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
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.
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.
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.
Images (Click to enlarge)
Tuesday, December 3rd, 2019 AT 5:52 PM