Before you condemn an Ametek Lamb motor, pull it and look at the brushes. Carbon brush wear is the most common way these motors fail, and it is the cheapest thing about them to fix. This is the carbon brush assembly for Ametek Lamb universal vacuum and blower motors, supplied complete with lead and spring, and it corresponds to the Ametek number 33450-2, also listed as 833450-57.
The symptoms are recognizable. The motor runs weak, or it starts and quits, or it sparks visibly at the commutator. Repair techs on vacuum forums describe going through motors for years before discovering one brush worn to a nub and the other gone entirely, because nobody had ever checked. The replacement threshold is simple: change the brushes when the carbon is worn to about 3/16 inch. Waiting past that lets the spring and lead reach the commutator, and a scored commutator turns a cheap repair into a motor purchase.
One detail separates a long-lived repair from a short one: do not run brand-new brushes straight to full voltage. New carbon has not taken the curve of the commutator, so the contact patch is small and arcing pits the copper. Experienced techs bed brushes in at reduced voltage first, some using nothing more than a fan rheostat, and describe proper seating as the difference between a short motor life and a very long one.
A motor takes two brushes, so order accordingly. Documented fitment covers the Ametek Lamb 117478, 117500, 117549 and 117549-12. Wider dealer lists circulate for other 117400 and 117500 series variants, but the number on your motor tag is the only reliable check.
Built for
- A motor that runs weak, intermittently, or will not start with brushes worn short
- Preventive brush replacement during a scheduled motor service
- Rebuilding a motor in a machine where a full motor swap costs many times more
- Central vacuum power-unit service and extractor or blower shop work
Specifications
- Type: carbon commutator brush, supplied with lead and spring
- Ametek reference: 33450-2, also listed as 833450-57
- Documented fit: Ametek Lamb 117478, 117500, 117549, 117549-12
- Service threshold: replace when the carbon is worn to approximately 3/16 inch
- A motor requires two brushes
- Recommended practice: bed new brushes in at reduced voltage before full-load running
Frequently asked questions
How many do I need?
A universal motor uses two brushes, one per side. Always replace both at the same time so they wear evenly, and check the pair whenever a motor is out for any reason.
How do I know the brushes are the problem?
Look for a motor that runs weak, starts and quits, or sparks at the commutator. Pull the brushes and measure the carbon. At about 3/16 inch or less they are done. If the carbon is long and the commutator is clean, look elsewhere, most often at bearings or a restricted airflow path.
Will these fit my motor?
Documented fitment is the Ametek Lamb 117478, 117500, 117549 and 117549-12. Broader lists covering other 117400 and 117500 series motors circulate among dealers, but motor variants differ. Read the number on the motor tag and we will match it for you.
Should I just replace the whole motor instead?
Not if the only fault is worn brushes. Brushes are a small fraction of what a motor costs. Replace the motor when the commutator is scored, the bearings are shot, or a winding is open. Also check for a clogged bag or filter, since restricted airflow starves a motor of cooling and is a common reason motors die early.
Why should I bed new brushes in at reduced voltage?
New carbon faces are flat and the commutator is round, so initial contact is a narrow line. Running at full voltage in that condition increases arcing and pits the copper. Seating them gently first lets the faces conform, which protects the commutator and lengthens motor life.
Discount Cleaning Products is an authorized dealer with US-based product support. Our staff works with this equipment every day and can confirm fitment against your model or motor tag before you order, so the part you receive is the part your machine actually takes.
