Heat issue - blows cool out of passenger side, hot out of driver's side

[Daox]

So, I've noticed that I have a bit of an issue with my Mirage heat. It blows significantly warmer out of the driver's side vents (and defroster, and feet vents) than it does on the passenger side.

I've posted tons of info on my analysis of the issue here:
HVAC heat blows warm/hot on drivers side, cool/cold on passenger side - MirageForum.com

However, I'm also going to ask here as well because I'm still looking for help and ideas.

These are the temperature readings I got with my multimeter with a k-type thermocouple. I stuck it in the vents to measure the actual air temperature.






My first thought was a plugged heater core. The inlet and outlet of the heater core are on the driver's side and I figured there wasn't enough flow getting to the passenger side. So, I flushed the heater core out. The result was a tiny bit of corrosion, but nothing that would cause this drastic of an issue. I even soaked it in CLR overnight and got nothing further out.





So, my thoughts turn to the HVAC flapper door system. It has automatic climate control (but not dual climate control), so there are three motors / actuators that control everything. They do have position sensors on them, so they should be able to detect if they're not opening or closing fully, and I am getting no errors.

The next step was to take a tiny bore scope camera and drop it down the vents. Everything seemed normal until I found this blue tube laying very close to the heater core. I have absolutely no idea what it is or why it is there. I've browsed through the service manual a few times now and I can't figure it out. However, they don't really show much inside the heater case. It is not part of the heater core itself. The core has aluminum lines that run right out the firewall. Any ideas what this is? I'm thinking it may be blocking a flapper door, but I'm not sure as I didn't test the actuation of the doors much with the camera in the vent.









At least two other Mirage owners have the same issue I have. They haven't done as much testing as I have, but have given vent temperatures and they are similar. So, I'm looking for ideas.

I'm at the point where I'll be starting to take parts of the dash apart to get a view of whats going on.

[Stubby79]

Not under warranty?

[Daox]

Nope, the warranty is expired. I think its 5yr/60k (10yr/100k to the first owner), and I have 77k on the car.

[MetroMPG]

Given how cold it's been, I would have plumbed in an auxiliary heater core and another fan by now!

It's an odd situation. Other owners say their heaters pump out tons of heat.

[Daox]

Originally Posted by MetroMPG

It's an odd situation. Other owners say their heaters pump out tons of heat.

I'm quite glad for this. It means its not a design flaw I stumbled on, its actually a fixable problem.

[Stubby79]

Soo...the heated air has farther to go to get to the passenger side? Could it be losing it's heat to the ducting along the way? Is there more air flow coming out at the driver's side? Tried cranking the blower up on high to see if the additional air pressure/volume evens things out?

[Daox]

The higher you turn up the fan, the more noticeable it is. Airflow is even side to side. Airflow length is generally the same as well. The heater unit is right behind the radio, so its smack dab in the middle of the car. Here is a diagram of the duct system.