HVAC Blower motor issues. 2008 Prostar

[Waterloo]

Alright guys! The HVAC front blower motor only runs when it wants, usually at low speed. I have replaced all fuses, breakers, the spiked resistor/module, everything related except for the blower motor itself... Any of you guys have this problem before? Sitting, the blower will not run. I start driving, the blower runs, but only when it wants. It will run on high for a minute or two and then shut off... Filter is fine. Took it to dealer, no codes. I was just under the dash, wiring looks good, as do connectors. Going to put old working blower motor in tomorrow, when it quits raining here and try that. Any help appreciated.