With engine OFF: Check for a slipping alternator belt.

Try turning the alternator pulley with your fingers.
Push on the cooling fan blades behind the pulley.
If it slips,(i.e, doesn't move the crank/fan/etc. with it),
tighten the adjuster just enough, not too much.

Replace the belt if it is old. Use a Volvo OEM belt if you can.
They seem to be better quality. Some old belts tend to slip (& squeal) even if you over-tighten the adjuster. New alternator belts grip better & slip less.

14 volts, not amps.

Check wiring. Connections to alternator, starter and battery. Grounds. Make sure everything is clean, dry and tight, with shiny metal.

You have poor charging; it will be the alternator brushes, which any auto electric shop will replace and bench test for about $20.

An hour sounds about right for a no charge situation. It's not expensive to deal with if you are smart about it, just don't get talked into a "new" alternator which is a complete rip-off.

--
Stef (rewired harness, rebuilt Bosch 55 ampere alternator Interstate MTP-65 battery, speedo/odo converted to miles, scotia blue 81 245 B21A SU M46 3.91)