2004 4runner sport v6 4.0L.
I get heat only on the driver's side of the cabin - the passenger side blows cold. A/C works on both sides.

I've tried flushing the heck out of the heater core.. Any other "low hanging fruit" explanations?

Much obliged,
Kris

I had the exact same problem. Chances are you're low on freon. I know, I know, It doesn't make sense why it would blow cold on one side and not the other just being low on freon, but give it a shot. Pick up one of the recharging cans at your local autoparts store for $30 and give it a try.

I think that what the OP is trying to say is that heat only blows on one side WHEN HE IS TRYING TO RUN THE HEATER, NOT when he is running the A/C. In fact, he stated that the A/C works just fine on both sides. This is not a low freon issue. Sorry for the clarification.

Yeah I know I'm asking in the wrong season

@ke123 ,

No, don't be ridiculous. It's perfectly normal, assuming you are off-roading in Antarctica.

Could one of the hvac blend doors behind the dash be stuck?

See if this helps
http://www.toyota-4runner.org/showthread.php?t=132774

Okay so I've 75% solved this problem.. I flushed the heater core again, using hot water and a drill pump, in both directions (put about 5 gallons through). I blew it out with 30 psi compressed air between direction changes... Filled it with CLR and let it sit about 2h. Then i set up a recirculation system to flush 50% CLR in both directions.. Then i flushed with water again, both directions, then filled with distilled and blew that out with compressed air.. Filled with coolant, and now I'm sitting here bleeding the system using a spill free funnel.

Passenger side heat is at about 75% on the right-most vent. The center-right and rear vents are perfect.

The wife is pleased

This'll get us through winter, maybe next summer I'll repeat it again w/ a longer soak..

I know it’s an older thread but I can’t post a new one yet. Too new on the block!

Great heat on the driver’s side and to the rear but nothing but exterior air coming in on the passenger side. Also much lower air flow on passenger side from all 3 vents - defrost, dash and floor vents.

A/C works perfectly. Had a new rad installed about 10 days ago on the road so can’t go back. Said they did a system flush. New thermostat too.

Don’t have anything but the Haynes manual to refer to (I know!) and trying to figure out if somehow I ended up with a partially blocked heater core (checked temps on the heater hoses - 195F in and about 145-150F coming out with heater on Hi and fan on full). Still trying to figure out how a blocked heater core can put out full heat (and air movement!) on one side of the truck, but no heat and low flow on the other per other posts I have read.

Or if there’s a baffle on the passenger side that is only actuated when the heat is on and the a/c is a separate baffle and set-up, since I get full cold and air flow with a/c.

So - no heat and low air flow from all 3 vents on passenger side. Driver’s side is excellent. And a/c is perfect.

Suggestions? 2006 V6 SR5

Also…. I’m happy to do a back flush on the heater core if that’s the likely culprit, but would rather not muck about with the very well attached hoses if I don’t have to!

Still doesn’t make any sense how a baby radiator (heater core) can be partly plugged and still put out full heat on one side of the truck but nothing on the other, unless there’s something going on behind the dash around the blower and baffles that I don’t know.

I am experiencing the same thing. Decent heat out of the far left vent and then less and less as you move to the passenger side.

Ordered a heater core and evap core since the evap core is leaking anyway.