Today on my way home from work the volt gauge on the dash was reading low and I got a check engine light. The codes stored were 12 41 and 55. I checked out the sticky for codes and see that 41 is generator field not switching. And code 12 is battery disconnecte and I did find a loose ground on the battery. Since the summer the volt gauge on dash was reading low at idle but would sweep back up at speed. With the fluke volt meter I was getting 12.20 at idle ANd up to 13.80 at say 2000rpm. With lights on I could not get anything above 12.00. Kind of thinking the altenator is just not handling any load. It's the original 275000 mile unit.

 

Funny thing is, it is likely that a set of brushes is all it will truly need to be a working unit once more.

You might also double check that the crank sensor is not failing, but it likely is not.
If you have a factory tach and it is working correctly, then the crank sensor is likely good.

Mark.

 

I figured the tach was a good indicator of the crank sensor working. I'm hooked into the factory tach location and would imagine that's how it gets it's signal. Are the brushes servicable and avialable?

 

The brushes are serviceable and IIRC, you don't even have to take the alternator apart, they are removable externally.
As far as being available, I'd check with your local area generator/starter rebuilder and see if they have any.

Most of those places can at least get that kind of stuff.

Mark.