DIYbanter - View Single Post - Why would ONE carbon brush burn on an DC motor

Ignoramus15926

On 2015-10-16, wrote:
On Thu, 15 Oct 2015 20:53:37 -0500, Ignoramus15926
wrote:

I got a nice Matrix T3X treadmill at a company cleanout.

Seems to be USA made, heavy, for up to 400 lb max runner weight,
with a US made Johnson 3HP motor etc.

Except that it sode not work and gives "Error 1". Some googling
revealed possible reason as "burnt brushes", so I took the brushes.

One of them was indeed burnt, as follows: evidence of heat damage, the
helical spring was no longer pushing it apart, and two out of three
strands of copper wire were burned.

The other brush was in a fine condition.

What I do not understand is how could only one brush burn out?

Any idea?

i
On those motors it is not uncommon for a brush to stick a little,
which causes it to heat up, and the brush spring looses tension. Then
the brush has even less pressure on the commutator, so it starts to
arc, and pretty soon the brush has burned off - and the spring is
totally toasted. The other brush can be totally OK.

OK, this is great. I bought replacements from the mfgr, cannot wait
for them to arrive.