The loaded voltage is the real issue here, not the ripple. 12.7 loaded is akin to not charging under load. Realistically it is, but just barely, loaded non charging I’d expect it to be lower, like 11.9-12.3. If the alternator is accessible, I’d try cleaning and tightening both connections (one on either end) of the big wire coming off it, and then seeing what the voltage is with the headlights and blower on full.
The loaded voltage is the real issue here, not the ripple. 12.7 loaded is akin to not charging under load. Realistically it is, but just barely, loaded non charging I’d expect it to be lower, like 11.9-12.3. If the alternator is accessible, I’d try cleaning and tightening both connections (one on either end) of the big wire coming off it, and then seeing what the voltage is with the headlights and blower on full.