MS

"Mike S."

15/01/2006 3:53 PM

Repair my Emglo AM78-HV4V air compressor

We were using our Emglo and shut it down for a lunch break. When we came
back and tried to start it again all we got was a load electrical hum and
sometimes it would pop our 15 amp breaker.

I pulled the compressor/electric motor unit loose from the rest of the
compressor so I could get to its guts. When I turned the fan blade by hand
(it turned very easily) I could hear the compressor piston working. I even
connected the AC power back up but still heard the hum. When I gave the fan
a twist the motor started running the compressor. However, the motor won't
start the compressor on its own.

I tried a quick test of the start-up capacitor with my multimeter and it
appears to be OK. It slowly climbs in ohms until infinity. Reversed the
probes and it does the same thing. Sounds like the capacitor is OK to me.

I wanted to pull the electric motor loose from the case so I could see the
brushes and rotor. I removed all the mounting screws from everything I
could see, but I can't seem to pull the unit apart to get to the motor.
Everything is loose and I can twist the case a few degrees, but I can't pull
it apart.

Anybody know how I can get the motor out so I can look at its guts. Any
help is appreciated. Pretend I'm a dunce and be pretty specific.

Thanks,
Mike


This topic has 22 replies

Gn

"Gary"

in reply to "Mike S." on 15/01/2006 3:53 PM

15/01/2006 4:11 PM

Just because a cap doesn't leak at the low voltage provided by a VOM
does not mean it isn't leaking at working voltage. Try substituting
another cap and see if it helps. My outside air conditioning unit was
doing exactly the same thing. Diagnosis: bad starting cap. If your
motor uses two caps (one for start, one for run) check the centrufugal
switch
that controls the caps to see if it is broken.
Good luck. 73 Gary

GE

Grant Erwin

in reply to "Mike S." on 15/01/2006 3:53 PM

15/01/2006 4:13 PM

Mike S. wrote:

> We were using our Emglo and shut it down for a lunch break. When we came
> back and tried to start it again all we got was a load electrical hum and
> sometimes it would pop our 15 amp breaker.
>
> I pulled the compressor/electric motor unit loose from the rest of the
> compressor so I could get to its guts. When I turned the fan blade by hand
> (it turned very easily) I could hear the compressor piston working. I even
> connected the AC power back up but still heard the hum. When I gave the fan
> a twist the motor started running the compressor. However, the motor won't
> start the compressor on its own.
>
> I tried a quick test of the start-up capacitor with my multimeter and it
> appears to be OK. It slowly climbs in ohms until infinity. Reversed the
> probes and it does the same thing. Sounds like the capacitor is OK to me.
>
> I wanted to pull the electric motor loose from the case so I could see the
> brushes and rotor. I removed all the mounting screws from everything I
> could see, but I can't seem to pull the unit apart to get to the motor.
> Everything is loose and I can twist the case a few degrees, but I can't pull
> it apart.
>
> Anybody know how I can get the motor out so I can look at its guts. Any
> help is appreciated. Pretend I'm a dunce and be pretty specific.
>
> Thanks,
> Mike
>
>

It's probably still the start cap. Given the relatively low expense of
electrolytic capacitors, I'd just replace the start cap and see if that fixes
it. My guess is it will.

Take off the "bubble" on the side of the motor and look at the start cap. It may
obviously be defective, or maybe you can just get the numbers off it and take
them to Grainger or wherever you go to buy a new one. Easy to splice it back in,
simple fix. Even if that isn't the problem it won't hurt and it will probably
only cost you like $7.

GWE

bR

[email protected] (Robert Bonomi)

in reply to "Mike S." on 15/01/2006 3:53 PM

16/01/2006 8:06 PM

In article <[email protected]>,
Mike S. <[email protected]> wrote:
>Hi Bob,
>
>> The only thing I can think of is the unloader (if your compressor has
>one).
>> If it's sticking, there may be too much back pressure, and the motor isn't
>> powerful enough to overcome it.
>>
>Don't think that's the case. When I removed the compressor/motor unit from
>the rest of the compressor it also removed it from all the air tanks etc.
>Like I said, spinning the compressor by hand was very easy. Its just that
>the motor won't start on its own.

