HVAC Dual Climate Zone Control Engineering

[webduelist]

Hi All,

I am am a engineer by trade so I like to understand the systems that I am looking at and using at a extremely detailed level. That being said I am looking to see if anyone is willing to share any CAD, illustrations, photos of the dual zone HVAC system. I understand the single zone well enough, ie pull air in with a blower motor and shove air through a hot or cold radiator. What I am having trouble figuring out is how it regulates two zones, as it seems like there is only one charge box pushing air through.

It seems to me the only difference between a DZ and SZ is a blend door actuator on the drivers side and 2 temp probes?

Side note: Seems like this would be a very tricky modification if someone wanted to try and make it DZ, as that one blend door is buried in the core of the unit. Unless its already two blend doors just moving together it would require a actuator and the blend doors to be replaced on both sides. But also very easy if your already say doing a heater core and have taken the air box out, something to keep in mind

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[Gvsukids]

Hi All,

I am am a engineer by trade so I like to understand the systems that I am looking at and using at a extremely detailed level. That being said I am looking to see if anyone is willing to share any CAD, illustrations, photos of the dual zone HVAC system. I understand the single zone well enough, ie pull air in with a blower motor and shove air through a hot or cold radiator. What I am having trouble figuring out is how it regulates two zones, as it seems like there is only one charge box pushing air through.

It seems to me the only difference between a DZ and SZ is a blend door actuator on the drivers side and 2 temp probes?

Side note: Seems like this would be a very tricky modification if someone wanted to try and make it DZ, as that one blend door is buried in the core of the unit. Unless its already two blend doors just moving together it would require a actuator and the blend doors to be replaced on both sides. But also very easy if your already say doing a heater core and have taken the air box out, something to keep in mind

Did you ask your dealer? Maybe @AllMoparParts.com knows.

 

[webduelist]

Did you ask your dealer? Maybe @AllMoparParts.com knows.

If there is one thing I have learned is that FCA does not like to admit anything and keep even the dealers in the dark on a lot of stuff.

For example one of the things I have learned reverse engineering the system is that the Distribution box is the same between Single Zone and Dual Zone, it has always been assumed that there were baffles or blend doors missing, nope exactly the same, what I don't fully understand yet is how its moving the driver and passenger blend doors at the same time just using the passenger side actuator. The Blend doors look identical between SZ and DZ distribution units so my speculation that it was just one big door on SZ units isn't correct... Maybe it only uses the Passenger Side Blend door and is dumping into a non separated duct... not fully sure.

 

[swtrailboss]

Sorry not an engineer. As a mechanic I can tell you the air handler is the same size from single to dual zone but the air handler in the dual zone has two temp control doors that distributes to two zones ( center left or center right) instead of all vents being the same. Instead of just the one temp control door it’ll distribute hot/cold air to left or right sides.

 

[Wildtoad]

This might help

 

[webduelist]

Sorry not an engineer. As a mechanic I can tell you the air handler is the same size from single to dual zone but the air handler in the dual zone has two temp control doors that distributes to two zones ( center left or center right) instead of all vents being the same. Instead of just the one temp control door it’ll distribute hot/cold air to left or right sides.

It seems to me on this one that FCA used two blend doors to regulate the output, and the right side actuator exists, I just don’t understand how the left side is moving. But I could also be completely wrong, I don’t have a unit to take apart.

as far as I can tell from the outside the only thing obviously different from outside examination is the drivers side missing an actuator, I included a picture highlighting the drivers side blend door actuator mount on a SZ air box, it looks like there is something there, is it a blend door being unused? a plug,? I have no idea.

 

[webduelist]

I try not to double post but in the interest of reporting findings.


After investigation into the blend doors on a SZ airbox it was discovered that all blend doors and baffles for a DZ HVAC Airbox where present and functional in a SZ HVAC Airbox. Further More these blend doors act identical in the DZ HVAC Air Box as in a SZ HVAC Air Box. The only real difference between a SZ and DZ HVAC Airbox occurs with the Drivers Side Blend Door.

The Blend Door that regulates hot and cold on the Drivers Side is functionally identical in a SZ Air box as a DZ Air box, however as noted in the photos the Drivers Side Blend Door in a SZ lacks the external connection for Actuator Gearing, and features a internal plastic gear that links this blend door the Passenger Side Air Box.

This leads to the question of upgrade ability, at this time the difficulty of removing an Air Box Baffle would be more intense than simply replacing the the entire HVAC Airbox.

Please note that this is just engineering and not a guide to convert a HVAC Air Box from SZ and DZ, any attempt to do so is at your own risk and I will not be held responsible.

With this knowledge there does appear there may be a path available to covert from SZ to DZ fairly easily however there is much engineering work to be done on this matter to make it safe and no one should attempt to make any modification on their jeep.

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