Rear heater problem - cold air only

[Vlad]

Hello there folks! I'm the new one here.
My apologies, I've searched for my problem solution, but came across the two old threads with the same problem (one in Armada, one in QX forum), which end up with nothing, no solution. Appreciate your ideas as to what it can be - 2004 QX56, rear heater blows only cold air. Controls work well both front and rear, rear heater responds, changes modes floor to overhead, but whatever I did with controls (back and front) it keeps blowing cold air only.
PS: front heater is hot.
PPS: I know the rear heater in overhead mode gives only cold air, so all my attention is nailed to the floor vent in the floor mode.

thanks

[scr38]

Check to see that radiator is completely filled. A low level could cause an air pocket in the lines to the rear, resulting in no flow. Remove the radiator cap when the engine is completely COLD and see that the level is all the way to the top. Then check the overflow bottle to see that the level is OK.

[Vlad]

Thanks for your reply. Just checked both. Radiator coolant is ok, can see the level under the cap. The bottle level is on minimum, so its not empty. Can a min level in the bottle cause rear heater cold air?

[scr38]

When the rear is set to heat does any air blow from the floor vents?

[Vlad]

Yes, exactly, it blows cold air any mode and changes modes from top to the floor, where on floor it should be hot

[Vlad]

Well, a quick update: I went to the local shop just to talk to servicemen, hell, I was surprised one man there said this is a known problem. He was busy and from what he said I understood that to remove this problem he should open up the front dash and do the heater servicing and cleaning, in particular some flaps in the front that got stuck in closed position and dont let the coolant to the rear heater... Not sure how right he is, but he sounds like he has knowledge and confidence... he said he dealt with it a few times before, he warned this is going to be costly, around 1K, so I dont feel like I want to do it.... at least not now, may be some time later. Grateful if anyone here has any opinions to share.

[ntrddragn]

not sure if you saw this but it could be your rear actuator door not opening. here is the how to thread.

http://www.clubarmada.com/forums/showthread.php?t=19985

here is the titantalk thread. the link on the thread above is dead.

http://www.titantalk.com/forums/tita...ml#post1990867

[Vlad]

thanks for this advice too. I actually do have this problem with defrost/floor actuator as well and I do have the new actuator just need to replace it, thanx for the link to clear instructions, I might do that now by myself )) But I wouldnt think this can have any relation to my rear heater blowing cold air? I mean yes, the front heater produces clicking, but it blows good amount of hot air, so I dont bother about that clicking much (you can hear it only if you spend extra time inside after you have stopped the engine), I just keep the front heater almost intact on feet mode where it blows equally to the frontshield and the floor (actually a little less to the floor, which is not a big problem). I'll fix it anyway of course. But I dont think that bad actuator can impact the rear heater, am I right or wrong?

[scr38]

I don't think you have a problem with the rear damper because you have air blowing from the floor ducts when the rear unit is on heat. It sounds like you aren't getting coolant circulation through the rear heater core.

[Vlad]

Agree that clicking in the front has no relation to cold rear air. And the mechanic said that coolant supply to the rear is blocked by the front heater valves, which need good cleaning... well, I'll see... I will replace the actuator in the front, but I havent made up my mind about fixing the rear heater coolant circulation, sounds like its going to be time and cost consuming whereas I dont suffer much from the rear heater not being hot. I'll check the coolant supply from the engine bay side just in case. And thanks to everyone so far... more ideas, if any, are welcomed of course ))