Compressor after storage?

Kram · 2026-03-30T21:37:09+0100

Compressor has been buried behind other tools for nearly 4 years in a dry shed without any use. I got it in 2017, so 9 years old.
In total its had very few hours of use, its still on the original oil - perhaps time to change it..?

Turned it on today, first issue is it did not appear to cut off or, went slightly into the red part of the gauge and I stopped it just in case.
The pressure relief valve felt stiff and wasnt easy to manually pull, and stuck out. After a few pulls it seems to be moving freely like it should. Should I apply some lubricating oil to the PRV?
Any other maintence to do?
The tank was always drained before storage, so rust should not be a problem.

I'm a bit fearful of letting it run up to full pressure in case it doesnt want to cut out and the PRV failing to open.

I'll watch it closer when I try it tomorrow!

Erie Fred · 2026-03-30T21:45:10+0100

Back the pressure switch down a few pounds.
Sounds like it's a bit sticky, and cranking it a few turns lower should get
things moving again.

Bouledogue · 2026-03-30T21:55:35+0100

As Fred says.

Or, if that doesn't sort it, - assuming of course it isn't one of the posh jobbies - the pressure switches are cheap as chips to buy on the interweb.

Kram · 2026-03-30T22:30:05+0100

Thanks I've never touched the pressure switch before, I'd be much happier if it stopped a bit earlier, appears simple enough, loosen the sprung screw. I'll try tomorrow and carefully supervise it.

Dapph2 · 2026-03-30T23:08:15+0100

Give the switch if it is a ring pull type, a squirt of WD 40 and wiggle it about whilst the compressor is running . It could just be a stuck seal. Now open the air valve ( not the air tank drain ) and operate the compressor for 30 seconds or so , so you get a trace of oil in the out going air outlet .

Then close it & once the pressure gets to red turn the compressor off , do this a few times , each time when the tank is full draining via the air tank drain cock .

roofman · 2026-03-31T06:57:14+0100

Could be the copper contacts in the switch box are stuck...funny enough i have just orded a new switch myself from the bay of pigs...£10 not even worth trying to fix at that sort of money.

RichardM · 2026-03-31T08:01:09+0100

If it's going onto the red I would have expected the pressure switch to operate before the prv.
Best check both.
Of course it may also be the pressure guage that is faulty.