That virtually guarantees that the problem is one of two things:
1) stuck/bad (open) centrifugal switch for the start windings on the motor
2) bad start cap.


I'd be tempted to try some 'impact engineering' to see if one can induce
the centrifugal switch to close. Proceed at your own risk. <grin>

KS

Ken Sterling (Ken Sterling)

in reply to "Mike S." on 15/01/2006 3:53 PM

17/01/2006 2:50 AM

>We were using our Emglo and shut it down for a lunch break. When we came
>back and tried to start it again all we got was a load electrical hum and
>sometimes it would pop our 15 amp breaker.
>
>I pulled the compressor/electric motor unit loose from the rest of the
>compressor so I could get to its guts. When I turned the fan blade by hand
>(it turned very easily) I could hear the compressor piston working. I even
>connected the AC power back up but still heard the hum. When I gave the fan
>a twist the motor started running the compressor. However, the motor won't
>start the compressor on its own.
>
>I tried a quick test of the start-up capacitor with my multimeter and it
>appears to be OK. It slowly climbs in ohms until infinity. Reversed the
>probes and it does the same thing. Sounds like the capacitor is OK to me.
>
>I wanted to pull the electric motor loose from the case so I could see the
>brushes and rotor. I removed all the mounting screws from everything I
>could see, but I can't seem to pull the unit apart to get to the motor.
>Everything is loose and I can twist the case a few degrees, but I can't pull
>it apart.
>
>Anybody know how I can get the motor out so I can look at its guts. Any
>help is appreciated. Pretend I'm a dunce and be pretty specific.
>
>Thanks,
>Mike
>
>
Probably starting switch inside the motor that connects the cap to the
windings. Try tapping on the end bell of the motor when you try to
start it.... The "points" eventually get a bit pitted and blackened,
and typically cleaning them up is all it will need....
HTH
Ken.

KS

Ken Sterling (Ken Sterling)

in reply to "Mike S." on 15/01/2006 3:53 PM

18/01/2006 3:02 AM

>
><Ken Sterling (Ken Sterling)> wrote in message
>news:[email protected]...
>> Probably starting switch inside the motor that connects the cap to the
>> windings. Try tapping on the end bell of the motor when you try to
>> start it.... The "points" eventually get a bit pitted and blackened,
>> and typically cleaning them up is all it will need....
>> HTH
>> Ken.
>
>So if that's the case, how do I get to them?
>
>Mike
>
>
Mike,
Having trouble finding any kind of info on that particular model -
AM78-HV4V...... From your original post, it sounds like this is just
a motor, with a pulley, driving a larger pulley via a belt, as you
mentioned giving the "fan" a spin. Anyway, ya gotta locate the motor,
and take the end bell off to gain access to a centrifugal switch
internal to the motor. The switch has a set of contact points on it
which close with the motor at rest, putting the cap into the circuit.
When the motor starts up, centrifugal force causes the switch to open
up and takes the cap out of the circuit until it's needed for the next
start. Arcing, pitting, dust, dirt, etc., can keep the contacts from
making contact with each other when the motor is at rest. I suggested
tapping on the end bell of the motor when trying to start it as
sometimes that will let the contacts actually touch each other and get
the cap in the circuit to start the motor. That will tell you if the
cap is good or not as well as letting you know that the contacts are
dirty. I can't see the motor so it's hard to tell you how to take it
apart. Sorry.
Ken.

MM

"Mike Marlow"

in reply to "Mike S." on 15/01/2006 3:53 PM

16/01/2006 10:00 PM


"Ignoramus7637" <[email protected]> wrote in message
news:[email protected]...
> On Mon, 16 Jan 2006 21:02:59 -0500, Joseph Gwinn <[email protected]>
wrote:
> > In article <[email protected]>,
> > Ignoramus7637 <[email protected]> wrote:
> >
> >> I am surprised about the cost of caps that you were quoted. They
> >> actually should cost a lot less. I have a few start caps that I bought
> >> new for like $3 apiece, each about 180 uF. I can sell you a couple for
> >> the same price, I have too many. If you arer local to Chicagoland, I
> >> can loan you some.
> >>
> >> Can you remove belt (if it is a belted compressor) and see if the
> >> motor starts by itself without a load?
> >
> > Another test is to put a pull rope in the pulley (with no compressor),
> > turn the AC power on, and try to start it like a gasoline engine. Or a
> > RPC without pony motor or caps.
>
> Yes, that's a good test, but make sure that all rope is gone off the
> shaft before you turn AC on (could sound obvious, but needs to be
> said).
>

Lots easier just to give the pulley a spin by hand.

