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Unwanted heating

My 2005 Dodge RAM ventilation blows heat and seriously reduces the cooling effect of the air conditioner. Is this a common problem, in particular one that I might easily fix myself? Or do I need to take it in for diagnosis and repair and get my wallet out? Mid summer is upon us and I need some relief from the heat.

Yes, yes and yes.

Sounds to me that the blend doors do not properly shut and/or open. Here is a link to a youtube video dealing with something similar.

Two possibilities.

The HVAC controller is faulty,

Or the blend door actuator motor is faulty,


I doubt that it’s an HVAC problem because the air vents on the driver’s
side deliver cool air. It’s the passenger side that appears to lack the
cool air. Perhaps we have a squirrel nest in the ducting somewhere.

Does your RAM have a duel zone control HVAC?


Not recommending this as a solution as it might have adverse unintended consequences, but if it is an emergency situation you might be able to figure out a way just bypass the coolant flow through the heater core until you get the blend doors working again.

This is a RAM pickup, not a RAM van, correct? The vans of that vintage used a vacuum actuated water valve to shut off hot water to the heater core.

If you have no water valve, and you have cool air on the driver side and warm air on the passenger side, I will guess that you are low on refrigerant and the expansion valve is on the driver side of your evaporator. If you have never added refrigerant in 13 years, that would not be surprising, and does not necessarily indicate a serious problem.

How did you determine the HVAC system was blowing heat and not an A/C performance problem? I suppose if the A/C is cooler before the engine warms up this might suggest that you are getting heat.

When the system is low on refrigerant you will get warmer air on one side than the other, acts like a failed blend door actuator on a duel zone system but low refrigerant is much more common.

I have replaced many compressors on the 2003-2006 diesels, slow leaks are common on those. If it is low recharge the system, it may take a couple of years to leak out.

On almost all tractors and school buses I drove had an inine water shut off vale in the rubber hose going to the heater to keep any hint of heat from getting in the cab for the summer.

Wow, thanks for all the helpful comments. I really appreciate it. Especially because the problem now seems to be pretty clearly a low refrigerant level. I’ve never had the refrigerant replaced since buying this diesel truck in 2005, so the weak A/C on the driver’s side and the non-existent A/C on the passenger side seem to point strongly to a low refrigerant level, according to your expert counsel. Thanks again.

Suggest to use an experienced AC shop to confirm the diagnoses, and to add refrigerant (if needed). Modern AC systems get very cranky – and very expensive to repair – if too much refrigerant is installed.

Okay, I used an experienced shop, refrigerant was low, no leaks were found, refrigerant was added, and we ride cool once again!