Fixing An Air Pressure Regulator

Fixing an air regulator offers it’s own challenges, for sure. I am very happy to extend from all of us thanks to Ed Parks for these instructions on fixing an air regulator.

It is very kind of him to take the time to put this down and send it to me for inclusion on this site. Here are Ed’s instructions.

If you’re trying to fix your air compressor, or you’re wondering how to fix an air compressor problem that you’re having – check out my air compressor troubleshooting page for a detailed list of common air compressor problems and links to handy guides on how to solve your air compressor problems!

Step by Step Guide to Fix An Air Pressure Regulator

Step-by-Step Instructions to Repair Air Compressor with a faulty regulator that does not allow adequate air pressure to come out of air hose.

  1. When (the compressor) tank has plenty of air but you only get a short burst of air pressure (only momentarily) out of air hose and compressor’s air hose gauge goes to zero.
Fixing An Air Regulator The Tools Required To Fix Air Regulator
Fixing An Air Regulator The Tools Required To Fix Air Regulator

2. Be sure tank is not empty and has some pressure in tank. Turn Regulator Control Knob counter-clockwise all the way and release all pressure from air hose connector. The air pressure in the tank forces the Control Knob’s plastic piston to move back into the Control Knob/Regulator’s housing thus preventing damage to the plastic piston when disassembling.

3. Make sure compressor is unplugged.

4. Now release all air pressure from tank using the water drain valve on bottom of tank.

6-screws-to-remove when fixing an air regulator
5. Remove (6) screws holding top half of plastic compressor cover on: (2) from handle and (1) at each corner of plastic housing cover. The (2) screws in the handle are Machine Screws 10-32 x 1″ Phillips and most likely will strip when reassembled – replace with 10-32 x 1 1/4″ Phillips.
under-the-compressor-shroud when fixing an air regulator
6. Lay top half of plastic cover over to side – no need to disconnect any wires.

7. Remove Regulator by using Crescent Wrench and turning hex nut counter-clockwise. Will be tight but be gentle so as not to damage o-ring seal. There will be just enough room to get wrench on at an angle with bottom plastic housing still in place when the Control Knob is completely screwed out.

remove regulator-hex-nut when fixing an air regulator
Remove Regulator by using Crescent Wrench and turning hex nut counter-clockwise.

8. Regulator Control Knob removed.

Regulator Control Knob removed

9. Turn the red Control Knob clockwise and the plastic piston with post in the middle (in above picture 5) will be pushed out.

10. Remove plastic piston, compression spring, and metal disk from Control Knob housing and clean all parts with a paper towel or rag; don’t use anything in housing that will scratch inner wall of cylinder, but clean out any corrosion. Do not remove the (2) o-rings from the plastic piston unless you plan to replace them.

11. Turn red Control Knob counter-clockwise again to screw knob out for reassembling.

12. Apply a thin film of lubricant (would not recommend grease as it will gum up with time) – Teflon or Silicon lubricant or o-ring grease to the cylinder walls of the control knob’s housing, to the metal disk, and to the o-rings.

13. Reassemble the above parts. Be sure the metal disk’s cupped side is facing to the bottom / inside of the Control Knob. It is easier to get these parts reassembled if you hold the parts as pictured below (on the crescent wrench) in your hand and place the Control Knob on top of them pressing them into the Control Knob housing carefully, not to damage the o-rings. Press in until completely seated like in picture 5. Sit reassembled Control Knob aside until final assembly.

Reassemble the above regulator parts.

14. With a large flat screwdriver unscrew brass tank pressure seal assembly. Do not remove o-ring unless you plan on replacing it.

Clean inside of compressor manifold

15. Clean inside of manifold with a paper towel or rag.

The regulator Tank Pressure Seat.

16. The part causing the problem is the rubber Tank Pressure Seat. Carefully remove the spring with it’s rubber seat, clean both parts. What has happened, due to the type of material, from pressure and moisture the rubber has swelled to the extent that an adequate amount of air cannot pass around the sides of the rubber seat. No need to remove the rubber seat from the compression spring.

Regulator rubber seat from the compression spring

17. Using a Dremel with a 1/8″ round carbide bit carefully grind a notch into the (4) sides (the center of the sides only, not the corners) of the rubber seat. BE VERY CAREFUL NOT TO GRIND TO DEEP.

Upon close inspection of the sealing surface of the rubber seat you’ll notice a circular groove that makes contact with the sealing / mating surface inside of the brass threaded hex bushing. Be sure to not grind any where close to this sealing groove in the rubber or your tank will no longer hold pressure when stored. Do Not Grind on the corners at all; the corners keep the rubber seat in place and aligned in the brass hex bushing.

Disassembled regulator and spring

18. Notice depth of the notches is just enough to create a gap for air to come around the rubber when it is reassembled in the brass threaded hex bushing.

Notice depth of the notches in the regulator seal

19. Apply a very thin film of Teflon or Silicon lube or o-ring grease to the rubber and reassembly into brass threaded hex bushing.

Grooves in regulator seal

20. Apply a light coating of lubricant to the o-ring and screw brass assembly into manifold. Just tighten snugly – no need to overly tighten o-ring seals -, just good and snug (to tight will cut o-ring).

21. Apply a coating of lubricant to the Regulator Control Knob assembly’s o-ring and also to it’s mating surface of the manifold. This o-ring will be fairly easy to cut if not careful. Reassemble Regulator Control Knob assembly into manifold, again tighten snugly, but don’t over do.

22. Reassemble top half of plastic cover to compressor.

This fix will now allow an adequate amount of air to pass around the rubber seat that had swelled over time.

If someone can locate a part number and a source for a new rubber seat please post it on the parts needed page, and refer to this page too, if you would.

Dave comments

Thank you so much for your repair instructions about how to fix a regulator on the page Now my Central Pneumatic 3-gallon pancake air compressor, model 95275, from Harbor Freight is working again. Yippee! I didn’t have the proper lubricant, so all I did was disassemble it, and used my Dremel to shave off bits of the rubber Tank Pressure Seat, as you showed. I wasn’t sure what you meant about the “corners”, since it was perfectly round, but I just shaved off a little from the four points of a cross, reassembled it, and now it releases air again. Before, it would only do one brief puff of air, and then the regulator pressure gauge would bottom out at zero, and have no more pressure, even though the tank was fully pressurized.

Note added: I didn’t have a screwdriver big enough to remove the Tank Pressure Seal, but a socket wrench worked very well. Putting it together, I just needed to push down on the head of the Tank Pressure Seal to compress the spring and start threading it in a little by hand, and then I could use the socket wrench to tighten it the rest of the way.

Fixed now, thanks to you! You have a very informative site, and I greatly appreciate your work.


Response: Well Dave, the originator of these instructions was Ed Parks, and we would very much like to send him your comment but have no way of reaching him. I hope he reads your kind words. Cheers!

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