View Full Version : Air Compressor fails to shut off

12-03-2012, 08:29 AM
bought a new "returned" cheapo Pal 60 gallon air compressor and replaced the pressure switch from original (Auto/Off switch failed plastic junk) Thus the reason for return. Price was also 75% off.
Now after replacing pressure switch the compressor does not shut off. It's fine building to 100psi then struggles to get to 120psi then sits at 120psi. The extra air is ejecting out of one the 3 cylinders as the filter cover is Hot and screaming air noise from it.
if i turn the pressure switch to OFF then On again the compressor stays off and holds the 120 psi, no Air leaks from tank or cyclinder.
Back in "Auto" once i start using air and it kicks in to recharge, again it goes to 120 then ejects out of same cyclinder. The pressure switch does not engage as I'm suspecting it shut off value is a little higher.
Is this a resolvable problem?
Is the problem the Air Cyclinder?
*Note When I ran the system with faulty pressure switch the unit shut off at 125-130 psi tested 3 times before replacing.

12-03-2012, 09:47 AM
The failure to shut off is either a faulty switch or one that just needs it's shutoff pressure adjusted.

The air leak is probably the high pressure relief valve. Once the shutoff point is set below that value it will likely be OK.

Do you have the instructions that came with the new switch? If not post a picture of the switch with the cover off.

12-03-2012, 10:12 AM
I tried to Google "Pal 60 gallon air compressor" and could not find a thing. 3 cylinder el cheapo?

Jim Johnstone
12-03-2012, 10:48 AM
I tried to Google "Pal 60 gallon air compressor" and could not find a thing. 3 cylinder el cheapo?

Yep, PAL is Princess Auto Limited. Canada's Harbour Freight.

Sounds like you need the pump rebuilt, or at least a gasket replaced.

12-03-2012, 11:02 AM
Ah, thanks. The 3 cyl part with on bleeding struck me as odd. But, compressors do reach a limit where they can't build any more pressure. I usually drop mine to a lower pressure than factory set and they run less and build faster. I don't know why I would need more than 110 lb.s static pressure. If I do, I need more compressor volume, not more pressure. I can't think of one tool that has to operate at over 100 lbs continuously.

Maybe some need that for a large impact or possibly a die grinder. But, I digress.

+1 on lowering the pressure cut off.

12-03-2012, 01:10 PM
I'll take the suggestion to drop the cutoff point to 100-110. Main usage is for plasma cutter @ 75psi with flow @ 6.7 cfm.

From comments given> air blow back was not releasing from pressure relief valve. It is comming out one cyclinder (air intake) Thats why the cover is so Hot and the other two are cool and no noise.
It sounds like its fighting Air in Air out Thus the high pitch air sound and i can feel the air coming out and going in. (cigarette test :) )
So the the Pump screwed? just a gasket?

Unit is from Princess Auto and under warranty.

12-03-2012, 02:34 PM
That sounds like a broken intake reed valve.

12-03-2012, 02:50 PM
Princess Auto is very good on warrenty issues . Talk to them .You might get a new pump out of the deal .

12-03-2012, 03:50 PM
I think a may have assumed wrongly. I thought air was leaking from the one cylinder only after 120 psi or so was reached. If that's the case, my original post is still valid. But if it leaks all the time, likeln a broken reed valve.

12-04-2012, 12:12 AM
I checked with store rep before seeing your reply and he also said it could be sticking reed valve. I dumped the air and restarted. I do hear the suspect cylinder blowing back while building up starting around 50 psi, faint but there. Much noticeable beyond 70 psi.
Took the head off and reed valve looks visually ok to me that is. I'll take the head back to store and see what they will do, as rep stated he may give me another pump or return whole thing.
Figures just after i finished installing all my pipe lines and anchoring it down to cement floor.
I'll post a final result when i get news of its fate.

Bob C
12-04-2012, 05:20 AM
Not the high pressure relief. It is most definitly a gasket/valve issue.

12-05-2012, 09:07 PM
top side of the head looked like it has heat scorch marks from piston overheating or not getting enough oil. They will replace the whole pump for free as they had other units with same problems within same time frame. LOL just saw a returned unit same as mine at store for sale without pump! Bad crop from night shift line :)