No heat or A/C but fan blows

[aero]

I dealt with this all summer, having no a/c, but now that it's nearly winter, having no heat isn't just a comfort issue, as I can't defrost my windows the initial drive to work gets a little hairy sometimes.

When I turn the knob it does blow but it's not hot...what are the probable issues and is there any way to tell for sure? My initial reaction is the heater core obviously, but perhaps the a/c not working is a related issue?

Any input would be appreciated...

It's an 87 eta if that matters at all.

[porsche gt1]

if you have only your second switch for positions of the fan to the right and no hot air comes out. Then I would say it is your heater core.