Thanks for the post!

This is a solid unit, and it should take little to tune it up so it runs well. We recommend straight 30-weight air compressor oil, or a synthetic or synthetic blend air compressor oil. All air compressor oil is NON-detergent, which is necessary.
You can find air compressor oils on our site by clicking the below link:

www.mastertoolrepair.com/synthetic-synth...essor-oil-p-733.html

You can also view the parts schematic and parts list for this compressor on our site by clicking the below link:

www.mastertoolrepair.com/air-compressor-...-25-m165-p-1934.html

I would simply make sure the air filter is clean (or replace if missing), make sure the belt is aligned on the pulley and flywheel, which no more than 1/2" of deflection when you press down on it.

Hopefully the valves are in good shape and aren't rusted. You can remove the Belt and the main Supply (Discharge) Tube and turn the pump flywheel by hand to confirm it has compression; you should be able to feel resistance, of course (as it compresses and goes through its stroke), but you should certainly be able to turn it by hand.

If all is well and you have no leaks and no moisture in the tank, then you're good to go!

Feel free to reply with any additional questions or concerns.

- MTR

You can certainly upload a photo or video if you would like.

Just click "Reply" (not "Quick Reply") and below the area where you would type your reply you will see "Attachments". Just click "Add File" and you can choose any number of files to attach.

- MTR

That's the on/off Pressure Switch that you need. It's the electrical/pneumatic "brain" of the compressor that controls the cut on and cut off PSI of the unit. It's what the motor and power cords are wired to.

This unit had a couple of different set-ups, can you upload a photo of your compressor, and the pressure switch?

You can view one style by clicking on the below link:

www.mastertoolrepair.com/air-compressor-...-25-m165-p-1934.html

...and the other style is located below:

www.mastertoolrepair.com/regulator-parts...-104b200-p-3197.html

Which set-up does your most resemble? This will nail down the pressure switch you need. Also, there is an OEM part# on the pressure switch starting with "034-xxxx", it should look something like "034-0097". This should be on a white sticker either on the cast manifold, right below where the wiring goes into the switch, or inside the black plastic pressure switch cover.

- MTR