That's a fix for a different problem. It addresses the blend door that determines temperature. Mine is having difficulty sending air to the correct vent. The air temps are fine.

Mark

Sent from my SM-G986U using Tapatalk

 

I find mine always starts on defrost as well. It will stay there for like 30 seconds or so and then move to where it wants. I figured they were doing it to keep from blasting you with the wrong temp air until the jeep had time to either get the ac pump going or build some heat.

 

I find mine always starts on defrost as well. It will stay there for like 30 seconds or so and then move to where it wants. I figured they were doing it to keep from blasting you with the wrong temp air until the jeep had time to either get the ac pump going or build some heat.

Are you suggesting the problem is my patience, and not the vehicle?

You might be right, though I could swear it behaves differently than a year or two ago. I tried it today on a 6 mile ride into town, and it behaved normally in Auto mode.

I'll simmer down and try it for a few days. Perhaps I've just gotten wound a little tighter as I've gotten older.

Mark

Sent from my SM-G986U using Tapatalk

 

The control unit has some fancy electronics and it can lose calibration. The fix might be replacing the control unit, it’s easy to swap. I got the cheaper, non auto, non rear window defrost version. In Florida I never will need defrost, and I always want ac on pretty high... so saved $60.

 

So a buddy who recently got a ‘13 JKUR has this exact issue. My ‘12 JKUR doesn’t have the auto HVAC feature (I ordered it to spec without this on purpose) but at one point or another I think I’ve had this issue.

Either way, did anyone ever determine what the source of this was? Is that control unit (for the auto one) the fix? Or is there a calibration method?

 

This is for a manual AC, but the same probably applies to auto AC.

When the key is turned to ON and the vent mode knob is turned to the furthest counterclockwise position (face vent), the vent mode actuator looks like this:

With the key still turned ON and the vent mode knob is turned to the furthest clockwise position (defrost vent), the vent mode actuator looks like this:

When the key is turned OFF, after about five minutes, the vent door mode actuator is moved to the following position, without any input from the driver:

So, whenever you turn the key back ON later that day, or perhaps tomorrow, the vent mode will not be in the same position that it was when you turned the key OFF. It moves to a certain default (rest) position, which appears to be somewhere in between the defrost and face vent mode position.

 

Great insights! Any thoughts how I can make certain it's the vent mode door actuator and not the control knob?

 

Great post!!!! I have wondered for years what that sound is after I shut the Jeep off. I think I have avoided the issue for mine because I turn the HVAC off after every time I turn the car off, I don’t know.

Either way, I bet this is a good place to start. Thanks!

 

Keep in mind, the sound you hear almost immediately after turning the key OFF is the recirculation mode actuator. It moves almost right away to a default (rest) position. It takes about five minutes for the vent mode actuator to move to its default (rest) position. I didn't look at the blend mode actuator.

 

Turned on JScan and messed around a bit. The vent mode doore actuator is called “Front Mode 1 Actuator.” I monitored three settings, as seen below:

Key ON, engine OFF (engine could be on, but I was in the garage with garage door closed, so not trying to kill myself).

I turned the vent mode knob to the full counterclockwise position (face vent position). This is a target position (and, if the door actuator is working properly, an actual position) of 0. The result:

I then turned the vent mode knob to the full clockwise position (defrost vent position). This is a target position (and, if the door actuator is working properly, an actual position) of 100. The result:

I then turned the vent mode knob to the center/middle position (floor vent position). This is a target position (and, if the door actuator is working properly, an actual position) of 51. The result:

That was at 11:16 PM. I then turned the vent mode knob to the full counterclockwise position, actual and target position 0. I then turned the key to the ACC position so the DLC would still power the Bluetooth dongle and JScan would still operate and monitor the mode actuator. I then went upstairs.

Six minutes later, looking at my phone, the value changes from actual and target position 0 to actual and target position 51. In other words, at rest, the actuator will stop at a default position of the floor vent.

 

I'm back to trying to fix this, as I plan to sell the jeep and this is the only thing not working correctly. @H3br3wHamm3r's post above is very helpful, but I think it's telling me the door actuator is working correctly. If the default position is the floor vent, but mine always starts (and remains, without user intervention to select the dash vents) on defrost, then either the actuator is not returning to the default position, or is being commanded to move to defrost on startup. Since it will move to the floor vents, even automatically when in auto-temp mode, that seems to suggest the actuator is fine, but the commands it is receiving are suspect. Does this make sense? Absent any argument to the contrary, I'm planning to order the auto temp control linked at the top of this thread and see if it fixes the issue.

Mark

 

Keep an eye out for any other electrical weirdness. Like switches activating things they shouldn't, Speedometer showing higher/lower than actual speeds. A malfunctioning alternator will make the electrics go crazy in any vehicle.