Originally Posted by ehsnils
Please read the thread I linked, sludge buildup in the heater core is manifesting itself as bad heat on the passenger side, which means that a flush of the core is one of the first things to try - before removing the whole package under the dashboard, which sucks big time.
I understand what you mean, and I read that post. I also read what others had said and that they had success with that, but what I'm trying to explain, from a mechanics point of view, is the heater core is one unit. If it got "clogged" why would you have poor heat on the passenger side and not the drivers side. The heater core is on the passenger side of the car so wouldn't you think the driver side would have poor performance and not the passenger side, considering how the amount of ducting the heat now has to travel to get to the driver side vents. Something just doesn't make sense. What makes sense to me tho is what I posted from Subaru of America. Look at how many people posted about having the SAME issue. That's why TSBs are released. Does their response suck? Sure it does, who wants to hear that what they're experiencing is within normal parameters.
'05MY - 06MY LEGACY/OUTBACK CENTER DASH VENT TEMPERATURE
If you get a customer concern that the air temperature coming out the center dash vent is different on the driver's side than on the passenger's side, you can inform the customer that up to an 18°F difference is considered normal, and that no repairs should be attempted.
Anyone can do what they please. If they wanna flush the heater core cause they think it'll fix it, then fine. I'm just lending my .02 with information directly from Subaru.