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My Floor Buffer Trips Circuit Breakers...

I see this issue literally every day and it's about time I blog about it on our website. This page happens to be one of our top 10 most viewed, so I know many of you have this problem.  I can't tell you how many times customers have purchased a new $800 motor on line and we call asking, "Do you really need a motor?  What's wrong with the old one?" and we find out a $50 part is all they need.

The typical problem I hear is "As soon as I pull the trigger, the wall circuit breaker trips…" or "When I pull the trigger the unit doesn't start fast and doesn't have any power…"  

If the unit is a high speed burnisher, or low speed high torque unit, then the problem is a rectifier located in the top of the motor.  ALL burnishers of 1000 RPM or more are AC motors at the wall, but convert the AC current to DC electrical power inside/near the motor.  Why use a DC motor?  Simple, they deliver more torque to turn the pad.  If you don’t have a DC motor, jump to the AC motor section….

If the unit immediately trips a circuit breaker, the rectifier has blown a short.  If the motor starts, but has no power then one half of the rectifier bridge has blown.  You can purchase a replacement rectifier and view the part by clicking here.  Our part comes complete with an upgraded rectifier and the very important thermal transfer compound required for installation; you will also save money.  OEM parts do NOT come with the compound.

Where is it located?  Typically inside the motor itself.  RARELY do you have to disassemble the motor itself.  Some older models located the rectifier on the base of the buffer external to the motor.  You may have to remove housing cover(s) to reveal the part.

When changing the part, you must align the new part in the same orientation as the old part with the notched corner in the same position.  Change only one wire at a time, if you fail to connect them correctly you will damage the motor.  The next step is CRITICAL -- before you install the new part, use the thermal transfer compound provided with our part exclusively.  The compound looks a lot like and has the same consistency as toothpaste.  On the back bare metal side of the rectifier, place a “pea” sized amount of compound, then reattach the rectifier to the mounting point.  Do not over tighten the screw.  FAILURE TO USE THE HEAT COMPOUND WILL CAUSE PREMATURE FAILURE OF THE PART.  Reassemble everything and you’ll be buffing again.

I get asked why this might have blown?  There are many reasons why that influence the failure, but it boils down to heat.  Using the machine on extension cords, bearing down on the machine, things that increase the electrical load on the machine will cause the rectifier to deliver more power to the motor increasing the heat inside the part.  If the heat cannot be displaced fast enough, the part will degrade and eventually fail prematurely.  If you are replacing this part a lot, then look at how you are using the machine.  When I review this with customers, it always ends up being the simple things.  For example, they added an extension cord (which starves the motor and causes higher amp loads NEVER do this without the PROPER gauge extension cord), they are pushing too hard on the pad (lowering RPM, cooling, and creating a much higher electrical load), or even poor maintenance (broken plug, or cutting too many wires when replacing the plug, electrical breaks on some percentage of the wires inside the cord - a difficult problem to find).  If your power cord gets hot, or more than just warm, you have an electrical issue to address.  Look for burnt insulation on wires in the handle, burnt or melted crimp connectors, etc.  A specific hot spot in the middle of your power cord it telling you "I'm busted right here"  -- it is time to install a new power cord regardless of physical appearance of the outer covering.
And this should be obvious, but I'll say it here.... If the motor was dropped, fell down the stairs, or off a dock, don't expect this to solve your problem.  The motor should be serviced by a trained electrical motor technician.


These motors are more difficult to locate the source of the problem.  AC motors will ALWAYS have capacitors on them to assist in starting and running.  Some motors have one start, and others have two depending on the design of the motor.  Most AC motors have a start switch that operates on the turning of the armature.  This switch is under the motor's cover on top of the armature.  To replace it you will need to disassemble the motor.  The typical symptom of this switch stuck is pulling the trigger, the motor humming or turning slowly, the lights dimming, and then the breaker tripping.  The contact points can sometimes be cleaned in a pinch with high grit sand paper, but the switch contacts arc when they operate and will eventually degrade, the switch must be replaced.

There are often different combinations of carbon brushes in the motors.  It is important to inspect them and the contact areas, if you see any damage the parts must be replaced.  They are easy to replace and will extend the life of the motor dramatically.