charging woes

i've got a 66[?] suburban 12 w/ the dual function starter/gen system. the batt is good[been load tested etc] with each start the batt gets weaker. the starter function is great. i haven't been able to put a meter on it yet[lent out] but seems if it motors it should gen. i,m thinking regulator. any thoughts? will any old style 12v reg work?

Try the easy stuff first with the regulator. Make sure the ground is good on all the contacts. The regulators are rubber mounted and have a separate ground wire that will get corroded or break. Most can be taken apart and inspected/cleaned.

thanks......s

A good easy check is the brushes inside the starter generator. If these are bad it will start but not charge.
I am blessed to have a u-pull it yard nearby that has a lawnmower row. These delco starter/generators were used on a lot of older garden tractors and can be found in good shape after the unit is scrapped for engine or transaxle woes.