1997 Dodge Dakota Blower motor quits

Hi:
If it doesn't start intil you hit a bump, you have a loose connection or a broken wire. The first thing I would look at is the blower motor resistor. I believe it's located on the passanger side firewall of the engine compartment. Several wires in a plug will be connected to ther resister. Often times, from heat the plug gets so hot it starts to melt causing a poor connection.

Let me know if this helps.

Joe