1970 blower motor

When I turn the igntion on the heater/ac blower motor works, when I start the car it quits.

There may be a connection problem in the power wire to the ignition switch. Check the voltage to the switch and see if it is over 12 volts while the engine is running. If that is ok then there may be something wrong with the switch contacts.

These cars had “Astro Ventilation” and the blower ran anytime the key was on. There was no “off” position for the blower. I suspect it is running all the time…This feature was supposed to pressurize the cabin and keep any stray exhaust gas and dust out of the car…