I got an Air Compressor in my garage. It's just a small household
type, not the large ones used in service garages. The motor is free,
and turns easily by hand. The other day I plugged it in and had to
fill a tire. It started, but would quit running for a few seconds
then go again. At the time I thought the pressure control was dying
that turns it off and on, but it did finally pump up to full pressure.
Today I plugged it in again, and the motor will not start. It hums,
but will not start at all. The weird part is that all the lights in
the garage get very dim, which includes the compact florescents in the
ceiling lights, and the 100W indecesant flood light outside. What is
even more strange, is the fact that the breakers do not trip, even
after leaving it plugged in for approx. one minute. What the heck is
Note, the motor is a 1/3HP 120V capacitor start motor. The wiring in
the garage is all new as of one year ago. The lights are on a
different circuit than the compressor outlet, which is mounted
directly below the breaker box, and has its own 20A breaker.
Therefore, I can be sure the wiring is not at fault. Just for the
heck of it, I have an outdoor receptacle on a GFCI. I plugged the
compressor into that outlet, and the GFCI did not trip either.
I have done wiring and electrical stuff for many years, and this one
is just too weird....... All I can figure is that the capacitor is
bad, but I'd still think the breaker would trip.
Anyone got any ideas?
PS. My 240V well pump also runs off the garage panel, and works fine.
I have Cutler Hammer breakers in there. You must know about a problems
with ITE breakers????
However, I went in the garage to saw a board and the saw would not run
at full speed, and the lights all went very dim. That clued me there
is another problem, and in the wiring, not the motor. Since the water
pump is OK, that means I must have a bad neutral. Just for the heck
of it, I plugged in a spare 1/2HP motor. The lights inside the garage
went OUT. The floodlight on the outside of the garage BURNED OUT.
The wiring in the garage is new, but I opened the breaker box and
everything is tight and looks fine. I suspect the overhead wires from
the main pole to the garage are at fault. This is a farm. The house
barn, and another shed are all OK. They all have a separate overhead
line from the main pole, except the house which is underground. There
has got to be a bad neutral connection overhead. I looked up there
with a flashlight (it's nighttime). All wires are physically
connected, but one of the neutrals has got to have a bad connection.
I have to wait until daytime to go up there. Not what I didn't want
to do today. I hate going up on poles anytime. I am no fan of
heights, especially on ladders against round poles. I have a feeling
I have no neutral at all, just the ground rod is giving me enough
ground to light the lightbulbs.
PS. Just for the heck of it, I just went outside and ran my 100 foot
extension cord from that other shed to the garage, and the air
compressor works just fine.
Does anything get brighter when you plug run the motor? I can see that the
motor causes one circuit to get overloaded, which causes a second circuit to
dim; but unless something gets brighter, your story does not make sense (at
least not with a floating neutral)
Also, you say the 1/3hp motor causes the floodlight to dim, and the 1/2hp
motor burns it out. That can't be. Or did I misread this?
Nothing got brighter, ALL lights got real dim, and the flood bulb was
nearly off, just an orange glow.
I plugged the 1/2HP motor in a different circuit. That is when it
However, I found the problem. I was looking in the breaker box when I
plugged in the motor again, and I heard a pop sound. I decided to
wiggle breakers and when I wiggled the main breaker the motor sped up
and the lights got brighter for a second. That's when I shut off the
power and pulled the main breaker. Sure enough, the contacts were
spread apart too much on one side of the line. That breaker always
looked crooked, and now it's straight. I think it was tipped and the
contacts on one side of the line were off to the side of the panel
pegs, instead of being clamped around them. I tightened them with a
plyers, put the breaker back, turned on the power, and everything
Therefore, it appears that one side of the line was not making good
contact. This explains why my welder tended to shut off for a few
seconds every once and a while, when I was running it on high. This
started right after I replaced the old wiring and old fuse box.
What I dont understand is why my 220V submercible well pump still
worked. It's on the same main breaker, (plus its own 20A dual
breaker). It must have been running on 110V, but still worked fine.
This makes no sense.
Now that everything is fixed, I have one question. How in the heck
can the lights work at all on that side of the line, and what caused
them to get dim when I plugged in a motor? Also, it would appear that
the flood light got too much voltage, since it got real bright and
blew the second I plugged in the 1/2HP motor?
Perhaps at 220 volts the pump uses less current than the 120 volt motor
driven items, thus less of a voltage drop. Even if the voltage drop was,
say 50 volts, the 220 volt motor would still have a higher ratio of
this is Turtle.
The loose connection just came into play with what you said here. It can be a
Loose neutral but it can be a loose hot too. Also you have contactor in the
breaker that can be burning and causing the shot. They have contactor just like
switches to turn it off and on.
Yes , I have seen a few problem with ITE breaker here lately.
Sounds like the motor start switch contact is pitted and not making
connection anymore. Take the motor apart and the centrifugal switch is
inside one of the end covers. Clean the contacts, if possible -- sometimes
they are so pitted that they must be replaced -- and then put the whole
thing back together again.
On Sat, 11 Sep 2004 10:47:23 GMT, "berkshire bill"
That is a good suggestion, but I took the belt off and it still did
not run. If you read my other recent post, I suspect I have a missing
overhead neutral. Now if I can only figure out where !!!!
I doubt you are missing a neutral. Try plugging the motor someplace else
in the house on a different circuit. Same thing?
I suspend the motor bearings are going. Since there is a strong load, but
no short, the breaker will not pop. As long as the load is less than the
breaker rating, it will hold but cause lights to dim.
Did you spin the motor by hand? That will give you a clue. Could be a few
other things also. as was already pointed out.
Ed, I think he is on the right track, there is a bad connection somewhere.
With the poor neutral the voltage drops on the 120 volt circuits that causes
the amps to drop also, less voltage to push = less amp draw, so the breakers
hold. Why would lighting on a differant circuit on the same panel dim or go
out when the motor starts? A 1/3 HP motor should not cause much more than a
flicker in the lights when stalled.
I would try the compressor off the house panel for kicks before going crazy,
but my bet is the compressor is ok.
He did try it on a different circuit and it ran OK. Yes, a 1/3 HP would
only draw that much if it at a locked rotor. I wnet for the more common
type problem, but in this case, it was a less obvious one.
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