My first post was wrong. I did find the fuse for the turn signal, climate control and horn broken. Replaced the fuse and, turned on the heat and smoke came from the dash where the temp sensor fan and vacuum switchover valve is located. There has always been a tapping or popping from that area when the heat has been on therefore I suspect the switchover valve. I attempted to repeat the failure for a third time while I watched to see where the smoke came from. Had to remove the glove box to visualize the components. No failure this time. I did push and pull the electric plugs to make sure there was good contact. Maybe that cured it.
'00 Mazda MPV Family's car
'83 300D 235,000
'84 109E 175,000
'74 280C 125,000 in garage; needs rehab or sell for parts???