So I'm in the need for some troubleshooting advice.

Today was the first warmish day in a long time so I lowered the heater to just use the vent at low temp - at this point I did not turn on the AC. All I got was more hot air coming from the vents. I tried every option with the climate control settings and still only hot air. Keep in mind it wasn't even 60 degrees out so the vent temp on low should have been fairly cool.
Finally I tried the AC and still only hot air.

I'd appreciate any thoughts or advice on where to start my search for the cause.

It's a 2003 R53. The temp gauge never went over 200 degrees even when I shut off the vent/heater all together.

 

Auto or manual climate control?
I have Auto...
To just use it as a VENT, I just set temp to LO, then turn off the A/C, and set the fan where I want it...all the way off the lights will go off..and air will just flow--AT THE LAST SETTING BEFORE YOU TURNED OFF THE FAN....BOTH temp and vent selection.
This trick CAN be used to your advantage....I frequently set just a bit of heat...then turn off the fan....

A few thoughts....the car seems to be running warm....
Have you heard the fan radiator fan running? Both low and HI...if you just hear HI cycling on and off (loudly) then you have a radiator fan issue...the low speed should be nearly silent...and is what cools the car 90% of the time...

As for the heating issue (is you are using it right and gave it a few seconds to adjust)
you MIGHT have a stuck/failed blend door....or maybe an controller (push/pull rod) got knocked off the blend door...
the arrangement is different on AUTO and manual systems...

 

thanks Zippy!

It is auto and I know I'm using it correctly. I'm hoping you're right about the stuck blend door - where might that be located?

As for running hot - I was thinking that as well. I had done a flush, changed the Tstat, water pump, and fan assembly late summer last year when I did the SC oil service. But now that I think of it I dont think I remember noticing the fan running at low speed. I guess I'll have to trouble shoot that as well. What temp would that kick on at?

 

so today I get in the car and instead of heat, I have nothing but cold outside air or AC. Seems like the blend door is the issue. Anyone know where exactly that might be located? I checked bentley and found nothing.
Any advice would be greatly appreciated.