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Sanborn Air Compressor Bogs Down and Runs Slow

Published Categorized as Air Compressor Runs Slow Bogs Down, Sanborn 2 Comments on Sanborn Air Compressor Bogs Down and Runs Slow

If your Sanborn air compressor is bogging down, and you can’t quite figure out what the reason is, it can be very frustrating. Fortunately, this guide will provide you with the most common reasons why your Sanborn air compressor bogs down, along with existing reader questions and responses.

Table of Contents

3 Most Common Reasons Why Sanborn Air Compressor Bogging Down

Diagnosis of the problem may not always be so easy as there can be many things that can be the cause of the Sanborn compressor bogging down. However, here are some of the most common reasons why your Sanborn air compressor bogs down:

  1. The use of a too-small extension cord or power bar to power the compressor – if an extension cord or power bar is being used, remove it, and plug the air compressor power cord directly into the wall socket to see if that helps.
  2. Too many other power-drawing appliances on the same circuit as the feed to the compressor – ideally, an air compressor should be powered from a socket that leads directly back to a 15 amp (minimum) or a 20 amp breaker or fuse at the panel. If other appliances are in the line that feeds the compressor, shut them all down, and test the compressor again.
  3. The compressor unloader valve has failed – to test this, open the tank drain and let all of the air out of the tank. This will emulate the unloader valve function, and at the same time, remove any water buildup inside the tank. Close the drain and power up the compressor to test. If the compressor starts easily and runs up to cut out pressure, it is time to service or replace the unloader valve.

For more detailed information on this topic, visit our Air Compressor Bogs Down – Solutions & Diagnosing Problems guide!

Reader Questions & Responses

Sanborn Air Compressor Bogs Down and Runs Slow – Sanborn Air Compressor Troubleshooting


I just bought a Sanborn air compressor 3 hp Magna Force. It looks to be rather new.

Sanborn 3 Hp Magna Force Air Compressor
Sanborn 3 Hp Magna Force Air Compressor

When I turn it on it starts pumping but quickly slows way down and quits running before it gets to 30 lbs of pressure.

I took the belt off the motor and turned it on and the motor runs fine. When I put the belt back on the same thing happens again.

Any ideas on what’s going on with this compressor?



Tom, what is the voltage of the Sanborn air compressor motor, please describe how you are getting power to it. In other words, are you using an extension cord or power bar?

Questioner #2

My model #112A300-30N. does the same thing. You first turn it on it runs fine but after a few seconds it pulls down and then shuts off (before the tank is anywhere close to full) I think it may be a pressure switch, but I’m no expert.


I doubt if it is the pressure switch.

Typically this issue is created by a couple of things. Either the motor cannot overcome the increasing load of a mechanical issue in the pump, or, the motor isn’t getting enough power from the source or through the run capacitor.

That’s why I asked the original poster if they were using an extension cord. Often a too small cord is the reason the motor lugs down when pressure builds.


Sounds like the motor could be wired to run on 220V but the has a 120V plug. that would make the motor run as you describe.

check the schematic inside the cover of the Junction box on the motor to make sure it is wired correctly for your electric supply.

If you have any questions regarding a Sanborn air compressor bogging down, please leave a comment below, with a photo if applicable, so that someone can help you!

By Bill Wade

About Air Compressors has been helping folks with their Air Compressor Problems since 2002 online. We're a community of DIY and Compressed Air professionals who are keen to support everyone across the globe with their air compressor issues and troubleshooting. Whether you're trying to identify an old air compressor, or troubleshoot an error code on a sophisticated new industrial air compressor - the community at About-Air-Compressors.com is here to help you

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