I've got the same problem. Oddly enough when I move the controls to "defrost", the air is cool, move it to "vent" and the air is warm... almost humid. Just noticed it today where the air temp is quite cool, but the temp in the truck is warm.

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2005 Ram 1500 QC Hemi SLT

 

Just remember that when you put the HVAC in defrost mode, you actually engage the A/C. The A/C engages to dehumidify the air to eliminate fogging that might be occuring on the inside of the windshield. The A/C operation chills the air enough to overcome the heat added by the blower motor resistor.

Roger...

 

Not sure what you guys are experiencing the descriptions of exact conditions play a lot on many factors. If your vehicle sets in the sun with the windows up for even a short period the inter core temp of the vehicle will rise considerably. This is called “heat soak�. Cooling off the heat soak in the bowels of the dash board/firewall area will take a lot of time without the A/C running. And even a while with the A/C on in the hot months. The core of the dash area houses the heat and A/C, insulation, carpeting and all kind of things that will “hold" the heat. All of your outside air will pass through this before it reaches the cabin inside. I would expect 10 degrees or more above outside temp to be about normal this time of year. Also stopping and turning off the truck for a while will send heat from the engine into the firewall/passenger area.

There could be a problem with an air temp flap, but what you are describing sounds about normal for the summer time and today was officially summer! I can’t see the A/C drain to be causing the problem either. As stated “After fixing the A/C drain problem, I was still encountering warm air from the vents sometimes 8-10 degrees warmer than the outside air.� You should not need additional heat shielding to the HVAC box either.

I can also say that I don’t think the blower fan resistor is the culprit. They have been installing those in heat/A/C plenums for years on many other makes and models.

When I operate my truck during moderate temps that don’t require A/C I crack a few windows and set the fan to blow out all of the warm air for a while. Also makes a huge difference if it has been setting in the sun or shade no matter what time of year.

I have vent shades on the door windows and almost always leave the drivers window down about an inch or so, all year round. This helps a little in reducing heat build up but will not cure it.

Good luck, but it doesn’t sound like you have a real problem. You can always just hit that little button and turn the A/C on.

 

The heat gain from the blower motor resistor is around 10F over the outside air temperature at night when outside air temps are 60F or higher. Next time you have a few minutes, try removing the BMR after 30 minutes or so of operation--it has just a few screws holding it in. Be careful, it's super hot and will burn you badly. The thing is easily 3 inches long and 1 inch square. It puts out so much heat that it warms up the bottom of the HVAC unit noticeably after you've stopped the vehicle--again doing this at night time eliminate the solar heat gain from the equation.

Looking over my other vehicles--Toyota, Pontiac Firebird, Caravan--they seem to have much smaller BMRs or mount them outside the HVAC. I've seen some vehicles mount them in the engine compartment. Unfortunately, when mounted outside, they tend to corrode and fail which probably explains why they're often mounted in the HVAC.

The main lesson is that there is nothing that can be done about the heat gain. We need to hit the A/C button even when it's in the 70s. I had hoped to avoid the MPG hit that occurs when using the A/C, but such is life.

Roger...

 

Can someone tell me why the two drivers side vents are cooling to 40 degrees whiles the three passenger vents are only cooling to 46 degrees? Oh, and the defrost vents are at 60. The truck is at the dealer and just had the condenser replaced. It's an 03 QC 4x4 with only 30k miles, 38 months old - JUST OUT OF WARRANTY!!! [:@]

 

the air travels through the engine compartment and it is warm so no the air is hot


-sal