How Automatic HVAC Works
Thread Starter
Lexus Champion
Joined: Aug 2012
Posts: 1,729
Likes: 132
From: Toronto, Canada
How Automatic HVAC Works
Here’s how a dual zone automatic climate control system works in your car:
I took apart the HVAC mixer from underneath the dashboard of an Infiniti G35 to see what’s inside and how it works.
Here’s the dash removed:
Here’s the entire HVAC system removed from the interior of the vehicle:
The actuators that control the flaps for the recirculate, temperature mix, and modes all have a small motor and potentiometer inside and are controlled with 3 wires on the CAN Bus.
The blower motor is PWM controlled so there’s no need for a blower motor resistor:
Here’s a look at the mixer box assembly with two actuators in black boxes on the side:
Here is the temperature mixer flap. Since this is a dual zone climate control system, the entire box is split into two after the evaporator and this flap controls the heater core by pass for each side individually:
Here’s what the inside of the evaporator core looks like. Refridgerant flows through and absorbs heat from the air cooling it and removing moisture:
The thermostatic expansion valve is the brain of the A/C system. It controls the flow of refrigerant based on the differences in the inlet and outlet temperature of the refrigerant to make sure it doesn’t freeze up or run too lean.
And that’s pretty much what’s inside the HVAC system under your car’s dashboard!
I took apart the HVAC mixer from underneath the dashboard of an Infiniti G35 to see what’s inside and how it works.
Here’s the dash removed:
Here’s the entire HVAC system removed from the interior of the vehicle:
The actuators that control the flaps for the recirculate, temperature mix, and modes all have a small motor and potentiometer inside and are controlled with 3 wires on the CAN Bus.
The blower motor is PWM controlled so there’s no need for a blower motor resistor:
Here’s a look at the mixer box assembly with two actuators in black boxes on the side:
Here is the temperature mixer flap. Since this is a dual zone climate control system, the entire box is split into two after the evaporator and this flap controls the heater core by pass for each side individually:
Here’s what the inside of the evaporator core looks like. Refridgerant flows through and absorbs heat from the air cooling it and removing moisture:
The thermostatic expansion valve is the brain of the A/C system. It controls the flow of refrigerant based on the differences in the inlet and outlet temperature of the refrigerant to make sure it doesn’t freeze up or run too lean.
And that’s pretty much what’s inside the HVAC system under your car’s dashboard!
Thread
Thread Starter
Forum
Replies
Last Post
BluesImage
LS - 1st and 2nd Gen (1990-2000)
1
May 12, 2014 10:40 AM
nickCT
GS - 2nd Gen (1998-2005)
3
Dec 28, 2007 12:21 PM
