Members Gary in NJ Posted December 4, 2008 Members Share Posted December 4, 2008 This is completely off topic, but I have found the people in this forum to be very knowledgeable on all things electronic. I have an old Craftsman air compressor. The motor seems to be "tired". Sometimes it starts, and sometimes it doesn't. If it doesn't start, it trips the breaker. If I'm quick enough, I can turn off the switch, rotate the belt an inch, and it starts. But, it does sound a bit "tired" to me. I have no way to confirm this, but it sounds as though it isn't turning quite as fast as it did in the past. Is there a component that I can replace on the motor to bring it back to life? I tied to locate a rebuild kit, to no avail. Any suggestions? Link to comment Share on other sites More sharing options...
Members gspointer Posted December 4, 2008 Members Share Posted December 4, 2008 Starter cap, or it may have starter windings that are switched off centrifugally after the motor starts. Link to comment Share on other sites More sharing options...
Members kevinnem Posted December 4, 2008 Members Share Posted December 4, 2008 comutator, the wire busshings... lots of stuff. some thoughts though.... I have a table saw that explodes from time to time, ... everytime that has happened it has been due to teh belt being to tight. Might this be your issue as well? The belt is too tight, or too loose? I heard you can buy spray stuff to make it more slippery or grabby, that might help the situation a little bit. Is your motor getting enough voltage? ... you aren't running this thing at the end of 600 feet of 18 gauge wire are you? oil --- does your compressor need oil, or is it the oilless type? You can replace the whole motor, lots for sale used I am sure. Link to comment Share on other sites More sharing options...
Members Coaster Posted December 4, 2008 Members Share Posted December 4, 2008 every time i have ever experienced things like this with motors - in the end i got a new motor. the fact that you can move it a little and it starts sounds like a brush/commutator issue but i thought these air compressors usually used inductance motors. i have a belt sander that uses brushes and works fine except the brushes are completely worn down. the sander is 30 years old and i cant find brushes for it so once in a while i have to give it a good thump to get it to start. if your air compressor is an older style with a motor that just hangs out in the open it should be easy to replace it with a similar motor Link to comment Share on other sites More sharing options...
Members Gary in NJ Posted December 5, 2008 Author Members Share Posted December 5, 2008 every time i have ever experienced things like this with motors - in the end i got a new motor.the fact that you can move it a little and it starts sounds like a brush/commutator issue but i thought these air compressors usually used inductance motors.i have a belt sander that uses brushes and works fine except the brushes are completely worn down. the sander is 30 years old and i cant find brushes for it so once in a while i have to give it a good thump to get it to start.if your air compressor is an older style with a motor that just hangs out in the open it should be easy to replace it with a similar motor It's the older style. The starter & run caps are mounted on the outside under covers. I paid $399 for this compressor (new) in 1987. The replacement motor is $350. Seems to me it should be repairable. The unit must have hundreds, if not thousands of hours on it. While I was building my plane it would run for a few hours a day - for 5 years.It may need new brushes. But I attempted to disassemble the unit a few weeks back and it was clear that it would be difficult to do so without knowledge of what I was looking at, or looking for. Link to comment Share on other sites More sharing options...
Members Coaster Posted December 5, 2008 Members Share Posted December 5, 2008 wow. $350 is a lot. i wonder if there are any eletric motor repair shops near you? there was one here that did a great job but a minnesota beautification project tore their shop down. Link to comment Share on other sites More sharing options...
Members gspointer Posted December 5, 2008 Members Share Posted December 5, 2008 I would suspect the starter cap or the start windings/cicuit. Link to comment Share on other sites More sharing options...
Members gspointer Posted December 5, 2008 Members Share Posted December 5, 2008 Oh, I might also look at harbor freight for a cheap substituite. Link to comment Share on other sites More sharing options...