--

-Mike-
[email protected]

WB

"William B Noble (don't reply to this address)"

in reply to "Mike S." on 15/01/2006 3:53 PM

17/01/2006 10:56 PM

If you were quoted $50 for a capacitor, I'd seriously try to find
another place to deal with - what exact value capacitor do you need?
did you check local electronics supply/surplus houses (be sure to say
it's a motor start capacitor) - the last one I bought (three days ago)
was 600 uf at 220VAC for $12, generally lower capacitance values are
less expensive.

Bill

www.wbnoble.com

to contact me, do not reply to this message,
instead correct this address and use it

will iam_ b_ No ble at msn daught com

MS

"Mike S."

in reply to "Mike S." on 15/01/2006 3:53 PM

17/01/2006 7:40 AM


"Ignoramus7637" <[email protected]> wrote in message
news:[email protected]...
> I am surprised about the cost of caps that you were quoted. They
> actually should cost a lot less. I have a few start caps that I bought
> new for like $3 apiece, each about 180 uF. I can sell you a couple for
> the same price, I have too many. If you arer local to Chicagoland, I
> can loan you some.
>
> Can you remove belt (if it is a belted compressor) and see if the
> motor starts by itself without a load?
>
No belt. And when the motor/compressor unit was sitting on the bench it
still wouldn't start. If I gave the motor fan a spin and applied power it
started to run - although the start up time was very slow.

Mike S.


Ii

Ignoramus7637

in reply to "Mike S." on 15/01/2006 3:53 PM

16/01/2006 6:36 PM

I am surprised about the cost of caps that you were quoted. They
actually should cost a lot less. I have a few start caps that I bought
new for like $3 apiece, each about 180 uF. I can sell you a couple for
the same price, I have too many. If you arer local to Chicagoland, I
can loan you some.

Can you remove belt (if it is a belted compressor) and see if the
motor starts by itself without a load?

i

On Mon, 16 Jan 2006 07:38:31 -0800, Mike S. <[email protected]> wrote:
> Hi Grant,
>
>> It's probably still the start cap. Given the relatively low expense of
>> electrolytic capacitors, I'd just replace the start cap and see if that
> fixes
>> it. My guess is it will.
>>
>> Take off the "bubble" on the side of the motor and look at the start cap.
> It may
>> obviously be defective, or maybe you can just get the numbers off it and
> take
>> them to Grainger or wherever you go to buy a new one. Easy to splice it
> back in,
>> simple fix. Even if that isn't the problem it won't hurt and it will
> probably
>> only cost you like $7.
>>
> Well, not quite. I've been told by two repair houses that this cap costs
> $50. I want to make sure it's dead before I replace it.
>
> Thanks,
> Mike
>
>


--

MS

"Mike S."

in reply to "Mike S." on 15/01/2006 3:53 PM

16/01/2006 7:38 AM

Hi Grant,

> It's probably still the start cap. Given the relatively low expense of
> electrolytic capacitors, I'd just replace the start cap and see if that
fixes
> it. My guess is it will.
>
> Take off the "bubble" on the side of the motor and look at the start cap.
It may
> obviously be defective, or maybe you can just get the numbers off it and
take
> them to Grainger or wherever you go to buy a new one. Easy to splice it
back in,
> simple fix. Even if that isn't the problem it won't hurt and it will
probably
> only cost you like $7.
>
Well, not quite. I've been told by two repair houses that this cap costs
$50. I want to make sure it's dead before I replace it.

Thanks,
Mike

UO

in reply to "Mike S." on 16/01/2006 7:38 AM

16/01/2006 5:24 PM

If two repair houses told you $50 for the start capacitor then you are
being held up with out a gun. Those greedy bastards are not happy with a
100% mark up to sell at $15 then screw them.

