For possible future reference

[Dads72]

Sent a post called "where did my heat go" and received zero replies.
Now I know why.
Here's the deal.
Shut the heat off under the hood using the valve on the passenger's side on the firewall. Wanted to get the heat back yesterday, so I moved the valve the other way.
No heat.
Checked today and found the fan/alternator belt was way loose.
The bolt that holds the alternator bracket to the block was broken. Everything had gradually shifted.
The water pump wasn't turning, hence - no heat.
Everything is fine now, but I don't want to remove a broken bolt in the head again. PITA.
Hope this helps someone down the road.