Heat blows hot on passenger's side but cold on driver's side

[MacGuyver]

Thanks for the reply Snowbird .... I didn't explaing myself well ... I understand on the base level what the door does, what I'm wondering is how it would only affect one side of the vehicle as the blend is hot/cold ratio correct?

This has bothered me as well. While there are two 'doors' one for the heat / cold that typically gets called the blend door. There is also the gate that directs the air flow to different places in the vehicle. I'm unsure what to call that one, beyond the 'directing gate' or some such.

One thing I have heard is that because of the way the air passes over the heater core the lower part of the core gets directed to the driver side and the top is the passenger side. So as the core gets more crud in it, or the exterior gets dirty, it tends to do it from the bottom up. I don't know that this is truth, but it gives an explanation that makes sense, probably.

I'm unsure how you would clean the exterior of the core, but internally would be a super flush. Chrisfix has a video on it. I hope to do one this summer, perhaps for the whole system.

 

[VForster]

I’m having a similar issue. 2011 jk sport. I’ve just recently (as of 2 hours before posting this) had a coolant flush, dye test and Coolant refilled, new thermostat and Thermostat gasket with a new radiator cap. Water pump is about 8 months old and working fine.
My problem is that, depending on the day, My driver side vent and floor vent can be anywhere from 10 - 30 degrees cooler than my passenger side when turned to heat. In the winter time this equates to basically no heat on the driver side. The left middle vent is lukewarm and the farthest vent on the driver side is always colder than it.
I’ve checked the blend door actuator for proper function and it moves perfectly.
My heater core hoses are both hot to the touch in the engine bay before running into the firewall, and the metal pipes that run in and out of the heater core are only about 5 degrees different, ranging around 135 degrees (checked with an IR thermometer from behind the glove compartment).
There has never been a coolant smell and I can see no signs of a heater core leak.
What else could this issue possibly be? I have been told by a separate mechanics shop last winter that the heater core needed replaced, but in lieu of all the evidence I’m beginning to think that they have suggested this simply because they can’t figure out another possible issue.
ive run out of ideas and have searched countless forums.
My engine doesn’t overheat as of now, and If it is the heater core I’d rather buy a snow suit than pay to replace it since the only symptom I’m experiencing right now is poor heat on one side.
AC blows the same temp in all vents when on full Blast if that is relevant. Send help.

I have had the same issue, 2013 Wrangler Sahara. Hot heat on passenger side and basically cool air coming out on driver side, annoying as hell. Turns out (not sure what exact years were affected, mine was) but there was casting sand that apparently weren’t cleaned out of the radiator or maybe accumulated over time, but it blocks the the little passages in the radiator making it cool by the time it gets to the driver side. Ok so solution was to flush the complete system with pressure and water (I can confirm which hoses are to be disconnected if interested), I got so much sediment out of mine, sludge too. Heat works like it did when it was new. Google “casting sand in JK radiator”

 

[dap]

Thanks for the reply Snowbird .... I didn't explaing myself well ... I understand on the base level what the door does, what I'm wondering is how it would only affect one side of the vehicle as the blend is hot/cold ratio correct?

i’m having same problem . Is their a blend door on both sides of center dash or just under steering wheel area? I’ve flushed core twice raises temp on drivers side just not as hot as passengers tgen couple days later blowing cold again on drivers side

 

[Randy Brogen]

Hey Dap
As part of my installing AC where there was no AC from the factory, I pulled the entire dash out, very glad I did, though it is not for the faint hearted. I found that the Distribution Housing veins which have rubber seals had basically melted which glued them partially closed/open in some cases. After replacing that and installing AC, I can now very, very happily say I have so much air coming through that it makes your clothes move around, the heat is so hot on max that you have to adjust it down very shortly after starting and I have ICE COLD AC!!!. So in essence, the distribution housing was my jeep's problem, not the heater coil or blend door. Unfortunately, aside from removing the entire dash, the only way I could think of to examine some is maybe a borescope probe. I didn't try that since I was removing the dash anyways for the AC install.

Randy