Air Pressure adjustment on compressor

Hi all, I have a Puma upright 220/240v compressor that is rated at 150 psi max. It currently is shutting off at 90 psi and always has since new. I recently got a used tire changing machine and realized that 90 psi is a little low so wanted to increase to 120 or so but when I read the owner"s manual and went on their website it looks like they "preset" the pressure and don"t tell anyone how to reset. I have attached a picture of the pressure control and the two screws (red arrows) that I "think" would control the setting but wanted to ask some opinions before I starting messing with it...can anyone help?
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Usually there are instructions inside the cover, that's a different switch than I am familiar with. Make sure you have a working safety pressure relief valve before you crank it up!
 
There should be a brand name and model # on the pressure switch. Should be able to find the info doing a search.

If not, one screw will be the pressure, the other will be the differential.

With the tank pumped up to 90, start turning one in, count the turns so you can put it back. It should come on within 2 turns. If not, put it back and try the other. Once you determine which is the pressure screw and which is the differential, you can fine tune it through a few cycles.
 
Any of those switch covers I ever had off had the instructions inside the cover.
 
The picture isn't very clear but I think the screws you are pointing to isn't the adjustment screws. Any pressure switch I've worked on the screw to adjust the pressure has a heavy duty spring under it.
 
"the screws you are pointing to isn't the adjustment screws. Any pressure switch I've worked on the screw to adjust the pressure has a heavy duty spring under it."

Stephen, you obviously haven't looked at/dealt with/adjusted pressure switches from "The Land of Almost Right"!

LOL!
 
Keep in mind that the rest of the compressor needs to be rated to handle the increased pressure. Check the working pressure on the tank. Also look at the relief valve setting. If it pops off at 100 psi or so, you will also need to reset that for a higher pressure. You may also have to get a higher rated pressure control. Grainger sells them, and they are not all that expensive.
 

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