[AT] Air compressor failure

[Mark Greer]

A couple observations from working on air compressors & shop air systems:

1) the pressure relief valves are often (not always) stamped with the
pressure they are supposed to pop off at, which is normally higher than the
cutout setting on the pressure switch and lower than the tank rating. YMMV

2) I suspect (as have others here) that the pump probably has too many
miles on it and is having trouble developing the last bit of pressure to
reach the cutout setting. I have picked up a few "broken" compressors for a
song over the years that wouldn't shut off. A quick easy "fix" to get them
back working is to adjust the cutout setting down a few psi until it
functions again. This is a 'band-aid" fix for a worn out pump but it will
usually buy you some more run time on an old machine. I'd explore this
option first. Most of the time I need air, I don't need the full psi the
compressor was built for.

3) don't always trust the gauge on the compressor. Many big box store
machines use cheap gauges that are fairly inaccurate, sometimes to the tune
of 5-10 psi. I have a high end glycerine-filled stainless-body 200 psi
gauge installed into a tee-fitting that I keep in my toolbox along with a
handful of adapters to use to work on air systems. I trust it, and it often
reads differently than the ones that come on compressors, especially lower
end units.

Mark Greer

On Tue, Dec 7, 2021 at 3:23 PM Jim Becker <mr.jebecker at gmail.com> wrote:

> If it was intended to operate up to 135#, as the giant label on the tank
> indicates, the relief valve won’t be anywhere near release pressure at
> 135#.  It probably trips at something more like 165# (just a guess).  In
> any case, if it is running forever at close to 135# and not building more
> pressure, the problem has nothing to do with the relief valve.  I would run
> through some of the checks others have suggested (oil level, clean intake
> filter, sticky parts inside pressure switch, etc.).  If running through
> those checks doesn’t solve the problem, I’d assume that wear is making it
> hard/impossible to reach 135#.  Then adjust it down to about 120# cut-out
> pressure.  Run it that way and let the heirs decide on final disposition.
>
> Back to your original question,  take the cover off the switch (1 or 2
> screws hold it).  Look inside.  Instructions for setting the pressure are
> often on a sticker on the cover or molded directly into the cover.  There
> are usually 2 adjustments.  One is the cut-out pressure (or maybe cut-in)
> while the other is often a setting for the DIFFERENCE between cut-in and
> cut-out.  Keep track of how much you turn them.  If things get worse, you
> will know how far to turn things to get back to where you started.
>
> Jim Becker
>
> *From:* deanvp at att.net
> *Sent:* Monday, December 06, 2021 10:57 PM
> *To:* 'Antique Tractor Email Discussion Group'
> *Subject:* [AT] Air compressor failure
>
>
>
>
> Need some help relative to a Husky 60 gallon , 7 HP air compressor.  I am
> shop sitting the shop in AZ of my recently deceased friend until his three
> sons can decide what they are going to do with the 10 tractors, 5 highly
> modified garden tractors and a fully stocked shop with a huge quantity of
> hand tools.  In return for doing the shop sitting I get to use the shop to
> do the work on my 1935 JD B and JD Garden Tractor.  Upon the very first
> entry I noticed the air compressor was running too long. I shut the breaker
> off and am not trying to figure out of there is something I can do to fix
> it. My first thought is the pressure switch isn’t working right.   But….
> I have never worked on this version. Attached is the picture of the air
> compressor. I have not yet found a operators manual or service manual to
> guide me through some trouble shooting.  I am pretty sure this was working
> at least up to the end of August and then my friend got confined to the
> house due to illness  and eventually died October 6.   I arrived in the
> middle of November to take first use of the shop again.  So the compressor
> sat unused for at least  couple months which may have something to do with
> it not working now.  It does pump up to 135 lbs pressure but does not shut
> off.  I set my compressor at home to shit off at 120 PSI.   So 135PSI seems
> high to me.   If I open the pressure switch is there some adjustments in
> there or is it maybe just stuck that needs to be unstuck?    Anyone with
> experience with this brand of air compressor?  I don’t want to create more
> expense because I don’t know what I am doing.   Here is a picture. Note:
> The red dial on top of the pressure control does work in that it shuts down
> the compressor when moved to the Off position. When moved to the Auto
> position it just continues running.
>
>
>
> Dean VP
>
> Snohomish, WA 98290
>
> "Socialism is a philosophy of failure, the creed of ignorance, and gospel
> of envy, its inherent virtue is the equal sharing of misery."
>
> ..Winston Churchill...
>
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