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How to fix/replace air-pressure regulator on old Sears compressor

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Forum topic by Sark posted 06-26-2019 06:21 PM 892 views 0 times favorited 12 replies Add to Favorites Watch
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Sark

138 posts in 782 days


06-26-2019 06:21 PM

Topic tags/keywords: compressor repair sears compressor

The air-pressure regulator on my old Sears compressor is failing. Won’t allow pressure over 90 PSI and the air pressure cannot be dialed down much. Unable to find direct replacement parts. Neither Sears or other retailers can even find the model let alone replacement parts.

The compressor itself is a 3 HP oil bath compressor 240 v. I’m guessing the compressor is 20+ years old, and runs fine. The black knob controls the pressure and sticks out about 3” from the manifold. Any ideas on how to go about fixing or some work around? Thanks.


12 replies so far

View Fred Hargis's profile

Fred Hargis

5595 posts in 2915 days


#1 posted 06-26-2019 06:30 PM

I’m pretty sure you can buy after market replacement switches, that would be where I would start.

-- Our village hasn't lost it's idiot, he was elected to congress.

View LesB's profile

LesB

2131 posts in 3865 days


#2 posted 06-26-2019 07:25 PM

There are numerous sources of new compressor “control switches” in addition to which you can easily add a pressure regulator to control the pressure to the air hose. It may just take a little creative plumbing and electrical work to connect every thing up. Some control switches come with a regulator included. Be sure to include a pressure relief valve in the mix. Here is one “sample”. https://www.tptools.com/Air-Compressor-Pressure-Control-Switch-3-5-HP,6420.html

With a compressor that old I would also be concerned about the integrity of the tank.

-- Les B, Oregon

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Sark

138 posts in 782 days


#3 posted 06-26-2019 07:50 PM

Thanks for the tip. I never thought of the pressure-regulator system as a switch, but of course it must be because it switches the compressor on and off.

The Sears model has an adjustable regulator so you can adjust the pressure down to 40 pounds, for example, if you want to run low pressure for some reason. Don’t use it much, but occasionally its useful, like if I’m driving staples into thin material.

I’ll look around some more. Pressure relief valve sounds like a reasonable add-on. I have no way of checking the integrity of the tank, but it’s not leaking, which I think would be the first sign of problems.

View ibewjon's profile

ibewjon

684 posts in 3215 days


#4 posted 06-26-2019 08:02 PM

How often do you drain the tank? I have seen tanks that have exploded due to internal corrosion or rust that can not be seen from the outside. Wish I had a picture. You should be able to do a pressure switch with cylinder bleed down for easy restart, and a separate regulator. Relief valves are $20 or less. But at that age, look at the price of the parts vs new compressor with a new tank. Tap on the bottom of the tank with a wood block or small wrench, looking for different sounds. Might find a thin spot, then scrap it.

View CarlosInTheSticks's profile

CarlosInTheSticks

413 posts in 794 days


#5 posted 06-26-2019 08:24 PM

It is possible the diaphragm or spring are damaged or the ports are dirty, regulators are made to be repaired, take it apart and have a look it, may just be dirty. Compressor switches have a high and low setting one to turn the compressor on and the other to shut it off, they are not designed for regulation and come set from the manufacturer, they can be adjusted, but it is not recommended. Your regulator is installed on the output from the tank, where a replacement should be installed. The compressor already has a relief valve (also known as a safety valve), it would be a chargeable offense if the manufacturer sold you a compressor without one. The relief opens if your compressor switch fails to shut the compressor down at the set pressure, to avoid blowing up the tank. If your compressor is operated properly it will last a life time. If you neglect oil changes and filter changes and fail to drain moisture out of the tank after use, it won’t last long.

-- "There are no utopias, chaos theory reigns, anyone who says different is selling you something"

View PaulDoug's profile

PaulDoug

2007 posts in 2125 days


#6 posted 06-26-2019 11:54 PM

Check Youtube, may have a video with the exact repair you need….. I always check Youtube.

-- “We all die. The goal isn't to live forever; the goal is to create something that will.” - Chuck Palahniuk

View Sark's profile

Sark

138 posts in 782 days


#7 posted 06-26-2019 11:58 PM

The compressor goes on and off and the tank pressure shows about 110 pounds to 120 when fully charged. So I’m guessing that the switch itself is working OK. The outlet pressure is adjusted by a handle/black knob as shown in the picture. Nothing really happens when I turn the handle to adjust the outlet pressure. So I like the idea of taking it apart and looking. Will report back after doing this.

So how worn out is the tank? I’ll try the tap test and see if I find something out. I do have an alternative unit, almost identical except its listed as a 4 HP unit, which is odd, since the 3 HP and the 4 HP have the same motor rating. Marketing. As far as regular maintenance is concerned…I’d say irregular maintenance. Maybe goes a year or two between draining. I ran a cabinet shop for a dozen years…and this home unit didn’t get used much. But now its back in service…and I like my tools to be working. And safe

View ibewjon's profile

ibewjon

684 posts in 3215 days


#8 posted 06-27-2019 12:49 AM

Just buy a new in line regulator, leaving the old one in place. Put it in the output after the tank.

View Dark_Lightning's profile

Dark_Lightning

3469 posts in 3531 days


#9 posted 06-27-2019 12:57 AM

The less a compressor is used, the more likely that the tank will be rusty, especially if it wasn’t drained regularly. Most places I worked, we drained the tank daily. We just let it run out when we went home for the night. I couldn’t tell you whether that tank is safe or not. If it were mine, I’d at least try to inspect the inside, or just scrap it. The compressor I have now is about 20 years old, and I’m looking at just tossing it, for the simple reason that I’ve only drained it maybe 10 times in all those years. I’m guilty of it, too!

-- Random Orbital Nailer

View CarlosInTheSticks's profile

CarlosInTheSticks

413 posts in 794 days


#10 posted 06-27-2019 01:00 AM

Sark you were not clear and this may be a silly assumption but after adjusting the regulator did you open the outlet discharge valve and then close it to reset the outlet press. If you don’t do this you will not see any change in the gauges.

-- "There are no utopias, chaos theory reigns, anyone who says different is selling you something"

View Sark's profile

Sark

138 posts in 782 days


#11 posted 06-27-2019 02:51 PM

Thanks for the replies. I beginning to think its time to scrap the old air compressor. I have a couple of smaller ones to use while I shop for a suitable replacement. I looked at the Youtube video of a compressor exploding, And I also read the very interesting comments on the probably cause of the catastrophic failure. All seems very unlikely.

Back in my poorer days, I simply couldn’t afford to toss a working tool. Tools got trashed when they failed. However, I’m putting a new compressor on the buy list, based on your comments, and also based my frustration with spending time on keeping the old machine going…pulleys out of alignment, pressure gauge failure.

PS Carlos, not a silly assumption, maybe its been working all along. I’ll give it a try.

View Sark's profile

Sark

138 posts in 782 days


#12 posted 06-30-2019 12:51 AM

While fiddling with the compressor, I noticed a serial number with date on the tank: 1979. That would make it 40 years old, so that pretty much settles that question. Time to replace. I have another Sears compressor dated about 1988 so that’s a mere 30 years old. Back when Sears made relatively high quality items for the small shop. Think I’ll replace them both.

The question is: Sell, trash or give away?

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