Sharing a success story for group knowledge. 1974 1.8L. Getting car out from winter slumber, charged battery, changed oil, etc. Sluggish to turn over and battery/system voltage inconsistent. Load tested battery with fine result (2-year old Optima Red).
Consulted Haynes and George Hussey’s 914 Guide. Checked starter connections (all ok). Replaced voltage regulator with known good used one (saving my NOS in box for whatever reason) and removed, cleaned, reinstalled body/trans ground strap.
Runs like a champ and all volts on the console meter where they’re supposed to be.

Next up - the thermostat wire is down to one strand. Next week......

Good to hear.

So what was the problem? You mentioned the VR and trans strap. Likely only one of them was causing the issue.

What was the final solution? So many times it's a bad ground(s).

The voltage regulator. The ground strap was in pretty good shape; replaced the strap about 20 years ago and cleaned it about 10 years ago. Just did it again anyway to be extra super sure.

Unrelated to 914's but swapped out an alternator (internal regulator) on our 1994 Jeep. It's had a slow drain ever since. I'm 99% certain the VR in the new alternator or a diode is bad.

Not easy drains to find, good job!