Air Compressor Problem - Motor Stalls

Discussion in 'Electronic Repair' started by Sparks Fergusson, Mar 4, 2010.

  1. I'm having a problem with my 20 gallon, single stage electric air
    compressor. It's acting like the motor is underpowered - it pumps up
    to about 95 psi ok, but then the motor stalls. The unloader bleeds the
    pressure off, the motor restarts, runs for a couple of seconds, and
    then stops again...repeat...repeat...

    It worked fine for years (The pressure switch would shut it down at
    about 120 psi) but over the past few months, it's gotten worse and
    worse, and now will only make about 90-95 psi before the motor stalls.

    I cleaned and lubricated the compressor itself, and it spins freely
    and doesn't appear to be binding or otherwise have excessive friction.
    The check valve/unloader is working and the piping is all open and
    clear.

    It seems like the electric motor (1/3 hp) just no longer has the oomph
    it used to. It starts up fine, no humming, no smoking, no bad smells,
    no clunks. It just doesn't seem to have enough running torque to
    handle the load like it did before.

    Anyone have any ideas?

    Thanks!
    Sparks Fergusson, Mar 4, 2010
    #1
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  2. Sparks Fergusson

    PeterD Guest

    On Thu, 04 Mar 2010 05:13:31 GMT, d (Sparks
    Fergusson) wrote:

    >
    >I'm having a problem with my 20 gallon, single stage electric air
    >compressor. It's acting like the motor is underpowered - it pumps up
    >to about 95 psi ok, but then the motor stalls. The unloader bleeds the
    >pressure off, the motor restarts, runs for a couple of seconds, and
    >then stops again...repeat...repeat...


    Bad pressure switch. The unloader is part of the pressure switch so if
    it is being activated, the pressure switch is 'saying' that the
    pressure is sufficient. Maybe it is just mis-adjusted.

    >
    >It worked fine for years (The pressure switch would shut it down at
    >about 120 psi) but over the past few months, it's gotten worse and
    >worse, and now will only make about 90-95 psi before the motor stalls.


    Check the adjusting screws, and reset the cutoff back to 120 PSI.
    Confirm the cuton is at 95 PSI.

    >...
    PeterD, Mar 4, 2010
    #2
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  3. Sparks Fergusson

    GregS Guest

    In article <-september.org>, d (Sparks Fergusson) wrote:
    >
    >I'm having a problem with my 20 gallon, single stage electric air
    >compressor. It's acting like the motor is underpowered - it pumps up
    >to about 95 psi ok, but then the motor stalls. The unloader bleeds the
    >pressure off, the motor restarts, runs for a couple of seconds, and
    >then stops again...repeat...repeat...
    >
    >It worked fine for years (The pressure switch would shut it down at
    >about 120 psi) but over the past few months, it's gotten worse and
    >worse, and now will only make about 90-95 psi before the motor stalls.
    >
    >I cleaned and lubricated the compressor itself, and it spins freely
    >and doesn't appear to be binding or otherwise have excessive friction.
    >The check valve/unloader is working and the piping is all open and
    >clear.
    >
    >It seems like the electric motor (1/3 hp) just no longer has the oomph
    >it used to. It starts up fine, no humming, no smoking, no bad smells,
    >no clunks. It just doesn't seem to have enough running torque to
    >handle the load like it did before.
    >
    >Anyone have any ideas?
    >


    Check the line voltage while opperating at the motor.
    I can do that stall with a long extension cord.

    greg
    GregS, Mar 4, 2010
    #3
  4. Sparks Fergusson

    GregS Guest

    In article <hmohsd$30o$>, (GregS) wrote:
    >In article <-september.org>,
    > d (Sparks Fergusson) wrote:
    >>
    >>I'm having a problem with my 20 gallon, single stage electric air
    >>compressor. It's acting like the motor is underpowered - it pumps up
    >>to about 95 psi ok, but then the motor stalls. The unloader bleeds the
    >>pressure off, the motor restarts, runs for a couple of seconds, and
    >>then stops again...repeat...repeat...
    >>
    >>It worked fine for years (The pressure switch would shut it down at
    >>about 120 psi) but over the past few months, it's gotten worse and
    >>worse, and now will only make about 90-95 psi before the motor stalls.
    >>
    >>I cleaned and lubricated the compressor itself, and it spins freely
    >>and doesn't appear to be binding or otherwise have excessive friction.
    >>The check valve/unloader is working and the piping is all open and
    >>clear.
    >>
    >>It seems like the electric motor (1/3 hp) just no longer has the oomph
    >>it used to. It starts up fine, no humming, no smoking, no bad smells,
    >>no clunks. It just doesn't seem to have enough running torque to
    >>handle the load like it did before.
    >>
    >>Anyone have any ideas?
    >>

    >
    >Check the line voltage while opperating at the motor.
    >I can do that stall with a long extension cord.
    >
    >greg


    Is it oiless ?If so, check the bearing.

    greg
    GregS, Mar 4, 2010
    #4
  5. Sansui Samari <> wrote:

    >On Mar 3, 9:13=A0pm, (Sparks Fergusson) wrote:


    >I agree to check the brushes, if it's not a brushless motor.


