Some questions in my build thread about more details on the HVAC controls spurred me to do a tech thread of sorts.
The whole HVAC is comprised of three primary parts. The intake and blower motor are on the far right (for a LHD vehicle) and includes the diverter for fresh/recirculated air supply. It also includes your blower motor and blower motor resistor. It fastens to the firewall and mates up to the fresh air intake that opens into the area behind the hood. Here's a shot of mine after clean-up and new foam/seals prior to install.
There's an AC housing which sits in the middle of the whole setup. It sits to the left of the blower motor and fastens to the firewall as well as to the blower motor housing AND "mixer" housing. For non-AC units this is essentially just a pass through duct. For AC trucks this has your evaporator, pressure switch, and a drain. The evaporator has two lines that pass through the firewall to be plumbed to the balance of the AC equipment in the engine bay. Here's an end-view of mine after clean-up and new foam/seals/pressure switch.
Finally, there's a heater and "mixer" unit that sits in the center of your dash. It sits to the left of the AC housing and fastens to the firewall. This houses a heater coil (on trucks with heat) as well as multiple foam-covered flaps that divert air between different diffusers (defrost, floor, front vents, side vents). This unit has two lines that pass through the firewall to be plumbed to the appropriate coolant lines for heat. Here's the heater-featured unit I rebuilt for my truck recently.
The whole HVAC is comprised of three primary parts. The intake and blower motor are on the far right (for a LHD vehicle) and includes the diverter for fresh/recirculated air supply. It also includes your blower motor and blower motor resistor. It fastens to the firewall and mates up to the fresh air intake that opens into the area behind the hood. Here's a shot of mine after clean-up and new foam/seals prior to install.
There's an AC housing which sits in the middle of the whole setup. It sits to the left of the blower motor and fastens to the firewall as well as to the blower motor housing AND "mixer" housing. For non-AC units this is essentially just a pass through duct. For AC trucks this has your evaporator, pressure switch, and a drain. The evaporator has two lines that pass through the firewall to be plumbed to the balance of the AC equipment in the engine bay. Here's an end-view of mine after clean-up and new foam/seals/pressure switch.
Finally, there's a heater and "mixer" unit that sits in the center of your dash. It sits to the left of the AC housing and fastens to the firewall. This houses a heater coil (on trucks with heat) as well as multiple foam-covered flaps that divert air between different diffusers (defrost, floor, front vents, side vents). This unit has two lines that pass through the firewall to be plumbed to the appropriate coolant lines for heat. Here's the heater-featured unit I rebuilt for my truck recently.