I will make this a sticky once people know it is here.
I had this problem 10- 12 years ago and again this past week.
CEL Illuminated With A Code 41 (Alternator Field Circuit Not Switching Properly)
Cause: (SEE PICTURE #1)
Worn Brushes Not Making Proper Contact With The Commutator
A New Brush Holder Can Be Purchased for Under $10.00 on eBay.
I Stock One.
1)1/4" Drive Ratchet
2)7 mm, 8 mm, 10 mm, 12 mm - 1/4" Drive Deep Sockets
3)#2 Stubby Phillips Screwdriver
4)Compressed Air (Can For Computers Will Work Fine)
5)CRC QD Electrical Contact Cleaner or 91% Rubbing Alcohol
1/2 - 3/4 Hour W/Alternator On Car
1)Disconnect and Isolate the - Battery Terminal.
Remove the wiring from the rear of the alternator.
After all of the wiring is removed then remove the remaining 12 mm nut from inside the plastic battery cable guide on the rear of the alternator and remove the guide.
Remove the three nuts holding the tin cover to the rear of the alternator and remove tin cover.
Remove the three Phillips screws holding the brush holder to the alternator and remove the brush holder.
5)Use the compressed air to blow out all of the dust in the alternator from the old, worn brushes.
6)Use the electrical contact cleaner or alcohol to clean the commutator and electrical components in the rear of the alternator.
7)When installing the new brush holder use the toothpick to depress the brushes in the holder while sliding it over the commutator.
8)Re-install all of the other components in the reverse order they were removed.