    It's an AC induction motor, so no brushes. Could it be a capacitor
    issue?

    >Does the unloader bleed the entire tank off? If so, then the check valve is
    >probably bad.


    It's a combination check/unloader valve. I cleaned and lubricated it,
    and it appears to be working fine. The tank holds pressure - the
    unloader just vents the tube between the tank and the compressor.

    >It could also be that your shutoff set point has self
    >adjusted back.


    Good thought, but the pressure switch seems to be functioning well. I
    am getting around the problem by turning down the pressure below the
    point where the motor stalls. But, that's only about 90 psi, which is
    not as much as I'd like. Plus, the problem seems to be getting worse.

    Thanks!
    Sparks Fergusson, Mar 4, 2010
    #5
  6. PeterD <> wrote:

    >On Thu, 04 Mar 2010 05:13:31 GMT, d (Sparks
    >Fergusson) wrote:
    >
    >>
    >>I'm having a problem with my 20 gallon, single stage electric air
    >>compressor. ...

    >
    >Bad pressure switch. The unloader is part of the pressure switch so if
    >it is being activated, the pressure switch is 'saying' that the
    >pressure is sufficient. Maybe it is just mis-adjusted.


    Actually, it's a mechanical unloader (combination check
    valve/unloader, which I have already cleaned and lubricated.) It seems
    to be working well.

    >Check the adjusting screws, and reset the cutoff back to 120 PSI.
    >Confirm the cuton is at 95 PSI.


    The pressure swicth seems to be working fine. If I turn down the
    pressure adjustment, I can get the contactor to turn off the motor
    before it stalls, but that's only 90-95 psi or so. If I adjust it
    higher, the motor is unable to turn the compressor if the pressure is
    more than 95-100psi. It's definitely the motor stalling, not the
    pressure switch opening.

    Thanks!
    Sparks Fergusson, Mar 4, 2010
    #6
  7. (GregS) wrote:

    >In article <hmohsd$30o$>, (GregS) wrote:


    >>Check the line voltage while opperating at the motor.
    >>I can do that stall with a long extension cord.
    >>
    >>greg

    >
    >Is it oiless ?If so, check the bearing.
    >
    >greg


    Line voltage is OK, about 123 volts. It drops to around 121 volts when
    the motor stalls. Voltage drop across the pressure switch is minimal
    (less than a volt.) I'm not using an extension cord.

    The compressor is oil filled, and has oil in it (although it is rather
    old oil, come to think of it.) But, I can easily turn the compressor
    over by hand and it feels like it's moving freely, with no excess
    friction or binding.

    Thanks!
    Sparks Fergusson, Mar 4, 2010
    #7
  8. Meat Plow wrote:
    >
    >Compressor binding up.


    I can turn it easily by hand, so it doesn't appear to be binding.
    However, I don't have an easy way to check it when it's at full load.
    Any suggestions?

    Thanks!
    Sparks Fergusson, Mar 4, 2010
    #8
  9. Bennett Price <> wrote:

    >> Thanks!

    >Do you know for sure that your gauge is correct? Maybe the compressor
    >and pressure switch are fine.


    Well, it's been working for a long time, but over the past few months
    has been exhibiting the stalling issue.

    I guess the guage could be wrong, but I kind of know what 120psi
    "feels like" and it's not getting up to what it used to, either by the
    guage or by feel.
    Sparks Fergusson, Mar 4, 2010
    #9
  10. Sparks Fergusson

    GregS Guest

    In article <-september.org>, d (Sparks Fergusson) wrote:
    >Bennett Price <> wrote:
    >
    >>> Thanks!

    >>Do you know for sure that your gauge is correct? Maybe the compressor
    >>and pressure switch are fine.

    >
    >Well, it's been working for a long time, but over the past few months
    >has been exhibiting the stalling issue.
    >
    >I guess the guage could be wrong, but I kind of know what 120psi
    >"feels like" and it's not getting up to what it used to, either by the
    >guage or by feel.


    The compressor speed does not slow down normally, it just starts to
    sound a bit different under load.

    greg
    GregS, Mar 4, 2010
    #10
  11. Meat Plow wrote:

    >Current draw. 1/3 horse shouldn't draw more than 7 amps at 120 volts
    >or 3.5 amps at 240 volts.


    Nameplace current rating is 6.0 amps (I'm running on 120 volts.)

    I measured about 5 amps at startup (0 psi) rising to close to 6 when
    it stalls. When it stops turning, the current actually drops back
    closer to 5 amps, then increases as the motor starts turning again.

    The motor is also hot to the touch after pumping all the way up. I can
    hold my hand on it for maybe 6 or 8 seconds. I don't know if that's
    different from how it used to be, though.

    Thanks!
    Sparks Fergusson, Mar 4, 2010
    #11
  12. (GregS) wrote:

    >The compressor speed does not slow down normally, it just starts to
    >sound a bit different under load.


