Ok everybody, I am new here but I have a weird issue and I'm not sure where to begin looking. 2001 Ford F150 Harley Davidson. Yesterday I was driving with the heater on, truck felt a little boggy (under powered slightly). Came to a stop light and the rpms started fluctuating like it wanted to stall. Start driving again and it seemed ok. Then I started getting a loud whining screeching noise that seemed like it was coming from the blower motor area under the dash. Lasted for about 30 seconds and went away. I turned off the heater and some power came back into the truck. Stop at a stop light and it ran fine. Turned heater on while idling and it immediately died. Started up truck and it wanted to die while idling until i turn the heater off and then it seemed ok. I do notice a whining screeching sound coming from the truck when I am outside of it while it runs. Sounds like it might be coming from the pulleys but I can't tell. Plus that makes no sense, when I turn the heater on the sound (which is intermittent) clearly seems like it's coming from under the dash. Anyway, I don't understand the connection between turning my heater on and the motor dying. No CEL and the voltmeter doesn't change at all. Temp is good. Oil pressure is good. Any ideas where to begin looking?
Vacuum leak? Electrical?
I am currently on crutches so I can't do a lot of climbing and crawling around. So any direction would help cut down the time I'm working on it.

Sorry for the book.