I have a 2007 S197. I was having issues with the AC/heater controls unit. The zone selector switch was acting sporadically. I replaced the unit (with a used one on eBay) and that fixed that issue. But then I started having issues with the blower speed switch. There's a clear difference between 1, 2, and 3. However the blower doesn't speed up for 4. I've replaced the blower motor switch with a brand new one, replaced the resistor and the blower motor and made sure none of the connectors were...

Blower motor speed issues 2007 mustang gt