Problems with 90mm 12v generator

[Rocket Ron]

Having fitted a generator to my car which had been in storage in the bottom of my wardrobe for a few years I am having a few problems.

It still appears to be good and spins when it's polarised but it gives out a voltage reading that's jumps from anywhere from zero to 14v when tested, brushes seem good and belt is tight

Any suggestion would be welcomed

Thanks in advance 

[benssp]

Check that the slots on the commutator aren't bridged with carbon from the brushes 

[Rocket Ron]

Will take a look bud

Cheers Ron