Cabin Heat Issues

[Remy_Dog]

With winter and colder temperatures fast approaching, I am finding that when I set the cabin heat to 68 degrees, I'm getting cool, if not cold air. If I set the temp. to 74 degrees the heat gets to be unbearable. The dealer diagnosed a sensor failure (somewhere behind the driver-side dash) and replaced the sensor. There is no difference. I had no problems last winter, and the A/C worked fine through the summer. I've never used the "Auto" feature. Also, after the dealer service the blower seems weaker. I would greatly appreciate any suggestions.

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[DylanM]

The HVAC module will always automatically control the position of the blend doors to try to achieve the set temperature, regardless of whether it's in Auto or Manual mode. It's not like older vehicles where you manually set the blend door position via a knob or slider and that's where it stays until you move it again. As the cabin temp gets closer to the set temp the HVAC module will adjust the blend doors cooler/warmer as needed to best achieve and maintain the temperature; this can manifest itself as air coming out of the vents that you may feel is too cool or too warm. Where the air is coming out, the blower speed, amount of sunshine coming in the windows, and outside weather/temperature conditions can all influence differences in how you perceive the cabin temperature to be and what the HVAC module detects. I'd suggest if the air coming out the vents feels a bit too cool or warm, adjust the set temperature a couple degrees or change the blower fan speed.

As for the blower seeming to be weaker after dealer service, I would check to see if the blower is still working on all speeds, look for anything blocking the air inlet, and verify the cabin air filter isn't clogged/obstructed/incorrectly installed. If nothing obvious is found and you still have a concern, convey that to the dealer that did the service.

 

[Remy_Dog]

@DylanM yes, you correctly describe how the system should function. My JT’s system is malfunctioning as I described above. For example, with an outdoor ambient air temperature of 40 degrees and the cabin heat set at 68 degrees the system shouldn’t be blowing outdoor or slightly above air temperature into the cabin.

 

[DylanM]

For example, with an outdoor ambient air temperature of 40 degrees and the cabin heat set at 68 degrees the system shouldn’t be blowing outdoor or slightly above air temperature into the cabin.

That depends on how warm the temperature is inside the cabin. If the temp inside the cabin is close to 68° already, then it wouldn't be surprising for the vents to be blowing cool air. Maybe try temporarily putting a thermometer inside the cabin near the temp sensor inlet to see if that's the case (it's located behind the small grill in the dash, below the ignition).

 

[Volt0]

Also check/replace your cabin air filter. Fwiw, mine seems pretty inconsistent ( temp wise ) too. A couple of bullets to share:

• Auto works better
• On a cold morning, select a cooler setting; then bump up the temp by a degree or two every 30 min till you reach the desired temp; ex: if you want to end at 72°, then start with something like 65°
• Could be related to the thermostat and/or engine temps
• Design-wise, I find the ACC to be pretty judgmental too, like a switch that’s either on or off, with non-settle transitions

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