Other than the brushes wearing down, regulators do not fail often. However, a spare is always nice to have. I suggest buying and installing a replacement regulator. If that solves the problem, well and good. If it does not solve the problem, leave the new regulator in place and put the old one away in the trunk as a spare.

An old, weak battery can also be the cause of the problem you are seeing. If you don't want to buy a new battery (on top of your new regulator), maybe you can borrow a good one to see if that helps.

Other things to check are the battery cables and their clamps on the battery terminals, the wires at the alternator, and the big ground wire (flexible strap) between the engine block and the car's chassis (usually underneath and not too far from the starter motor).

Jeremy

__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970