On Sat, 14 Sep 2013 21:06:49 -0400, Stormin Mormon
wrote:

Today (Saturday Sept 14, 2013) a friend gave me an
air compressor. Says when he ran it six months or
so ago, ran fine. Sears oilless, 12 gal tank. Said to
deliver 3.3 SCFM (think that's right) at 90 PSI.

I got home, the air all blew out the safety pressure
device. Spent a bunch of time on the Sears web site. The
web site has a BIG pdf that takes most of the computer
screen, can only read the parts list on the tiny edge of
the screen. Sears wants $31 and change, for the safety
valve. Amazon $22 or so. Went to the auto parts, they
said to go to the farm and garden store 20 miles away.
Just for grins, went to Lowe's, about two miles away.
They had one for eight bucks.

Good auto parts stores should have them too.

Got home, install the safety device. Compressor still
hisses, and won't come up to pressure. Some looking,
find the drain valve under the tank is open, and a lot
of very black water on my floor. Mop the black, close
the valve.

And the butterfly valves are always messy - if you have to roll it
outside, it never gets drained. Pull that stupid valve, put on a
street elbow, a short nipple to get clear of the tank, and a regular
1/8" or 1/4" ball valve and a barb fitting where you can attach a
hose. Then direct the hose into a bucket where you can catch the muck
water, or on a semi-permanent under the workbench route the hose
outside.

Decided to run the compressor through a cycle. Ran for
a while, and then sounded like fire crackers popping
about once a second. Look at the gauge, find it's up
to 120 PSI. So, the electric cut out needs adjusting.

I turned off the power, and bled the air down to about
80. Turn it back on. The compressor growled, but didn't
start.

Oh, bother, the unloader is bad too.

No, you didn't actuate the unloader by having the pressure switch hit
the high 'Off' setting - someone set it too high. And when you tried
starting it by just plugging it in again, the motor was still fighting
against head pressure and stalled.

Now you know what Locked Rotor Amps means, and you might have to find
and push a Reset Button on the motor.

Adjust the pressure switch so it kicks off when it's supposed to -
about 105 to 110 PSI - and try it again. Follow the cord, you'll hit
the pressure switch. Pop the top, there will be an adjustment screw
or nut dead center, and usually a notation as to which way is Up and
Down.

If the Unloader valve sits there and hisses and the tank slowly bleeds
out.... You need a new check valve going into the tank.

Standard item, should be right next to the safety valves at Lowes. But
call first, they can tell you. It's either 1/2" NPT in and out, or
5/8 Copper Tubing in and 1/2" NPT out.

I tried to take the cover off, to get at the unloader.
But one of the screws is rotted and stripped, and after
an hour I can't get it to come loose. I guess I'll load
the compressor in my van, and take it back tomorrow. I
can use a larger compressor, but this one is a loser.
And the guy who gave it to me cleaned out the unloader
on his other compressor. Maybe he can get this one
working.

I guess this just hasn't been my good week. Wheel fell
off the truck (for real) and missed the church picnic.
What next?

When you get it back, if he gets the pressure switch set right and the
unloader working, and it still has starting issues, see if the motor
has a Start Cap or a Run Cap. Cheap to try, often they get dried out
and go bad after 30 years.