Members W. M. Hellinger Posted December 5, 2008 Members Share Posted December 5, 2008 Is there a component that I can replace on the motor to bring it back to life? I tied to locate a rebuild kit, to no avail. Any suggestions? Have you changed the oil in the compressor? I suggest using real compressor oil if you haven't. I have exactly the same problem with my NAPA air compressor, which looks to me to be identical to a paticular Craftsman air compressor. After much screwing around... including replacing the relief valve, and then installing a manual relief valve and replacing the caps in the motor, and replacing the primary (start-up) low-gear doo-dad assembly in the motor ... I found that the cheeze-ball barely adequate motor was probably engineered to spin-up the compressor at southern climate temperatures... but when the ambiant temp drops to sub freezing... my compressor won't spool-up for love nor money. This solved the problem: What it is: A 100w heat-lamp directed at the compressor on my air compressor. I've been running this kludge for approx. 12 winters... replaced the bulb once. I turn on the air compressor heat-lamp in Oct. (after the first time it fails to spool-up) and turn it off in May (when flies start hatching). Link to comment Share on other sites More sharing options...
Members bellaskid Posted December 5, 2008 Members Share Posted December 5, 2008 You might want to take it to a guy that specializes in repairing/re-manufacturing starters and alternators on cars. Link to comment Share on other sites More sharing options...
Members W. M. Hellinger Posted December 5, 2008 Members Share Posted December 5, 2008 every time i have ever experienced things like this with motors - in the end i got a new motor.the fact that you can move it a little and it starts sounds like a brush/commutator issue but i thought these air compressors usually used inductance motors.i have a belt sander that uses brushes and works fine except the brushes are completely worn down. the sander is 30 years old and i cant find brushes for it so once in a while i have to give it a good thump to get it to start. I've made quite a few custom brushes in the past by filing down avaiable brushes to fit the brackets. Link to comment Share on other sites More sharing options...
Members agedhorse Posted December 5, 2008 Members Share Posted December 5, 2008 That's probably a brushless motor. In order of probability... starting capacitor then centrifugal starting winding cutout switch. Funny, I'll bet I have a good one sitting on my shelf. What HP, shaft size(diameter & length) and frame is it? I am moving and tossing lots of stuff like this. Maybe it's in the toss pile. Link to comment Share on other sites More sharing options...
Members kevinnem Posted December 5, 2008 Members Share Posted December 5, 2008 Funny, I'll bet I have a good one sitting on my shelf. What HP, shaft size(diameter & length) and frame is it? I am moving and tossing lots of stuff like this. Maybe it's in the toss pile. oh man ......... I got to ask, I am looking for the battery cover plate for a 1981 Yamaha Virago, right side, 920cc engine, .. you don't have one of those do you? Link to comment Share on other sites More sharing options...
Members Gary in NJ Posted December 5, 2008 Author Members Share Posted December 5, 2008 While I have checked the oil level, the fluid (30w) is original. There's something to do. I would think that a starter cap would be good or bad and that "cantankerous" would not be an available mode. I'll get the manufacturer & model number of the motor to see if that sheds any light on the situation. Link to comment Share on other sites More sharing options...
CMS Author Craig Vecchione Posted December 5, 2008 CMS Author Share Posted December 5, 2008 oh man .........I got to ask, I am looking for the battery cover plate for a 1981 Yamaha Virago, right side, 920cc engine, .. you don't have one of those do you? Hey Kev, post up some pics of the bike! A 920 Virago was the first motorcycle I rode, it was a friend's who taught me to ride. Oddly enough, I've never seen another 920 since. Link to comment Share on other sites More sharing options...
CMS Author Craig Vecchione Posted December 5, 2008 CMS Author Share Posted December 5, 2008 Back OT (or back on off-topic, lol), my first thought was that you should check the compressor to make sure it's not starting to seize...the fact that rotating the motor/comp a little allows it to start leads me to think it's got failing bearings. Be careful before you go spending money on this. Many homeowner compressors are not made to last very long, and when one component is worn out, that often means the rest aren't far behind. Link to comment Share on other sites More sharing options...
