Slow Crank, Diagnostic Advice? Options

[SteveL]

I hit the key, and she cranks the starter a bit slow for a couple of turns then dies out. Acts exactly like a low battery.
Battery is new (1 month old). The car has not been driven since the new battery was put in, but it was started several times, and allowed to run a while. At first it cranked over just fine as you would expect with a brand new battery.
Last week, the slow crank and die started. Charged battery, same thing. Brought battery to Interstate, they tested it and said it was fine. Cleaned all major connections - battery post connections, trans ground strap, battery ground to body, battery cable connection at starter. No improvement.
I do have a starter relay installed, it has been there for many years.
Help Please! I stumped.

[Tom]

Sounds like the starter may be going bad. The brushes in the starter are carbon and the commutator eats the brushes over the years. The resulting dust acts like a resistor and less voltage/current gets to the motor part of the starter. Sometimes disassembling and blowing out with air will help. If it is too oily/greasy, them more is needed to clean the dust out.
Tom