again. Having researched I am pretty sure it is the start capacitor that needs replacing. My questions are, where do I buy one from and which numbers on the side of it are relevant to getting the correct part for the job as there are quite a few on there to choose from? Also is the resister on there unique to that particular starter or will I need to transfer it to the new one whatever make it is? Please see pics below. Sorry, I cannot get the one of the cap to post the right way up! Thanks for your assistance, cheers, Simon Quote Link to comment Share on other sites More sharing options...
Sparks Posted October 2, 2020 Share Posted October 2, 2020 Hi, The relevant values are 56uF and 250V, So most Motor Start capacitors near this valus will be OK. Something like this :LINK You will have to transfer the resistor from the old one, check it with an ohmeter to make sure it is not open circuit Quote Link to comment Share on other sites More sharing options...
Denis Watkins Posted October 2, 2020 Share Posted October 2, 2020 Too late Sparks beat me to it Edited By Denis Watkins on 02/10/2020 16:32:58 Quote Link to comment Share on other sites More sharing options...
mightypeesh Posted October 2, 2020 Author Share Posted October 2, 2020 Wow, quick off the mark, thank you. I checked the resister and it's not open. I will order one and hopefully that will sort the problem out. Cheers, Simon Quote Link to comment Share on other sites More sharing options...
Brian Sweeting 1 Posted October 2, 2020 Share Posted October 2, 2020 The capacitor is a "run" capacitor and the resistor is there to bleed off the capacitor charge when the motor is switched off. The important number when ordering a new capacitor is the voltage, it can be higher but don't go lower. You should be able to get one from an electrical wholesaler as well as the usual internet sources. Quote Link to comment Share on other sites More sharing options...
Barryorbik Posted October 2, 2020 Share Posted October 2, 2020 The resistor colours appear to indicate its value as 270K Ohms so your meter should read something close to this value (when the resistor is disconnected from the circuit) and its probably rated at 1 Watt, but it is hard to tell the body size from the picture. Barry Quote Link to comment Share on other sites More sharing options...
Sparks Posted October 2, 2020 Share Posted October 2, 2020 I'm not very good with colours, but it looks like red, violet, orange to me. In which case it would be 27k ?? Quote Link to comment Share on other sites More sharing options...
Andy Stephenson Posted October 2, 2020 Share Posted October 2, 2020 It's important that you get a capacitor that is rated at 250V AC. The AC it important as a normal decoupling capacitor is only rated for a small ripple current. It must not be a polarised electrolytic type. Edited By Andy Stephenson on 02/10/2020 21:12:32 Edited By Andy Stephenson on 02/10/2020 21:14:20 Quote Link to comment Share on other sites More sharing options...
Andy Stephenson Posted October 2, 2020 Share Posted October 2, 2020 Sparks, You are right it looks like 27k to me too. Quote Link to comment Share on other sites More sharing options...
Barryorbik Posted October 2, 2020 Share Posted October 2, 2020 Simon, Sorry, just had another look at your photograph and it does look like Orange so it's a x3 multiplier giving a value of 27K. Quote Link to comment Share on other sites More sharing options...
mightypeesh Posted October 3, 2020 Author Share Posted October 3, 2020 Thank you for all your info. I have contacted a company and sent photos for them to confirm I am buying the right part. Cheers to you all, Simon Quote Link to comment Share on other sites More sharing options...
Mike T Posted October 3, 2020 Share Posted October 3, 2020 Posted by Brian Sweeting 1 on 02/10/2020 17:58:41: The capacitor is a "run" capacitor and the resistor is there to bleed off the capacitor charge when the motor is switched off. I have exactly the same problem as the OP - a buzzing sound for a few seconds and then silence. It happened on a previous compressor I owned (same make/model) and swapping out the capacitor with that from a friend's (identical) compressor made no difference... But if the cap is a run cap, shouldn't the motor start and run anyway? Quote Link to comment Share on other sites More sharing options...
Brian Sweeting 1 Posted October 3, 2020 Share Posted October 3, 2020 Posted by Mike T on 03/10/2020 14:17:45: Posted by Brian Sweeting 1 on 02/10/2020 17:58:41: The capacitor is a "run" capacitor and the resistor is there to bleed off the capacitor charge when the motor is switched off. I have exactly the same problem as the OP - a buzzing sound for a few seconds and then silence. It happened on a previous compressor I owned (same make/model) and swapping out the capacitor with that from a friend's (identical) compressor made no difference... But if the cap is a run cap, shouldn't the motor start and run anyway? Sorry I can't answer that as secondly have the OPs report on that particular capacitor. What else is in circuit is unknown. On a refrigeration compressor there is often a Klixon type overload which cuts the power supply on overload startups. The compressor could be seized although electrically sound. Quote Link to comment Share on other sites More sharing options...
