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My heater seems to blow cold on the driver's side and "luke warm" on the passenger side

Tiny
SHASKINS
  • MEMBER
  • 2002 DODGE RAM
  • V8
  • 4WD
  • AUTOMATIC
  • 100,000 MILES
My heater seems to blow cold on the driver's side and "luke warm" on the passenger side. I have pressure tested the system and there does not appear to be any coolant leaks. Also, I have pressure filled the cooling system numerous (6?) Times. Each time it seems to work better for a little while, then goes back to not working well and blowing cold on the drivers side.

Any thoughts? I would have thought blend door problem, but that doesn't make sense that it works better after pressure filling. Is it possibly that heater core is just too clogged and not "flowing" well enough to where only air directed to passenger side gets warmed?

I should note that I have the single zone climate control (no dual zone) and it is the 4.7L engine.
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Wednesday, February 10th, 2010 AT 11:56 PM

11 Replies

Tiny
2CARPRO JACK
  • MECHANIC
  • 11,533 POSTS
If they share a common plenum, there shouldn't be any reason for it to be cooler on one side. Check the heater hoses to be sure they are both hot with engine warmed up, you may indeed have a flow problem keeping the system from getting hot
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Friday, April 23rd, 2021 AT 10:36 AM
Tiny
SHASKINS
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  • 5 POSTS
THese are the heater hoses going to the firewall from the engine/radiator? I should just reach down and feel them while the engine is warmed up?

What would you recommend if they are hot vs not hot?

Thanks,
Scott
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Friday, April 23rd, 2021 AT 10:36 AM
Tiny
2CARPRO JACK
  • MECHANIC
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Yes, those hoses. They wont be scalding hot, just tap them first to see how hot. If the engine is up to running temp, the hoses should both be hot, if not you may have a flow problem with the heater core
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Friday, April 23rd, 2021 AT 10:36 AM
Tiny
SHASKINS
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  • 5 POSTS
I checked the hoses and they seem to be hot after the engine has been warmed up. Not sure how hot they should be, but very warm to the touch after a couple of seconds.

Since the hoses are hot, does that imply a problem with blend doors or actuators? Also, I noticed that it seems the air blow a little stronger on the driver (cool) side as well.

If blend doors or actuators, is that a part that I can readily get?

Thanks,
Scott
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Friday, April 23rd, 2021 AT 10:36 AM
Tiny
2CARPRO JACK
  • MECHANIC
  • 11,533 POSTS
Yes, the parts are readily available, its usually access to them that is the problem. Some may require teh entire dash to be removed to get to them. Try going from hot to cold with temp selector, you should hear a noticeable change in sound of air flow, if not the blend door actuator may be bad, not moving from the a/c evap core to the heater core. If there are any issues with vent selection, the mode door actuator could be at fault
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Friday, April 23rd, 2021 AT 10:36 AM
Tiny
SHASKINS
  • MEMBER
  • 5 POSTS
Interesteingly enough, it seems that the air goes from hot to cold and changes location (floor, defrost, vent, etc.) With no problems.

The only "problem" with the system is that the drivers side blows cool and the passengar is warm.

Could this still be a blend door?
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Friday, April 23rd, 2021 AT 10:36 AM
Tiny
2CARPRO JACK
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Not likely. Check the ducting under the dash. Did this just happen all of the sudden?
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Friday, April 23rd, 2021 AT 10:36 AM
Tiny
SHASKINS
  • MEMBER
  • 5 POSTS
No. It was not all of a sudden. There seems to generally be airflow and it will direct air to the right vents (defrost, vent, floor, etc.) When changed.
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Friday, April 23rd, 2021 AT 10:36 AM
Tiny
2CARPRO JACK
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If it is all good mechanically, you may need to get under the dash and give a real good visual inspection to see if something came loose or is obstructiong the flow from the heater
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Friday, April 23rd, 2021 AT 10:36 AM
Tiny
GOOBERS_GARAGE
  • MEMBER
  • 1 POST
It most likely is a temp blend door problem.

Check out heatertreater. Net
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Friday, April 23rd, 2021 AT 10:36 AM
Tiny
2CARPRO JACK
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Thx
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Friday, April 23rd, 2021 AT 10:36 AM

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