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Checking and Replacing Motor Brushes

Checking the Motor Brush in Central Vacuums (each motor has two)
(We highly recommend professionals do this.)
Motor can run. With the vacuum motor running and visible, you will want to be able to see the commutator (the top part of the armature) spinning and the motor brushes that are up against it. It is normal for there to be a slight blue spark right at the carbon brush - but if the blue spark is large and wraps around the commutator then you will need to replace the carbon brushes (if the commutator on the armature is seriously damaged, you will need to replace the motor). The most common cause of excessive sparking is an old motor that is beginning to fail. The armature is blackened, pitted, and scared with build up. The brushes may still have life (are longer than 3/16 inch) but the armature, sometimes spurred on by a not-so-tight bearing, is being damaged. It is true that the motor may just need new brushes if one or both are less than 3/16 inch long (the black carbon is 3/4 inches long when new) and the armature is pretty much completely smooth and the bearing solid. Get help removing the brushes for length inspection below.

Motor cannot run. If the motor is not running (many times a motor goes bad in the way a car runs out of gas) a couple of things may have happened. First, the motor brushes may have just been worn out and can no longer conduct electricity. Check to make sure the armature is not scored or grooved. If it is, replace the motor. If not, replace the brushes - it may save you big bucks if that solves the problem. Secondly, and most frequently, when the brushes are worn, they damage the armature. At around 19,000 RPM, this ruins the bearings and the motor is shot. You will need to replace the motor. ALSO, when a motor goes bad the minibreaker(s), at times, is compromised. When you replace a motor and the minibreaker pops, most likely that is the reason and you will have to replace the minibreaker(s). The minibreakers we sell are universal; simply choose a minibreaker that has at least the amps of the one you are replacing (for example, if replacing a 13 amp, buy a 15 amp, not a 10 amp).
Accessing and Replacing the Motor Brushes

The typical length of the carbon on new brushes is 3/4 inches. When it gets down to 3/16 inches, the brush assembly should be replaced. But if the armature is pitted or the bearing is wobbly, then replace the motor. Motors are made to be replaced after 800-900 hours of use.

  1. Get access to the motor. (You don't have to remove the motor)

  2. Accessing the Motor Brushes within ANY Central Vacuum Motor

    On motors that have a black, plastic, pop-off top without screws, such as 116336, 119413, 119412, 117939, 116765, 116296, 117944, 116764, 116945, 117123, 116472, or 116355, remove this black cooling fan cover to expose the screws that hold the motor brushes down. (The cover pops right off). Note that sometimes there may be channels directly to the screw head so the top will not have to come off to gain access.

    On the 115330, 115334, 115519, 115684, 116119, and 116136, motor you would remove the small screw in the sheet metal cover around the exterior circumference of the armature region. This will expose the brushes and the two screws that hold them down. Since the screws are located under the top shield, you can either use a small socket or angle your screwdriver to remove the screws that hold the brushes down.

    Often these screws are very tight and the procedure will require a sharp-ended screwdriver and quite a bit of force. In the worst-case scenario you may need to remove the top cover of the motor with two long bolts that secure it through the field stack. If you remove these, make sure you put the stack back in the exact same position because its angle is what determines the speed of the motor. You can actually advance the motor speed by rotating this field.

    On the Premier motor (and plastic versions of it), such as 116465, 117465, 116507, 117507, 117157, 117743, 117478, 117572, 117500, or 117502, you will not need to remove any screws to release the motor brushes. First remove a retainer clip on the top of the motor by prying it up with a flat head screwdriver and then the motor brushes will pop right out the side of the motor.

    Some motor brushes are held in with a clip that you have to bend out of the way.Bend the clip out and then up to access the brush. Bend the clip back into position before putting the plastic cover back on. These pictures show these steps:

  3. Lift out the motor brush and note the amount of wear. The black lead looking part of the motor brushes are one inch long when they are brand new. If you are performing MD's mandatory 3-year check and the motor brushes are more than 1/2 worn, you should replace them. If the black lead is 1/4 inch, you must replace them. The entire brush unit is replaced, not just the lead part and metal housing.

  4. When replacing, remove the flag terminal from the stud on the motor brush. Older motor brushes did not have a flag terminal but had a flat spade that slid between the motor brush casing and the metal holder. To remove this type of connector, crush the outside housing of the motor brush with a pair of pliers. You can then insert this spade into the same location on the new motor brush and ignore the male flag stud on the new motor brush.

  5. Replace the brush back into the slot and be sure that it's metal housing does not make contact with the armature. Screw down the two screws on each of the motor brush bracket holders (if neccessary).

  6. Motor brushes will properly seat themselves to the curvature of the commutator armature. Some may prefer to seat them running the motor at half voltage for 30 minutes using a variac or other voltage control device. While seating, be sure a vacuum inlet door is open or hose is plugged in so air is flowing through the unit preventing over heating.