A question for the experienced in the Climate Control world.

I have a W123 300D with the early servo-type CC system. Ever since I've owned it, it has only blown in the default full-heat mode. I know my compressor is locked up, so I'm not expecting AC, but I'd like to at least mix the scalding hot air with outside air for more comfortable heating.

The different fan settings (auto-lo, auto-hi, bi-level, def) all work with approriate changes in fan speed, though there is a 5-7 second delay on shut-off and start-up of any mode, save def.

Any ideas? Vaccumm leak I'm guessing, but I don't know where to start. I'm sure I'm not the only one who has experienced this

Thanks much in advance,
- Ryan

__________________
'95 E420 - 'Shadowfax' 138kmi.
'92 Volvo 740Turbo Bard 193kmi
'74 240D - 'Ol' Green' 4spd Manual 104kmi. (sold )
'77 300D - 'Red' 223kmi (sold)
'75 240D - 'Bianca the Blue Bomber' (sold)