Ii

Ignoramus26433

in reply to "Mike S." on 15/01/2006 3:53 PM

16/01/2006 12:23 AM

Like others, I cannot think of anything beside the cap.

i

On Sun, 15 Jan 2006 15:53:43 -0800, Mike S. <[email protected]> wrote:
> We were using our Emglo and shut it down for a lunch break. When we came
> back and tried to start it again all we got was a load electrical hum and
> sometimes it would pop our 15 amp breaker.
>
> I pulled the compressor/electric motor unit loose from the rest of the
> compressor so I could get to its guts. When I turned the fan blade by hand
> (it turned very easily) I could hear the compressor piston working. I even
> connected the AC power back up but still heard the hum. When I gave the fan
> a twist the motor started running the compressor. However, the motor won't
> start the compressor on its own.
>
> I tried a quick test of the start-up capacitor with my multimeter and it
> appears to be OK. It slowly climbs in ohms until infinity. Reversed the
> probes and it does the same thing. Sounds like the capacitor is OK to me.
>
> I wanted to pull the electric motor loose from the case so I could see the
> brushes and rotor. I removed all the mounting screws from everything I
> could see, but I can't seem to pull the unit apart to get to the motor.
> Everything is loose and I can twist the case a few degrees, but I can't pull
> it apart.
>
> Anybody know how I can get the motor out so I can look at its guts. Any
> help is appreciated. Pretend I'm a dunce and be pretty specific.
>
> Thanks,
> Mike
>
>


--

JG

Joseph Gwinn

in reply to "Mike S." on 15/01/2006 3:53 PM

16/01/2006 9:02 PM

In article <[email protected]>,
Ignoramus7637 <[email protected]> wrote:

> I am surprised about the cost of caps that you were quoted. They
> actually should cost a lot less. I have a few start caps that I bought
> new for like $3 apiece, each about 180 uF. I can sell you a couple for
> the same price, I have too many. If you arer local to Chicagoland, I
> can loan you some.
>
> Can you remove belt (if it is a belted compressor) and see if the
> motor starts by itself without a load?

Another test is to put a pull rope in the pulley (with no compressor),
turn the AC power on, and try to start it like a gasoline engine. Or a
RPC without pony motor or caps.

Joe Gwinn

Bb

"Bob"

in reply to "Mike S." on 15/01/2006 3:53 PM

15/01/2006 7:49 PM

The only thing I can think of is the unloader (if your compressor has one).
If it's sticking, there may be too much back pressure, and the motor isn't
powerful enough to overcome it.

"Ignoramus26433" <[email protected]> wrote in message
news:[email protected]...
> Like others, I cannot think of anything beside the cap.
>
> i
>
> On Sun, 15 Jan 2006 15:53:43 -0800, Mike S. <[email protected]> wrote:
> > We were using our Emglo and shut it down for a lunch break. When we
came
> > back and tried to start it again all we got was a load electrical hum
and
> > sometimes it would pop our 15 amp breaker.
> >
> > I pulled the compressor/electric motor unit loose from the rest of the
> > compressor so I could get to its guts. When I turned the fan blade by
hand
> > (it turned very easily) I could hear the compressor piston working. I
even
> > connected the AC power back up but still heard the hum. When I gave the
fan
> > a twist the motor started running the compressor. However, the motor
won't
> > start the compressor on its own.
> >
> > I tried a quick test of the start-up capacitor with my multimeter and it
> > appears to be OK. It slowly climbs in ohms until infinity. Reversed
the
> > probes and it does the same thing. Sounds like the capacitor is OK to
me.
> >
> > I wanted to pull the electric motor loose from the case so I could see
the
> > brushes and rotor. I removed all the mounting screws from everything I
> > could see, but I can't seem to pull the unit apart to get to the motor.
> > Everything is loose and I can twist the case a few degrees, but I can't
pull
> > it apart.
> >
> > Anybody know how I can get the motor out so I can look at its guts. Any
> > help is appreciated. Pretend I'm a dunce and be pretty specific.
> >
> > Thanks,
> > Mike
> >
> >
>
>
> --
>

MS

"Mike S."

in reply to "Mike S." on 15/01/2006 3:53 PM

17/01/2006 7:44 AM


> That virtually guarantees that the problem is one of two things:
> 1) stuck/bad (open) centrifugal switch for the start windings on the
motor
> 2) bad start cap.
>
>
> I'd be tempted to try some 'impact engineering' to see if one can induce
> the centrifugal switch to close. Proceed at your own risk. <grin>
>
I'd be glad to check the centrifugal switch - if I knew what it was and
where it's located. It's not on my exploded view diagram.

