Brain teaser - help me fix my sander please

[Saleen836]

I have a 110v drywall sanding machine that I use for work that I run off my generator, while using it a coule weeks ago it stopped working so I replaced the carbon brushes and still wouldn't work, got home and checked the plug wiring and everything ok so plugged it into my 240-110v transformer and it works (although running slower than before). Went to use it at work on my generator a few days later and nothing, it wouldn't work again!
Got home and plugged it into the transformer and it works
I plugged the transformer into my generator (it's a 110/240 genny) plugged the sanding machine into the transformer and it works!

Have replaced the on/off switch no difference and even bypassed it still n difference, tested every wire I could and everything checks out, even replaced the adjustable speed setting switch and still no difference.

Anyone have any idea before I throw it in the bin?

[KnackeredOldBanger]

Issue on the 110v supply side of the generator?

[Saleen836]

KnackeredOldBanger said:

Issue on the 110v supply side of the generator?

Tested the generator and it is showing 115v at the sanding machine

[IJWS15]

Saleen836 said:

Tested the generator and it is showing 115v at the sanding machine

Is that loaded or no-load?

[Saleen836]

IJWS15 said:

Saleen836 said:

Tested the generator and it is showing 115v at the sanding machine

Is that loaded or no-load?

The generator connected to drywall vacuum and a mixer both work perfectly,
115v was showing at sanding machine motor not directly at the lead that came off the generator

[OutInTheShed]

I'm wondering if the transformer is +/-55 relative to earth while other things are 0, 110?

So an earth fault might make a difference?

[KnackeredOldBanger]

Saleen836 said:

Tested the generator and it is showing 115v at the sanding machine

I'm far from electrically literate but with you saying it ran at half speed could it be that the 110 output fault is causing the wrong frequency or amps so the tool behaves differently.

[Saleen836]

OutInTheShed said:

I'm wondering if the transformer is +/-55 relative to earth while other things are 0, 110?

So an earth fault might make a difference?

I have no idea it has me stumped

KnackeredOldBanger said:

Saleen836 said:

Tested the generator and it is showing 115v at the sanding machine

I'm far from electrically literate but with you saying it ran at half speed could it be that the 110 output fault is causing the wrong frequency or amps so the tool behaves differently.

I do have an old motor so at some point will put that in and see what happens, guess doing thos will show if it is the motor at fault or something else