Nissan Armada & Infiniti QX56 Forums banner

Rear heater problem - cold air only

44K views 32 replies 10 participants last post by  Birdhouse 
#1 ·
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
 
#2 ·
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.
 
#4 ·
When the rear is set to heat does any air blow from the floor vents?
 
#6 ·
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.
 
#8 ·
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?
 
#9 ·
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.
 
#10 ·
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 ))
 
#27 ·
Vlad's heater, save the 1k



Ok Vlad, no component related to the front heater has anything to do with the rear heater. No "good cleaning" or "servicing" for 1k or any other amount will resolve the rear heater issue you are having. You could possibly have an air pocket in the rear heater core, or a damaged air mixture door. I am still dealing with a customer's rear heater and can share some pictures with you to help you figure out where your problem lies. Let me know if you are interested.
 
#11 ·
I think I may have the same problem. Everything was working fine until my wife bought a dvd deck from walmart and had it installed. SMH... Only thing I notice was that I could no longer control the radio from the steering wheel. I didnt bother checking the rear knobs till 1 year later when I sat in the back and started messing around with the ac. The 2nd row ac-knobs can only adjust the speed. All other 2nd row knobs didnt work. In the front below the stereo theres a knob that you can use to control the rear ac. Turn it to the left, it blows on your feet. Turn it to the right, it blows from the top. That very same knob also controls the temperature. Turn it to the left it blows hot air. Turn it to the right, it blows cold air. I need the heat for this cold weather. but the heat only works for the feet.(knob turn to the left) Now I hear a clicking sound coming from behind the dash. it only clicks after I start the car.
 
#15 ·
I think I may have the same problem. Everything was working fine until my wife bought a dvd deck from walmart and had it installed. SMH... Only thing I notice was that I could no longer control the radio from the steering wheel. I didnt bother checking the rear knobs till 1 year later when I sat in the back and started messing around with the ac. The 2nd row ac-knobs can only adjust the speed. All other 2nd row knobs didnt work. In the front below the stereo theres a knob that you can use to control the rear ac. Turn it to the left, it blows on your feet. Turn it to the right, it blows from the top. That very same knob also controls the temperature. Turn it to the left it blows hot air. Turn it to the right, it blows cold air. I need the heat for this cold weather. but the heat only works for the feet.(knob turn to the left) Now I hear a clicking sound coming from behind the dash. it only clicks after I start the car.
Snizzle, Ntrddragn is right, you said you get heat from the rear floor vent - that how its supposed to work: hot air only for the feet, cold only from the overhead. But the clicking front actuator you have and the cords left disconnected need to be fixed of course.

My problem I started this thread with is COLD air from the rear floor vent, which isnt right and which I'm still working on. Meantime I also have the clicking actuator in the front which wont let the front feet/windshield modes operate properly, but luckily I have hot air there, so no big issue. I have the new actuator, just looking for a moment to replace -there's a link above on p.1 of this thread to Titantalk with clear instructions and pics inside, check it out you might find a solution to your problem actuator in that discussion.

I guess these nissan heaters give a hard time to many owners all over the world :mad:
 
#13 ·
Yes...That is correct. I pulled the indash panel out and saw a few plugs hanging. These plugs is supposed to connect to the back of the stock HU. Im not sure if these plugs are for the cd changer or if its part of the ac. I'll have it checked out when I update the stereo.
 
#16 ·
May be same issue I have.

Hi there, was looking for answer to current issue I have and may be having same issue u are having. To start, forget everything you have been told. Here is how system works: hot coolant comes out of passenger side head, thru water valve that cuts off coolant to inside so truck only when a/c is on full cold, then goes to tubes at firewall where they split to heater cores. 2 tubes run down outside of firewall and under truck on passenger side to rear heater core. With truck warmed up, the tubes should be hot. Note, u have 4 tubes;2 for a/c & 2 for heater. Behind right rear tire u will see the 2 going to heater core, check there to for heat. If neither is hot with warm engine running, then u have no warm coolant flowing out of cylinder head. Same issue I am having. U can still have front heat. Check that and post your findings. Let me know what u find. I will check for post. Which state r u in?
 
#30 ·
Hi there, was looking for answer to current issue I have and may be having same issue u are having. To start, forget everything you have been told. Here is how system works: hot coolant comes out of passenger side head, thru water valve that cuts off coolant to inside so truck only when a/c is on full cold, then goes to tubes at firewall where they split to heater cores. 2 tubes run down outside of firewall and under truck on passenger side to rear heater core. With truck warmed up, the tubes should be hot. Note, u have 4 tubes;2 for a/c & 2 for heater. Behind right rear tire u will see the 2 going to heater core, check there to for heat. If neither is hot with warm engine running, then u have no warm coolant flowing out of cylinder head. Same issue I am having. U can still have front heat. Check that and post your findings. Let me know what u find. I will check for post. Which state r u in?
Infinitymastertech. I am having same problem. One line to rear heater core gets warm. Definitely not hot. The other stays cold. Content figure why I am not getting any ciculation to the core. Did you figure it out?
 
#17 ·
If the rear heater lines are hot at the rear wheel opening then the rear air mix door is stuck in the cool position.
 
#21 ·
The air mix door is inside the rear unit (behind the trim back by the right wheel well). It is driven by the air mix door motor (see attachment).
When the rear heater is in operation, the temp is controlled by the door, mixing hot and cold air. There is a feedback sensor to tell the control unit the position of the door.
Remove the trim to get to the A/C/Heat unit and yow will see the air mix door motor. There are several wires connected to the motor unit.
Whit the rear heater on, adjust the rear temp setting from minimum to maximum and back. Do this several times. The motor should run, and move the door. If the motor doesn't run, check the voltages on the gray wire with the red stripe, and also the blue wire with the yellow stripe. As you change the temp setting up and down one of these wires should measure 12 volts to ground when raising the temp. the other when the temp is lowered.
The yellow wire should shoe 5 volts; the purple wire ground and the red wire with a yellow stripe will read between 0 t0 5 volts if everything is OK.

If all voltages are OK, then you have a bad motor or a stuck door. You can remove the motor unit to see if the door is stuck.
If the voltages are not OK then you have a wiring problem or a bad A/C control unit.
 

Attachments

#33 ·
Ok,there is only one actuator in the rear heater assembly that controls both temperature and air flow. If you set the temp to cold, the air should discharge for the roof vents and if the temp is set to hot , the air should discharge
From the bottom discharge. If the air flow changes that means the actuator is working and the problem is inside the air box. More than likely, it is the actuator.
It is either not working because it is not getting either power or ground. Check it out and post your findings and I will follow up from there. Good luck!

Thanks. I just discovered I have this issue. Plenty of heat in the front, but none in the rear. Going to have to do some detective work in my free time.
 
#23 ·
MAN.....I feel like a suckah...lol Thats good to know.... thanks guys. I thought the Armada rear air is the same as the rear air in my van. My van has no problem with heat from the ceiling vents..
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top