Mike

Ii

Ignoramus12063

in reply to "Mike S." on 15/01/2006 3:53 PM

18/01/2006 4:39 PM

On Wed, 18 Jan 2006 08:07:09 -0800, Mike S. <[email protected]> wrote:
> Hi Bill,
>
> Don't have it in front of me any more. Sent it home with my brother. But,
> if memory serves me correctly it's 60uF, 360VAC. The repair shop quoted
> $50.00, the Emglo (DeWalt?) website quoted $43.00. Pretty pricey item, I
> guess.

There are many starting caps/run caps/start kits on ebay. Check out


7576085987, HVAC MOTOR START CAPACITOR NEW 53-64 mfd 330 VAC M. About
$11 with shipping. I consider this price expensive, by the way. Your
dealer, though, is trying to rob you blind.

i

MS

"Mike S."

in reply to "Mike S." on 15/01/2006 3:53 PM

17/01/2006 7:42 AM


"Mike Marlow" <[email protected]> wrote in message
news:[email protected]...
>
> Lots easier just to give the pulley a spin by hand.
>

Already tried that. Motor starts, but very slowly.

Mike

MS

"Mike S."

in reply to "Mike S." on 15/01/2006 3:53 PM

16/01/2006 7:35 AM

Gary,

Thanks for the input. I'll try to find somebody local that can do a
heavy-duty test on this cap.

Mike

Ii

Ignoramus7637

in reply to "Mike S." on 15/01/2006 3:53 PM

17/01/2006 2:27 AM

On Mon, 16 Jan 2006 21:02:59 -0500, Joseph Gwinn <[email protected]> wrote:
> In article <[email protected]>,
> Ignoramus7637 <[email protected]> wrote:
>
>> I am surprised about the cost of caps that you were quoted. They
>> actually should cost a lot less. I have a few start caps that I bought
>> new for like $3 apiece, each about 180 uF. I can sell you a couple for
>> the same price, I have too many. If you arer local to Chicagoland, I
>> can loan you some.
>>
>> Can you remove belt (if it is a belted compressor) and see if the
>> motor starts by itself without a load?
>
> Another test is to put a pull rope in the pulley (with no compressor),
> turn the AC power on, and try to start it like a gasoline engine. Or a
> RPC without pony motor or caps.

Yes, that's a good test, but make sure that all rope is gone off the
shaft before you turn AC on (could sound obvious, but needs to be
said).

i

MS

"Mike S."

in reply to "Mike S." on 15/01/2006 3:53 PM

18/01/2006 8:07 AM

Hi Bill,

Don't have it in front of me any more. Sent it home with my brother. But,
if memory serves me correctly it's 60uF, 360VAC. The repair shop quoted
$50.00, the Emglo (DeWalt?) website quoted $43.00. Pretty pricey item, I
guess.

Mike

MS

"Mike S."

in reply to "Mike S." on 15/01/2006 3:53 PM

17/01/2006 7:45 AM


<Ken Sterling (Ken Sterling)> wrote in message
news:[email protected]...
> Probably starting switch inside the motor that connects the cap to the
> windings. Try tapping on the end bell of the motor when you try to
> start it.... The "points" eventually get a bit pitted and blackened,
> and typically cleaning them up is all it will need....
> HTH
> Ken.

So if that's the case, how do I get to them?

Mike

MS

"Mike S."

in reply to "Mike S." on 15/01/2006 3:53 PM

16/01/2006 7:41 AM

Hi Bob,

> The only thing I can think of is the unloader (if your compressor has
one).
> If it's sticking, there may be too much back pressure, and the motor isn't
> powerful enough to overcome it.
>
Don't think that's the case. When I removed the compressor/motor unit from
the rest of the compressor it also removed it from all the air tanks etc.
Like I said, spinning the compressor by hand was very easy. Its just that
the motor won't start on its own.

Thanks,
Mike


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