I have a 79 300td and the only two buttons that work on the climate control unit is the defroster button and the off button. It turns on the fan full blast and I get heat. Nothing else on the push button unit works.

Now lately sometimes when I push the defroster button, the fan wont go on, or when the fan is on I cant turn it off!

I notice when I put my finger in the defroster vent when the fan isnt running I'm feeling heat in there, so I'm wondering two things: is it just the push button unit and most importantly:

For now can I just rig a switch right at the fan, Im saying just run a + and - wire with a on/off switch right to the fan, to operate it manually for now. Its winter, and I need the heat! Any suggestions, advice or anyone out there that did this?

Thanks!
Mike