Mike T Posted October 3, 2020 Share Posted October 3, 2020 Posted by Brian Sweeting 1 on 03/10/2020 14:41:06:. The compressor could be seized although electrically sound. That's my fear. When the old one failed, I took the lid off it but could not turn the motor by hand . I sincerely hope I'm wrong and that a new cap will sort the OP's problem! It's all a bit annoying as my compressor was rarely used for anything other than occasional redistribution of dust around the workshop - yet the same type of compressor works for years in the fridge... Quote Link to comment Share on other sites More sharing options...
Brian Sweeting 1 Posted October 3, 2020 Share Posted October 3, 2020 Mike T, when the compressor is working at it's design role, pumping refrigerant, then the returning refrigerant gas provides cooling to the motor. Also, any oil that is pumped out of the compressor as mist was returned to the compressor sump with the circulating refrigerant. A refrigeration compressor is also normally limited to about six starts per hour to prevent motor overheating. Quote Link to comment Share on other sites More sharing options...
Mike T Posted October 5, 2020 Share Posted October 5, 2020 Posted by mightypeesh on 03/10/2020 11:07:28: Thank you for all your info. I have contacted a company and sent photos for them to confirm I am buying the right part. Cheers to you all, Simon Please keep us posted, Simon. Which Company did you contact? @Brian - thanks for the info. Although my compressor has had any easy time with me, it may have been hammered in its previous life - something to do with security tagging in a department store! Quote Link to comment Share on other sites More sharing options...
Former Member Posted October 5, 2020 Share Posted October 5, 2020 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted October 5, 2020 Share Posted October 5, 2020 I had a similar situation, and was about to resort to buying spares, when it mysteriously started working again. That was two years ago. With some old disk drives (I am talking the ones as big as dishwashers, I know I am getting old) they had an inertia switch that altered the windings, once it started spinning it switched over. Those flaming microswitches caused so much grief and more than a few motor changes. The only thing I could think of on my compressor was a similar switch in the motor that I may have disturbed with all the dismantling.... My compressor is a much larger unit than yours Simon so may have no bearing, I hate to suggest it but have you given it a percussive tap? Cheers Danny Quote Link to comment Share on other sites More sharing options...
Mike T Posted October 7, 2020 Share Posted October 7, 2020 Well this thread prompted me to unearth the disassembled remains of my old compressor, for some comparative testing. Long story short, I swapped over the start capacitor and the newer machine kicked into life! (The older is definitely dead, due to a seized motor that seems impossible to extract from its 'chest' for disassembly). Given the OPs compressor exhibited the same fault as mine, I hope it just requires a new cap to fix it! FWIW, I found this very useful: **LINK** Quote Link to comment Share on other sites More sharing options...
Mike T Posted October 15, 2020 Share Posted October 15, 2020 @Simon (OP) - did you get it fixed? Quote Link to comment Share on other sites More sharing options...
Alex Ferguson 2 Posted October 15, 2020 Share Posted October 15, 2020 Posted by Mike T on 03/10/2020 14:17:45: Posted by Brian Sweeting 1 on 02/10/2020 17:58:41: The capacitor is a "run" capacitor and the resistor is there to bleed off the capacitor charge when the motor is switched off. But if the cap is a run cap, shouldn't the motor start and run anyway? There should be two windings and they are mechanically spaced. To make the motor work the windings get their voltages out of phase and the capacitor does that. It is driven by AC voltage so the voltage is increasing in a sine wave shape followed by a reversal of voltage. Put simply, one winding has voltage to it to "move" the armature part way round and then the next winding gets the phase shifted voltage (power) to move the armature on again. Then the voltage reverses and the rest of the rotation carries on. For lots of power and no capacitors, three phase power does it, each of three windings getting their voltage in sequential steps. Quote Link to comment Share on other sites More sharing options...
mightypeesh Posted November 24, 2020 Author Share Posted November 24, 2020 Hi Chaps, sorry been busy with work and have only just got around to having another look at my compressor - glad it sorted yours out though Mike! Unfortunately mine is still no go, changed the cap but it still just hums and sits there looking at me! I will have a look at the video you posted Mike and see if I can trouble shoot the other components, though I am not very electronically minded. I have had a look inside to see if I can turn the motor manually but it is completely sealed once you get past the outer case and has no way that I can see to get to any revolving parts to find out if it is seized. Thank you for all of your comments and suggestions I will work though them. If it does not work I may be giving Father Christmas a nudge to see if he can come up with the goods! Cheers, Simon Quote Link to comment Share on other sites More sharing options...
mightypeesh Posted November 24, 2020 Author Share Posted November 24, 2020 Looking at that video I have tested the start relay using a meter and not getting any reading regardless of which way up the relay is when tested across the connections. I have tried with continuity setting and with ohm's (200) and there is no response. Does this sound like it is the culprit? If so which are the important numbers on the casing to specify a new part? Many thanks, Cheers, Simon Quote Link to comment Share on other sites More sharing options...
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