Need some guidance

[Waterloo]

One thing I learned on the 08 ProStar, only use OEM Navistar dealership expansion valves. The thermistors, I have only had to replace once. The front HVAC blower motor had a TSB for overheating. Navistar added a harness with a resistor that goes between the blower motor and the main harness. Also, try to limit the dye in the R134a, as it can really impede the cooling. Also, you must be exact on how much refrigerant goes into the system, get that wrong and bad things happen, this system is very fidgety. Then the high pressure switch, the wiring in the harness is prone to breaking near the sensor. And that HP Switch, at least on my truck, seems to fail periodically for no reason. Good thing, the system does not need to be purged to replace the sensor. Just a few things I have learned over the years. And trust me, I have thousands of dollars in this system, it has been a very punishing experience to get this HVAC system working as it does today.