Check the OVP or MAS relay.

sudden bright headlights is a bad voltage regulator in the alternator, about $30 and two screws to change it. A loose positive battery cable can do this, too, though, so check that as well.

If the OVP fuse is blown or you are getting overvoltage events, it may be open all the time, so the climate control won't work. It's there to prevent just such damage (fried electronics) from voltage surges when the regulator goes bad, etc.

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!