65 Dart Heater AC Fan Problem

In 69 the fan is wired differently for heat and a/c. I think one of the blower resistors is in the circuit all the time on heat to make the fan run slower. On a/c there is no resistor in the circuit on high so the fan runs faster on a/c to move the cold air. Replace the blower resistor & see if that helps.
Thanks Mike. I did ohm that resistor, and all looked well as I was working on the problem. I did resolve the problem as the new switch was wired differently on the tabs....back side. As well, I had a problem with the vacuum actuators. With that said, the AC/heat door would not open and close....this caused the air to continually blow through the AC. Thanks for the tip. sgrip65