[Fred Taylor]

It is unlikely your dial, which BTW you can cean by more than one way.
It is likely the bulb or the way the light goes.
Don't know if it has lens, but try to align or see if the bulb is wrong, or....

The plastic dial has turned darker from age and , I put a brighter bulb in and doesn't do much, I put a bright flashlight against dial and doesn't do much ether. , thinking the plastic faded darker all the way  thru the thickness of the plastic, not much I can do?