Front heater cold air

Tiny
PIPERPUP
  • MEMBER
  • 2007 JEEP COMMANDER
  • 5.7L
  • V8
  • 4WD
  • AUTOMATIC
  • 150,000 MILES
I have hot water going into and out of the front heater core connections at the firewall. Rear heat, on the same plumbing, works fine. I have removed both left and right blend door actuators and manually move the doors to both extremes. Nothing but cold air comes out.

I have not used the heater since the core was replaced two years ago as I was living in Florida. Back in Alaska now and heat would be nice!

At this point I fear I need to remove the dash to see what is wrong. Coolant is full, engine temp is normal, and the blower fan seems to have adequate airflow. I sure would like a simple fix if you have one!
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Monday, December 2nd, 2019 AT 6:51 PM

12 Replies

Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi,

If you manually moved the blend air doors and no heat comes out, you need to recheck the heater core. Air flow is directed either through or around the heater core. This is done by adjusting the position of the blend-air door. My first suspect would have been the actuators, but you indicated they were checked. That only leaves the heater core. If you could, recheck flow through the front heater core. Confirm the hoses are not just getting warm from the engine compartment. If you are certain there is flow, then something is preventing air flow direction or the blend door from working. I attached a pics below of actuators. Confirm those are the ones you checked.

Joe
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Monday, December 2nd, 2019 AT 9:02 PM
Tiny
PIPERPUP
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Joe,

Those are the two actuators I removed and the blend doors moved freely stop to stop. I also know hot water is flowing through the core. I retired Dodge mechanic told me they had challenges getting adequate water through the front heater core because the straight run past the "t" had less resistance than going through the front core. What he used to do was eliminate the "t". He said to run from the engine outlet to the front core inlet directly. Then from the front core outlet to the rear core inlet. Finally from the rear core outlet back to the return on the engine. I did this and it didn't change anything. I still have rear heat, which means the water has to be passing through the front core as it is plumbed now.
I know it goes against all logic but there it is. I believe it is a parallel type core. If so, is it possible a large portion of it is plugged up but enough open to let water pass to the rear? The rear heat showed 96 degrees today when it was 13 degrees outside.
A little history on the car. The air conditioning died and the problem was traced to a leak in the evaporator coil. They suggested I have them change the heater core while they had the dash apart. I said okay. I have never used the heat after that until a few weeks ago. That was about 2 years back. Another issue from that repair - the AC works great for a while then the airflow slowly warms and dies off until it stops completely. If you shut it off for 5 minutes and start it up again it works for a bit and then dies. Its almost as if the evaporator coil is frosting over, blocking airflow. I hesitate to tell you how many mechanics have tried and failed to fix that one.
Long winded but there you have it. 30 below in a couple more days. Guess I'll be driving my 1983 pickup!
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Monday, December 2nd, 2019 AT 10:38 PM
Tiny
PIPERPUP
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Joe,

One more question if I may. In your diagram, left side, there is an actuator mode door front. What does that one do? I can see any way to get the hardware off without pulling the dash pad.
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Monday, December 2nd, 2019 AT 10:44 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi,

Good Lord! Did you say 30 below? Ugh. You need heat.

Based on how you have it plumed, it has to flow through that core for it to be that hot on the rear. As far as there being a partial plugging in the front core, you would at least get some heat. Now, you moved the doors manually and it made no difference. Something had to have been put together wrong.

Additionally, the mode actuator is what is responsible for air flow direction. It does nothing with temp.

At this point, you have done everything right. However, what is next? Here is what I would do. There is a cover over the heater core and tubes. Remove the cover, confirm the heater core is hot, inspect blend air door function (actually see what is happening), and hopefully, there will be an answer. I'm starting to question if something was put in backwards such as one of the doors. Something is blocking the heat.

_______________________________________

Here are directions for removal of heater core. You won't need to complete the entire list. Just go far enough to see what may be happening.

______________________________________
2007 Jeep Truck Commander 4WD V8-5.7L VIN 2
Front Heater Core - Removal
Vehicle Heating and Air Conditioning Heater Core Service and Repair Removal and Replacement Front Heater Core - Removal
FRONT HEATER CORE - REMOVAL
REMOVAL

WARNING: Refer to the applicable warnings and cautions for this system before performing the following operation. Failure to follow the warnings and cautions could result in possible personal injury or death.

WARNING: Disable the airbag system before attempting any steering wheel, steering column, or instrument panel component diagnosis or service. Disconnect and isolate the negative battery (ground) cable, then wait two minutes for the airbag system capacitor to discharge before performing further diagnosis or service. This is the only sure way to disable the airbag system. Failure to take the proper precautions could result in accidental airbag deployment and possible personal injury or death.

