Motor Won't Run Under Load

Great ideas Yahlasit. I also believe that the starter circuitry, whatever topology, is likely at fault.

I have some serious reservations about the validity of the information the OP has provided us. If this compressor was "brand new" then why was it sold "as is" and who found out that it would blow the circuit to sell it "as is"? What part would regularly blow, the built in circuit breaker or thermal switch on the motor of this compressor? What if the power distribution circuit breaker kept blowing when this compressor was turned ON? How did the OP determine that this motor was miswired and how was the wiring corrected?

You should have both a start and run capacitor....

Take it to a motor winding shop,dismantle and check

could it be a 3phase motor and you have a single phase supply?

Im with the others on this one. when you say it ran " perfectly'" does this mean you took an amp draw and temperature of the body of the motor or does it mean it just seemed to spin at the right speed?

Single phase motors by their very nature have low starting torque so it's no surprise that you can hold the pulley with your hand (not a wise idea by the way), so now you have to look at what's at the other end of the belt, the compressor. If the compressor is started against the tank pressure, even if empty, it takes a lot of torque to get it moving.

The way around this is a combination electromechanical control valve that controls the cycling of the motor and contains a valve called an unloader which vents the line from the compressor to the tank so the motor has minimal load on it (equivalent to removing your hand from the pulley). Once the unloaded compressor is rotating fast enough to create a decent pressure the valve closes its vent to the atmosphere and allows the output to go to the tank. I suspect that the unloader valve is stuck in the closed position forcing the compressor to start against pressure, something it won't be able to do.

It's easy to check for though, open the tank vent and and remove anything attached to the pressure port and see if it starts and runs and air comes out. if not then there may be a faulty compressor, an obstruction in the airline, or a faulty controller. It's a electromechanical system, you have to move on from the electrical motor and see if the mechanical side is working properly as well.

you are right, this motor should have lots of power

it is a Marathon electric model 5KCR48TN2582Y

ithe motor sits on top of a HuskyPro portable 30 gallon compressor tank.

it is definitely a 110 volt single phase motor

I think the capacitors are the problem, and I think they might have been changed by someone else.

I contacted Marathon Electric and gave them the information to see if they could tell me which capacitors should go in this motor, but they have not answered me as of yet.

The 'model#' was probably an "OEM_Specific" part-run... (for Husky).

We are all, by now, *assuming* that the motor you are dealing with looks more like the one on the right ("capacitors", plural) than the one on the left (both Marathons).

[[ You *could* start-off such a thread (as I wish that ALL posters would!) with any-and-all complete motor-nameplate data (including hp / rpm!)... as well as the compressor model#... (numerous different motors will be found atop a "30 gallon tank")... and a photo or two...

Here's hoping you get the (combination) "Wiring-&-Capacitors" correct...!

you are right

the motor looks like the one on the right

I still think the problem is with one of the capacitors

and that the capacitors in there are not correct

I have tried to contact Marathon Electric to see if they could enlighten me as to which capacitors should go in there, but I have not been able to get a response from them as of yet

I would like to about this motor, Please check the manual of the machine. Then check what you done on it. Some time we know something different than what actually inside the manual.

So, you will have an idea about it. As you said that machine is new, it should come with some warranty. If yes, then take to their authorize dealer.

If it is out the time then follow the other procedure....!

the motor is a marathon electric motor

model 5KCR48TN2582Y

120 volt single phase

I also think that the capacitors are the problem but I am not sure that the capacitors in the motor are the correct ones. I think maybe someone changed them before I purchased it.

I have contacted the company that manufactures the motor 2 times already to see if they would tell me which capacitors go in this motor but they have not responded. I think that as a last resort I will take it to a place that fixes motors. I hate to buy a new one because this one starts and works, it just has no power when I put some tension on the pulley.

You seem hyper focused on the capacitor issue. it's highly unlikely. If the caps were incorrect, either it would never start, or it would start, but the caps would heat up and pop.

In the realm of troubleshooting, it is always best to BEGIN with the simplest things FIRST, not the more bizarre, because the chances are far greater that the issue is more simple than it is more complex.

Focusing on someone having disassembled the motor, changed the capacitors, and reassembled the motor is far far less likely than what RamConsultant said, that the unloader valve is stuck. To my mind the problem has always been the bad unloader, but someone before you did the same thing, hyper focused on a less likely thing, that the motor voltage was wrong, and tried that first. Then you bought it and the motor voltage WAS wrong, but fixing that did not cure the original problem, that the unloader was stuck.

Marathon would have sold a custom OEM motor like that in lots of 10-50,000 units to Husky for dirt cheap with the expressed understanding that as an OEM motor, they would NOT handle any warranty issues from the field. That would be Husky's responsibility. So your emails or phone calls are going straight to the trash, they are never going to respond to you. If anything, they MIGHT be forwarding this on to Husky, but they are unlikely to respond either. Most likely, the initial problem was found and Husky, like most high volume consumer goods OEMs, determined that it was far cheaper to scrap this than it was to fix it. So they instructed the dealer to smash it and gave them a replacement unit. The dealer however, looking to make more money, sold it "as is" to you; free money. You now own something that Husky and everyone else determined was not worth fixing because of the labor involved. If you can get an exploded parts manual for it and can identify the unloader, and you can buy a replacement or disassemble it to try to figure out what is wrong with it, you might get it working. But the labor and time involved is likely more than the price you paid for it. That's why it was scrapped and should NOT have been re-sold.

"bizarre" is always so much more fun to uncover!

Here's a silly idea. Buy a new electric motor. Then you can find out if the air compressor is broken, too.

GA.. it's brilliant....

I have an older compressor where the motor works, so I will replace it with that one. But I know the compressor works because when I first fired it up it ran for about a minute and it did build up compression, so that's why I think it has to be the motor and not the compressor itself.

Once again the details slowly creep toward revelation. Does the motor die when the compressor tries to exceed tank pressure? What pressure did you achieve in that minute of operation before something stuck? Was that tank pressure ever relieved? Did you measure the inductance of the stator windings? Is the motor an induction or brushed motor configuration? Is there a velocity switch that drops out starter circuitry windings? What does the phrase "sell as is" mean to you?

Oh, I'm sorry but I'm repeating the thread.