charging system question
 

what should the alternator be outputting at idle and 2000 rpms?

Too many factors to consider, but generally..
On a nominally fully charged battery, right after a two second crank cycle / cold engine: 14.4 volts @750 rpm {not down to warmed idle yet}. If voltage drops at 650 rpm and before VCM goes closed loop, it's likely the battery and car want more power than alt can deliver.

After driving 20 mins, at time of shutoff. Underhood temps about 140 deg. 13.85 v @ 650 rpm. Same at 2000.
If you see more than 15 volts esp on hot day and engine warm, there's something wrong somewhere.

checked this morning and the battery showed 12.2 then I started it and it went up to 14.2 and stayed there most of the way to work, in closed loop at idle it was showing 14.1 volts. turned off the engine and meter dropped to 12.6
battery is about 7 month old, alternator is original. do these alternator have replaceable brushes and regulator like the old Delco's did.

What you see, then is normal.. didnt you say work is just a couple miles?

Each cell in the battery supports charge to 2v. Additionally there is what is called 'surface charge' of .1v each cell. Surface charge dissipates slowly over time.. such as a day, depending on amount of trickle current being used. Ex: will stay at 12.6 longer if battery terminal disconnected.
So 12.6 is nominal good reading in a RAP vehicle. In cars that shut off everything {no RAP} the voltage will drop slower as there is a ghost charge over and above surface charge that bleeds off in seconds or minutes. That's due to chemical processes still going on.

As far as rebuild parts..

Dano, bless yer heart. Dont you think it's time you venture out on yer own a little, instead of asking for fish? Pretty sure you already know how to cast a line, and what pools in our river got fish.

Just for drill, I did check Rockauto.. answer is yes and no under the vehicle listing. But your best bet is what.. call suppliers that carry parts to rebuild that stuff, right?
So pick out the ones most likely...
AZ
Advance
NAPA
O'Reilly

Now.. suppose I want to rebuild the carb on my weedwhacker.. which of those will I call to get those parts in a hurry? See the connection?

Also there's a regional franchise called KOI {think states} which may venture up into Mich.

I just remember that we used to take the old 1970's and 1980's alternators and put bearings and brush sets and new regulators in them. these newer alternator I have no idea if they had serviceable parts in them. my alt. is starting to get a little bearing noise. I thought while I am fixing everything if the alt. was rebuild-able I would just do it while I am doing everything else. I checked O'reily's for rebuild parts for alternators they got nothing, the kids at the counter get deer in the headlight looks. and as for NAPA our store here is a waste of time nobody there knows what a alternator is, let alone what it looks like, if I go in there I look the parts up myself print off a list take it in only to find out they have to order whatever is on my list, so I quit going in to NAPA.

yes I just live a few miles from work but this week and the next I have been taking a detour round to work to seek how the mileage is doing so it about 5 mile trip that way everything gets up to temp and goes to close loop.

why the concern about the alternator is the last two nights I have made a couple of small trip out to help a cousin re-wire a tractor. about 20 miles out and 20 mile back in. when I leave his place to come home. key on the volt gauge on the dash seems lower than it had been and and running down the road the gauge appears to just barely make it to 14 volts. I thought maybe the gauge might be off a little so I put a meter on it and been monitoring. voltages seemed to me a little low. also noticing the lights are not as bright as they used to be and raising the rpm don't seem to change them. this is why I was concerned

it doesn't appear that (auto zone, O'reily's or NAPA) have parts except for regulator (O'reily's)

WHY DO YOU EXPECT THEM TO HAVE THEM IN STOCK!!!!!!
you have to understand that most shops wont mess with rebuilding anymore, they work on book rate. And the implied warranty is if the tech screws it up, then the shop has to eat the parts and the labor.
Not only that but look how many more parts NAPA has to stock now than 20 years ago.. which is a lot more than they did 20 years before that. See the BIG Picture on how and why!!
I STILL get mine at NAPA. I want em to stay in business so I dont have to buy stuff from amazon.
Lemme explain... when I was a kid in the late fifties, you wanted parts for a 25 year old car you DID damn well wait for the truck.
First place there were hardly any 20 year old cars on the road. Third, parts stores were generally the size of a third tier mall specialty shop. About 400 sq feet behind the counter.

And BTW, RA does have brush kits. Just hard to find which fits the alternator application.
I've only done Fords in the last 20 years.. work fine. But I never saw a front bearing bad in one. If it's at all rutted tho you have to get a new one.. now you're looking at some money.. say 25 for bearing 20 for brush set. Reg should NOT be failing, all else equal.

Only thing I can think of would kill a regulator is the stupid trick of pulling battery terminal off with engine running AND with a semi-shorted diode. Even that's iffy.
Or maybe jumping a dead-battery car with the wrong hookup Pos to NEG