NOTE: Take the proper precautions to protect the front face of the instrument panel from cosmetic damage while performing this procedure.

NOTE: LHD model shown in illustrations. RHD model similar.

Pic 1

1. Disconnect and isolate the negative battery cable.

2. Drain the engine cooling system.

3. If required, disconnect the heater hoses from the heater core tubes in the engine compartment.

4. Remove the instrument panel.

5. Remove the five screws (1) that secure the heater core and tube cover (2) to the HVAC housing (3).

6. Remove the heater core and tube cover from the HVAC housing.

Pic 2

7. If equipped with dual zone heating-A/C, remove the blend door actuator (1) from the passenger side of the HVAC air distribution housing (2).

8. Remove the screw (3) that secure the heater core tubes (4) and retaining bracket (5) to the HVAC housing (6).

NOTE: Take proper precautions to protect the carpeting from engine coolant. Have absorbent toweling readily available to clean up any spills.

9. Remove the bolt (7) that secures the heater tubes to the heater core (8).

10. Disconnect the heater core tubes from the heater core and remove and discard the O-ring seals.

11. Install plugs in, or tape over the opened heater core ports.

12. Carefully pull the heater core out of the HVAC air distribution housing.

13. If required, remove the heater core tubes from the vehicle.

____________________________

You will not be able to see the entire core, but you will be able to touch it to confirm heat and hopefully see if one if the doors is not properly installed.

Let me know.

Joe
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Tuesday, December 3rd, 2019 AT 5:52 PM
Tiny
PIPERPUP
  • MEMBER
Thank you,

I will work on it a bit tomorrow and see what I can uncover. By the way, rock auto shows a heater core for my jeep 'without" dual zones. That implies there are different cores available. Is that true? If so, could they have put the wrong one in?

Thank you again. I will let you know what I find.

Jim
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Tuesday, December 3rd, 2019 AT 7:14 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi,

The core would be the same regardless. Let me know what you find. This has me really interested. LOL

Take care,
Joe
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Tuesday, December 3rd, 2019 AT 7:34 PM
Tiny
PIPERPUP
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Well, I have enough of the dash apart to see the end of the core but that's about it. I did find the occasional coolant smell. The connection to the pipes is not flush at both ends. Slight drip at the bottom. Trying to upload pictures but I may need to go to my laptop to do it.
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Saturday, December 7th, 2019 AT 1:17 PM
Tiny
PIPERPUP
  • MEMBER
I tightened up the fitting and stopped the leak. Ran the car and both the inlet and outlet pipes at the core are hot. The end of the core is hot, but perhaps not as hot as the pipes.

Opening and closing the blend door makes a very minor change in temperature, but not nearly what you would call hot. Keep in mind the car is in a heated garage (70 degrees) as I am doing this.

My thoughts:
1. Air trapped in the core (what genius put the return line on the bottom?)
2. Partially blocked core (minor temp change moving the blend door at 70 degrees ambient air. I doubt you would feel anything with negative 20 degree air entering the system)

Open to any other thoughts before performing surgery on the jeep!

Jim
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Saturday, December 7th, 2019 AT 2:49 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
I agree. What a design. If you suspect there could be an air block, I would try to open the return where it attaches to the heater hose and see if you can get any air from it. But I have to be honest. It's hard to believe air would still be in there after all this time. Are you getting normal air flow? It just doesn't make sense.
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Saturday, December 7th, 2019 AT 9:00 PM
Tiny
PIPERPUP
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Yes, normal air flow from what I can tell. I do not like the idea of throwing parts at a problem, particularly a part that is going to be a pain to change, but I am leaning toward pulling the core.
Running out of ideas but I refuse to let this thing beat me!
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Saturday, December 7th, 2019 AT 9:42 PM
Tiny
PIPERPUP
  • MEMBER
Heat!
I don't understand why it works this way when it wouldn't work the factory way or the way the Dodge mechanic told me to plumb it, but I will take it none the less.

Plumbing is now set up like a Commander without the rear heat option. Engine outlet to front core inlet, front core outlet to engine inlet. I don't have any idea what changed as I had hot pipes, inlet and outlet, the way it was plumbed. Regardless, this is how it is staying for as long as I own the Jeep.

Thank you for the input!

Jim
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Sunday, December 8th, 2019 AT 10:54 AM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Wow. One never knows what to expect. So if I understand, you switched the inlet and outlet? Honestly, in my mind I can't understand what difference that made. LOL

Regardless, if it's working, that's great news.

Joe
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Sunday, December 8th, 2019 AT 7:55 PM

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