Air Compressor Problem - Motor Stalls

[Sparks Fergusson]

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!

 

[TonyS]

[]

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!

If it's a DC motor, maybe it needs new brushes?

 

[Sansui Samari]

On Mar 3, 9:13 pm, hates...@invalid.invalid (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?

Thanks!

I agree to check the brushes, if it's not a brushless motor. Does the
unloader bleed the entire tank off? If so, then the check valve is
probably bad. It could also be that your shutoff set point has self
adjusted back. Say your fill point is at 95 lbs, and your shutoff
self adjusts down to around 95 lbs, it can cause it to continuously
turn on and off. I had a compressor that used to do this to me for a
while, until I put a little locktight on the adjustment screw. It
could be just a worn out pressure switch as well. Maybe the spring
has become weak in it.

 

[PeterD]

On Thu, 04 Mar 2010 05:13:31 GMT, hatespam@invalid.invalid (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.

>...

 

[GregS]

In article <4b8f3f2a.47238118@news.eternal-september.org>, hatespam@invalid.invalid (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]

In article <hmohsd$30o$1@usenet01.srv.cis.pitt.edu>, zekfrivo@zekfrivolous.com (GregS) wrote:

In article <4b8f3f2a.47238118@news.eternal-september.org>,
hatespam@invalid.invalid (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

 

On Thu, 04 Mar 2010 05:13:31 GMT, hatespam@invalid.invalid (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...

Compressor binding up.

 

[Bennett Price]

On 3/3/2010 9:13 PM, 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?

Thanks!
Do you know for sure that your gauge is correct? Maybe the compressor

and pressure switch are fine.

 

[Sparks Fergusson]

Sansui Samari <jimjam1942@gmail.com> wrote:

On Mar 3, 9:13=A0pm, hates...@invalid.invalid (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]

PeterD <peter2@hipson.net> wrote:

On Thu, 04 Mar 2010 05:13:31 GMT, hatespam@invalid.invalid (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]

zekfrivo@zekfrivolous.com (GregS) wrote:

In article <hmohsd$30o$1@usenet01.srv.cis.pitt.edu>, zekfrivo@zekfrivolous.com (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]

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!

 

On Thu, 04 Mar 2010 18:18:01 GMT, hatespam@invalid.invalid (Sparks
Fergusson)wrote:

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!

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

 

[Sparks Fergusson]

Bennett Price <bjprice@cal.berkeley.edu> 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.

 

[GregS]

In article <4b900ac7.22422346@news.eternal-september.org>, hatespam@invalid.invalid (Sparks Fergusson) wrote:

Bennett Price <bjprice@cal.berkeley.edu> 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

 

[Sparks Fergusson]

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]

zekfrivo@zekfrivolous.com (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.

 

On Thu, 04 Mar 2010 20:09:31 GMT, hatespam@invalid.invalid (Sparks
Fergusson)wrote:

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

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?

 

[Alan Douglas]

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

 

[Sparks Fergusson]

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.