Members W. M. Hellinger Posted December 5, 2008 Members Share Posted December 5, 2008 While I have checked the oil level, the fluid (30w) is original. There's something to do. 30wt. seems fairly heavy, but I believe 30wt. might have been what my NAPA compressor had original... and it had starting problems in cold weather. I believe the compressor oil I'm current running is 10wt. Changing the oil (to probably a lighter weight) and putting a heat lamp on it in cold weather has proven to be the fix for my hard starting compressor. Link to comment Share on other sites More sharing options...
Members Ear Abuser Posted December 5, 2008 Members Share Posted December 5, 2008 I have a Sears air compressor with exactly the same problem- I'm pretty sure it's the start cap gone bad, but since I only use the thing about once a month, I just hit the on switch and give the pulley a shove and away it goes. If the motor has a cylindrical blob about the size of soup can on the outside, then it uses a start cap. You can probably get the start cap at Grainger. (Also a good place for a replacement motor if you want to avoid the chinese Northern tool type replacement motor). I'd fix it, but the pinhole leaks in the tank are leading me to just buying a new compressor the next time I have a project that really needs it. In yet another topic swerve, after reading about the 100 watt light burning all winter, it got me wondering if Mark every got his electric bill resolved? (BTW if it was me,I would get a direct contact crankcase heater for a AC compressor from Grainger (about $5) It wraps around the crankcase so the improved heat transfer should allow you to use less watts. And I'd either put it on a timer or thermostat. But my day job is energy consulting) Link to comment Share on other sites More sharing options...
Members srp72ee Posted December 5, 2008 Members Share Posted December 5, 2008 It's probably just a Single Phase Induction Motor. I agree, it may just be a starting cap. Since it will eventually start, that tells me the winding is good. The capacitors are relatively cheap at heating and cooling stores. If you are able to buy from Grainger, you can get them there. If you want a new motor, PM me with the HP and frame size. I don't normally deal with motors that small... Link to comment Share on other sites More sharing options...
Members W. M. Hellinger Posted December 6, 2008 Members Share Posted December 6, 2008 My experience suggests that when a cap on a motor goes bad, or if the starting winding system is defunct, the motor won't have enough oomph to spool up on it's own with little or no load. IOW: Rotating the compressor back a little so the motor isn't trying to start dead against the peak of the compressor's compression isn't going to do it... leading me to doubt the problem is with the motor... well... it's partially a problem with the motor since I believe consumer grade air compressors are probably generally engineered and equipped with "adequate HP motors" for the application under reasonable conditions. I suspect the motor has MOL the same amount of oomph as it had when it was new. I suspect the real problem is elsewhere. Possibilities: 1) I suspect possibly something's defunct with the compressor's pressure bleed-off system. I believe the compressor is possibly equipped with a bleed-off system so the motor doesn't have to start the compressor against the pressurized air in the tank. I believe either the bleed-off valve is stuck shut or broken, or the check-valve between the compressor and the tank is not closing properly when the compressor shuts off. Or possibly the check valve is sticking shut? 2) Possibly the compressor's crankcase oil is contaminated enough to make it thick enough to increase the load on the motor? 3) Possibly the air filter is fairly dirty (even if it looks clean on the surface)? 4) Possibly the compressors valves (reed valves?) are getting sticky? 5) Possibly the compressor has broken piston rings which are dragging on the cylinder walls? 5) Possibly the belt is over-tightened or somehow worn in a manner that it's dragging on the pullies? 6) Possibly the compressor has a siezed or dragging bearing? Link to comment Share on other sites More sharing options...
