Replace the climate control fuse, it's bad. When there is no power on the unit, it defaults to defrost, outside air, full heat.

Needless to say, you need to re-install the PBCU.

If you KNOW you have power to it, the PBCU is bad, but this problem is usually a bad fuse.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!