Regulator knob won’t turn

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by Dave
(Florence, Mass)

I own a Bostitch 6-gallon compressor – reconditioned. Using it for the first time.

The regulator knob will not turn – not even a little. Seems really frozen – or something.

Bostitch air compressor
Bostitch air compressor

The compressor DOES work. I’ve nailed some things with it. Now I just want to regulate it. Ideas?

If pushing in or pulling out on the regulator knob doesn’t allow you to turn it to adjust the downstream air pressure, then I suspect you’ll be adding a new air regulator soon.

What pressure is showing on the regulator gauge? If the regulator is built in, and you are getting full pressure downstream from it, you can install a regulator at the end of the discharge coupler, and then put a coupler on the other side of it for the air line, and achieve the same results, as long as the first regulator is fully open.

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I have the same problem with Porter Cable cpl 6025. Regulator D27255 is no longer available. I removed the regulator knob from the compressor. I am able to pull back on the knob to unlock. Bot there is no movement either way. I then disassembled the knob to find a spring inside along with the metal shaft and plastic disc. The knob will turn with the spring, shaft and disc removed.But once the shaft is inserted,the knob will no longer turn. The hex shaped bottom of the shaft fits into hex shaped indentation in the knob which prevents any movement.… Read more »

Pix would have been nice… But I think what you’re missing the (possibly broken) piece on the knob that lifts the hex things apart. Or, the hex not part of the of the knob is frozen up. Probably the easier thing is just look for a four port regulator similar to that one, and plumb it in. You may have to re-arrange some stuff. Or, get a two or three port one and add plumbing to replace the extra ports. Likely that’s just a couple of tees and nipples. If you haven’t removed it yet, get some pix of it… Read more »

Thanks Doug for the prompt reply Sorry for not including these pictures. This 2004 compressor had the regulator d27255 changed in 2008 with the original part. Made in Taiwan. Used the compressor since then without any problems. If I turn the knob counter clockwise without pulling the knob out, it will unscrew from the housing. Maybe that is what I did and a part fell out that was located within the housing. I did find a spring (3 photos) in my parts tray but I believe it is a brake shoe hold down spring. When I separated the knob into… Read more »

control knob in place.JPG
regulator inside 1.JPG
inside 3.JPG
inside 1.JPG
spring 14 inch.JPG
spring 58 inch.JPG
spring 78 incn.JPG

Speaking of fails – How did you wear it out? Do you use it for ratchets and such as well as painting?
If so, I suggest you set the machine regulator at the highest pressure you use. If you need lower pressure for say painting, use a second regulator in series to get what you need for that. Double end quick connects.
(The gauge in the second one is not broken, it’s under pressure.)


Basically use it with Ingersol Rand torque wrench to remove and install wheel lugs and to inflate tires to 32psi
.Original lasted 4 years. Replacement lasted 14 years
Do not understand why it wore out
Pulling out the knob and turning clockwise or counter clockwise to adjust pressure.
What could have worn out inside the regulator?
Use the compressor only a few times per year.
Thanks and have a great day.

The threads on the knob. There is a lot of pressure on that spring, which is what adjusts the regulator output. I leave my system at full tank pressure and use filter/regulators to feed my stuff. Most everything uses 90 psi, and of course you can use that for tires too, if you’re reasonably careful.