And it's on club reg! Also needing to find out where the alternator external reg is - not charging

And it's on club reg! To say im happy is an understatement, so keen for the summer cruises.

Also just needing to find out where the alternator external reg is as it's not charging and wanting to try that first!

Kieran - congratulations on the club reg..

The external alternator regulator on the W108 280SE 1969 is mounted on the LH inner guard, approximately 200mm forward of the firewall, directly above the brake master cylinder.. its a small black Bosch box approximately 80mm x 60mm x 50mm with 3 spade terminals (D+, DF, B+) plus the chassis earth via the mounting bracket. Mercedes-Benz part number 000 154 12 06, Bosch part number 0 192 052 005.

Before replacing - check the obvious first:

1. Drive belt tension - should deflect approximately 12mm at midpoint between alternator and crank pulley. Loose belt = no charge.
2. Earth strap between engine block and chassis - corrodes after 50+ years. Clean both ends back to bare metal.
3. B+ output cable at alternator - the lug crimp fails internally. Test voltage AT the alternator output (should be 13.8-14.2V with engine running). If you see correct voltage at the alternator but no charge at the battery, the cable is failed.
4. Regulator spade connections - one of the three is often loose or corroded.

If all four check OK and you still have no charge, replace the regulator. New Bosch unit $145 from Mercedes-Benz Australia, $95 from Pelican Parts USA. Five-minute swap once you have the part.