KMinAF
Well-known member
I thought I would share my recent experience fixing my compressor in hopes it will benefit others.
I have an old Devilbis tank with a Harbor Freight twin cylinder pump and a no name 5hp 240v motor.
It has worked flawlessly for the past seven years powering my air tools, sand blaster, paint gun and plasma torch. The incident began with me turning it on and only getting a thunk noise, no humming or buzzing, no sparks or smoke. After that nothing, no response when turned on. I checked voltage and had 120 on each line. I searched the internet and a lot of people where replacing the capacitors and even though the failure description didn't quite match, capacitors are cheap and easy so I replaced them. No change. I removed the end of the motor and inspected the centrifugal switch and had good continuity with no carbon build up on the contacts.
Perplexed and out of options I took it to a local motor repair shop. A week later I paid them $120 and was told I had a faulty centrifugal switch which they replaced. Hmmm, well they are the professionals so I accepted their word.
I reinstalled The motor, plugged it back in and it barely worked, it struggled to spin the compressor even with no air pressure. I quickly turned it off, scratched my head in thought, then turned it back on. Nothing. I again checked voltage, compressor spun freely etc. I returned the motor to the shop, another week passed by, I picked it up and was told they had installed a faulty centrifugal switch which they replaced under warranty. Hmmm something doesn't feel right.
I again reinstalled the motor plugged it back in turned it on and nothing happened! I pulled out the multimeter and found 120 on the first line but only 40 on the second? Lots of head scratching. What if? I took the plug apart and found one of the wires had come loose from the blade! I made the repair plugged it in and flipped the switch, SUCCESS or so I thought. It sounded different and was laboring, struggling to spin the compressor, then it bogged down and stalled at around 90PSI. Snap, Darn, stuck in a ditch, golly gee and other politically correct words were said with great enthusiasm.
I checked the tank valve, the unloader valve, rechecked the plug wiring etc etc. At this point I threw in the towel and started pricing out a new compressor at which point I hurriedly picked up the towel and started a calmed down methodical recheck of everything starting with the wiring.
Plug wires? Check
Pressure switch connections? Check
Motor wire connections? Hey, this spade connector feels loose! The blade was between the rubber insulation and the connector. I reinstalled the connector, and flipped the switch. then Aerosmiths Back in the Saddle Again started blasting through my brain as the motor spun at full tilt, effortlessly generating 120PSI and shutting off just like it is supposed to!
Yes I am frustrated that I spent $40 on unnecessary capacitors and gave a $120 for questionable repair but I learned a whole lot about diagnostic techniques, current draw, multimeter use, how induction motors work, and to check all the simple stuff first.
I have an old Devilbis tank with a Harbor Freight twin cylinder pump and a no name 5hp 240v motor.
It has worked flawlessly for the past seven years powering my air tools, sand blaster, paint gun and plasma torch. The incident began with me turning it on and only getting a thunk noise, no humming or buzzing, no sparks or smoke. After that nothing, no response when turned on. I checked voltage and had 120 on each line. I searched the internet and a lot of people where replacing the capacitors and even though the failure description didn't quite match, capacitors are cheap and easy so I replaced them. No change. I removed the end of the motor and inspected the centrifugal switch and had good continuity with no carbon build up on the contacts.
Perplexed and out of options I took it to a local motor repair shop. A week later I paid them $120 and was told I had a faulty centrifugal switch which they replaced. Hmmm, well they are the professionals so I accepted their word.
I reinstalled The motor, plugged it back in and it barely worked, it struggled to spin the compressor even with no air pressure. I quickly turned it off, scratched my head in thought, then turned it back on. Nothing. I again checked voltage, compressor spun freely etc. I returned the motor to the shop, another week passed by, I picked it up and was told they had installed a faulty centrifugal switch which they replaced under warranty. Hmmm something doesn't feel right.
I again reinstalled the motor plugged it back in turned it on and nothing happened! I pulled out the multimeter and found 120 on the first line but only 40 on the second? Lots of head scratching. What if? I took the plug apart and found one of the wires had come loose from the blade! I made the repair plugged it in and flipped the switch, SUCCESS or so I thought. It sounded different and was laboring, struggling to spin the compressor, then it bogged down and stalled at around 90PSI. Snap, Darn, stuck in a ditch, golly gee and other politically correct words were said with great enthusiasm.
I checked the tank valve, the unloader valve, rechecked the plug wiring etc etc. At this point I threw in the towel and started pricing out a new compressor at which point I hurriedly picked up the towel and started a calmed down methodical recheck of everything starting with the wiring.
Plug wires? Check
Pressure switch connections? Check
Motor wire connections? Hey, this spade connector feels loose! The blade was between the rubber insulation and the connector. I reinstalled the connector, and flipped the switch. then Aerosmiths Back in the Saddle Again started blasting through my brain as the motor spun at full tilt, effortlessly generating 120PSI and shutting off just like it is supposed to!
Yes I am frustrated that I spent $40 on unnecessary capacitors and gave a $120 for questionable repair but I learned a whole lot about diagnostic techniques, current draw, multimeter use, how induction motors work, and to check all the simple stuff first.
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