Members W. M. Hellinger Posted December 6, 2008 Members Share Posted December 6, 2008 In yet another topic swerve, after reading about the 100 watt light burning all winter(BTW if it was me,I would get a direct contact crankcase heater for a AC compressor from Grainger (about $5) It wraps around the crankcase so the improved heat transfer should allow you to use less watts. And I'd either put it on a timer or thermostat. But my day job is energy consulting) I tried the crankcase heater and also tried a timer on my compressor... and neither conclusively (reliably) solved the problem. The thermostat idea could possibly save a little money... possibly... except where the air compressor is installed, the temp stays fairly consistently too cold for the compressor to reliably start (between approx. 40F and 20F) from approx. Halloween till approx. Madras Gras time. The heat lamp has proven to be the best solution. Our electric power here costs approx. 6 cents/KWH. The 100w heat lamp costs approx. 14 cents a day to keep my compressor warm, which costs me approx. $20 to burn that 100w bulb all winter. Otherwise, my compressor works a-ok, fine... and has been working a-ok fine (with the heat lamp) for approx. 12 years. We use compressed air throughout the day every day in the shop. I determined the motor on my air compressor just doesn't have quite enough start-up power to start my compressor when it's cold (approx less than 45F)... and I have the compressor installed in a remote (unheated) portion of my warehouse (so we don't have to listen to the racket when it's running). I've considered getting a higher HP motor for the compressor or changing the motor pulley to a smaller size, or even outfitting the drive with a centrifugal clutch, but it's arguable the total cost of any of those options isn't cost effective over my existing functional "fix" of the problem. Reliabile compressed air is important to me... even if it costs an additional $20/year to burn a heat lamp, since a failure of the compressed air system cascades other more expensive problems... primarily being the resulting failure of my waste oil furnace heating system for the shop, since the waste oil funace requires compressed air to function... so if the air compressor doesn't start, then the heat in the shop stops, then the water pipes in the shop could freeze and break, and/or our paints and glues could freeze, and/or the resident shop cat could get cold and develop a bad attitude, etc... Link to comment Share on other sites More sharing options...
Members Scafeets Posted December 6, 2008 Members Share Posted December 6, 2008 Just like everything else in life, it'll work better after you clean it and lube it... Link to comment Share on other sites More sharing options...
Members xmlguy Posted December 6, 2008 Members Share Posted December 6, 2008 Any chance you might have a voltage drop on the circuit? Anything else on the circuit? Good heavy gage conductors? Just a thought. Link to comment Share on other sites More sharing options...
Members Gary in NJ Posted December 7, 2008 Author Members Share Posted December 7, 2008 "1) I suspect possibly something's defunct with the compressor's pressure bleed-off system. " Problem exists whether the tank is full or empty.2) Possibly the compressor's crankcase oil is contaminated enough to make it thick enough to increase the load on the motor? I agree, and will change the oil as it is 20 years old. 3) Possibly the air filter is fairly dirty (even if it looks clean on the surface)? While I don't think this is attributing to the starting problem, its aAnother thing to change 4) Possibly the compressors valves (reed valves?) are getting sticky? Possible, but it manages to fill OK (for a 20 year old compressor, that is). 5) Possibly the compressor has broken piston rings which are dragging on the cylinder walls? Possible, but it manages to fill OK (for a 20 year old compressor, that is). 5) Possibly the belt is over-tightened or somehow worn in a manner that it's dragging on the pullies? Self tightening -as long as the motor pivots on the pin 6) Possibly the compressor has a siezed or dragging bearing? The compressor seems to function well. Any chance you might have a voltage drop on the circuit? Anything else on the circuit? I checked the voltage - 125VAC. Nothing else on the circuit. it may just be a starting cap I changed the run cap a few weeks ago, but for some reason, didn't order a start cap. When the oil gets changed next week, so will the cap. Thanks all of the input. I have an emotional attachment to this tool and can't seem to let it go. Link to comment Share on other sites More sharing options...
Members W. M. Hellinger Posted December 7, 2008 Members Share Posted December 7, 2008 I checked the voltage - 125VAC. Nothing else on the circuit. The line voltage at the motor stays steady @ 125v during start-up? Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.