    It didn't used to, that's for sure. Now, it slows all the way to 0. :(
    Sparks Fergusson, Mar 4, 2010
    #12
  13. Sparks Fergusson

    Alan Douglas Guest

    Assuming it's a 120V/240V motor connected for 120, can you check to
    see if both run windings are actually connected? Perhaps a nut is
    working loose on the terminal plate inside the motor.

    Alan
    Alan Douglas, Mar 4, 2010
    #13
  14. Meat Plow wrote:

    >Can you disconnect the motor from the pump and run just the motor to
    >measure its no load amps? And to see if it heats up with no load?


    No load, it's drawing about 1.5 amps. It gets warm, but not as hot as
    it was under load.
    Sparks Fergusson, Mar 5, 2010
    #14
  15. Alan Douglas <> wrote:

    >Assuming it's a 120V/240V motor connected for 120, can you check to
    >see if both run windings are actually connected? Perhaps a nut is
    >working loose on the terminal plate inside the motor.


    Hmm, you might have something, there! This motor is probably 15+ years
    old, and has never had anything done to it. Could corrosion and/or
    loose connections account for the lack of power? I can certainly try
    cleaning and tightening anything I can get to.

    Thanks!
    Sparks Fergusson, Mar 5, 2010
    #15
  16. Meat Plow wrote:

    >What kind of motor is this? I didn't see you mention that. A 1/3 horse
    >induction motor should not draw 1.5 amps with no load.


    It's some sort of GE induction motor. I have the model number, but I
    can't find anything about it on the GE website or Google.

    What sort of problems would high no-load amp draw suggest?
    Sparks Fergusson, Mar 6, 2010
    #16
  17. "William R. Walsh"
    <> wrote:

    >Hi!
    >
    >You should check the pressure switch contacts to be sure they aren't
    >burned. If they look OK, check the wiring leading to the compressor.
    >Perhaps something is wrong there. (Be sure you shut the power off FIRST
    >or you could have a shocking experience.)


    Pressure switch contacts look OK, and there's minimal voltage drop
    across under load. Wiring looks OK, too.

    >Failing all of that, I'd check to see if the motor uses a run capacitor.
    >If it does, the capacitor is probably bad.


    There is a capacitor, but I'm not sure exactly what it does. I don't
    have a wiring diagram and can't find any info on the Manufacturer's
    website (GE.) I'll try to check the capacitor as best I can.

    Could a capacitor issue cause the motor to start fine, but not have
    enough power when running?
    Sparks Fergusson, Mar 6, 2010
    #17
  18. Sparks Fergusson

    Jamie Guest

    Sparks Fergusson wrote:

    > Meat Plow wrote:
    >
    >
    >>What kind of motor is this? I didn't see you mention that. A 1/3 horse
    >>induction motor should not draw 1.5 amps with no load.

    >
    >
    > It's some sort of GE induction motor. I have the model number, but I
    > can't find anything about it on the GE website or Google.
    >
    > What sort of problems would high no-load amp draw suggest?

    Bad bearings..
    and if it's a single phase motor.. check the starter cap, if it
    has one. most likely not much good any more..

    Also, you may have a centrifugal switch in the motor that isn't
    closing its contacts. Or, you could have an open winding!..
    Jamie, Mar 6, 2010
    #18
  19. Sparks Fergusson

    Alan Douglas Guest

    >>Assuming it's a 120V/240V motor connected for 120, can you check to
    >>see if both run windings are actually connected? Perhaps a nut is
    >>working loose on the terminal plate inside the motor.

    >
    >Hmm, you might have something, there! This motor is probably 15+ years
    >old, and has never had anything done to it. Could corrosion and/or
    >loose connections account for the lack of power? I can certainly try
    >cleaning and tightening anything I can get to.


    None of the other suggestions I've read, fit the symptoms. First
    would be low voltage to the motor under load, but you've already
    checked that. The starting capacitor is out of the circuit when the
    motor is up to speed. There's nothing left in circuit but the two run
    windings, wired in parallel.

    Alan
    Alan Douglas, Mar 6, 2010
    #19
  20. Sparks Fergusson

    PeterD Guest

    On Sat, 06 Mar 2010 09:09:57 -0500, Alan Douglas
    <> wrote:

    >>>Assuming it's a 120V/240V motor connected for 120, can you check to
    >>>see if both run windings are actually connected? Perhaps a nut is
    >>>working loose on the terminal plate inside the motor.

    >>
    >>Hmm, you might have something, there! This motor is probably 15+ years
    >>old, and has never had anything done to it. Could corrosion and/or
    >>loose connections account for the lack of power? I can certainly try
    >>cleaning and tightening anything I can get to.

    >
    >None of the other suggestions I've read, fit the symptoms. First
    >would be low voltage to the motor under load, but you've already
    >checked that. The starting capacitor is out of the circuit when the
    >motor is up to speed. There's nothing left in circuit but the two run
    >windings, wired in parallel.
    >
    >Alan


    And all those replies ignore the fact the unloader is operating (at a
    wrong, low pressure) which certainly doesn't point an evil finger at
    the motor at all...
    PeterD, Mar 7, 2010
    #20
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