If the blower is running at the correct speed (fast on high, slow on low), the monovalve is likely failed and staying open or the PBCU is fried (as Larry said, could be the aux pump drawing too much current).

If you don't have a blower at all, just blistering hot air, the fuse in the fuse box under the hood is bad and you have no climate control all. Replace all the fuses, they are getting corroded by now.

If a new fuse fixes the heat but not the blower, check the strip fuse for the blower, it's in a small snap top black box just in front of the fuse box, just a metal strip held down by two screws. Chances are, it will be cracked so that when you touch it, it will bend apart. Costs about $0.50.

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!