ppilotmike

Its getting that time of the year up here that you need a little defrost in the morning. One day I had great heat from the defroster next morning it is cold air only. I removed the glove box and the metal lines leading to the heater core are HOT. So my thoughts are what ever controls the heat in the plenum has craped the bed. Anyone have a similar problem?

Jeepinjim

I have a 13 JKU, I took the acuator off and just pushed on things, put it back on and it worked. You can order a new one off of the Internet for $35, I did that so I would have a spare. It's just 3 screws and it pulls off. Give it a try , it might work

ppilotmike

I read where that fixed your problem in your thread, thanks for letting everyone know what fixed your problem, I tried the same with no change in my problem. I have the three knob control out and will get it checked tomorrow at a dealer I work with. My problem came on very suddenly, one day heat the next nothing from any vent or defroster. I will update this thread as I make progress in getting it fixed. Mike

ppilotmike

Ok I am a little wiser now the I was when this started. The blend door is what controls how hot/cool the air is. It is accessed from the drivers side after you remove a plate under the steering wheel, I think this is the actuator that Jim was talking about. A piece of the linkage was disconnected so I simply reconnected it and I had heat again. As a side note after removing the three knob controller and reinstalling it, the rear window defrost light would blink for a minute or so and then stop after every start, everything worked normal. I took it to my friendly stealer and they hooked it up to their scanner and "reset" the HVAC controls for $45, no more blinking light. I have 27K miles on my Jeep and am starting to get a little disenchanted with all the crazy gremlins it has had, may move on to a different vehicle soon. This concludes this episode of wild and crazy HVACs.

Poseidon_Guy

OK, so my 2011 JKU started with the blinking defrost light after most engine start ups, during that 30 to 60 seconds i had zero hvac functions, not even blowing air. Once the blinking stops, normal AC functions resume....MINUS heat. I can switch between vents, floor, defrost just fine and all blower speeds work, just when i crank up the heat it goes from freezing cold, to semi cold. I switched AC control units with another jeep which was working fine, backflushed my heater core even though both lines get piping hot, t-stat is working as it should and coolant levels were normal......

Don't know if it's just coincidence or caused by this, but it started after i replaced the battery 2 weeks ago.......I'm losing my mind chasing this problem.....anybody gone through my same issue?

Cpeterso87

My experience is that most of the time of the defrost light is blinking and you can't get heat, then it is an issue with the blender door inside the HVAC unit. In mine, after a MAJOR disassembly nightmare, I found a small shard of glass (leftover from when someone broke all the passenger side windows out of the Jeep) had gotten wedged between the leading edge of the blender door and the HVAC casing. Unfortunately, the shaft on my blender door had been broken off by an overzealous service technician at my dealership, but they were unwilling to take on the repair due to all the modifications to my JK. The replacement HVAC unit cost me less then $90, but the disassembly was over 30 hours of extremely nerve-wracking disassembly that included the entire dash assembly, steering column, the center console, the upper intake manifold, the air box, the power distribution unit, and my custom dual battery box. Removing the driver seat also made the work a bit easier. Fortunately the reassembly went fast, completed in less then a day. The only casualties were the heater hoses in the engine compartment that were so thoroughly fused to the heater core tubes that they ahd to be cut off, and the brake light switch that was damaged as I was wrestling the unwieldy (and remarkably heavy) dash unit out of the Jeep.

In my case, the disassembly was complicated by:

1. XM Satellite radio - the antenna wire had to be removed to get the dash out, which was a realy PITA.
2. Dual battery box I have, which made removing the battery box to get to the main wire harness more difficult.
3. Numerous electrical mods which resulted in a lot of extra wiring to deal with as the dash was being removed.
4. Tuffy security center console which is quite a bit more difficult to remove then the stock center console.

On the plus side, some things were made easier:

1. My 4.5" lift and 37" tires, made getting to the various lower bolts for the intake manifold much easier
2. Having taken the upper dash apart numerous times for stereo and electrical mods made me more familiar with that part of the build.

Incidentally, I recommend Do It Yourself and DIY Auto Repair by ChiltonDIY for good service manual for the JK.

Let me know if you need more information.

pazitive44

My buddy has a 2011 JKU w auto temp w the same blinking light problem after 45-60 seconds blower starts working ,
But No Heat ...the Selector knob works correctly ,but temp selector ( hot/cold ) doesn't .
It's stuck in Full Cold mode .
I see the blend motor actuator on passenger side ,but this controls duct position .
I looked at some Mopar schematics and it shows another actuator on driver side .
Will investigate tomorrow .
Has anybody changes the Driver's side
Actuator ?
I will try to manually spin the flapper valve that mixes hot/cold air .

pazitive44

All actuators worked correctly...
Temperature Controller still Blinks then comes on after 45 Seconds.....
The link for drivers side actuator was Off ...
Reinstalled...Now there's Heat !!! Just in time for Winter !!

nosnhoj1

It seems like the blinking light is more common than I thought. My 2014 JKU blinks at start and you can't turn the heat or A/C on until it stops blinking. The most annoying thing is that the A/C defaults to off every time you shut off the jeep so it blows hot air until I remember to push the button to turn the A/C on. Haven't tried the heater yet this year so now I'm wondering if it works like it should.

Asinine

Similar problem here - get the blinking light at every start, and then intermittently it'll default to heat and high fan making the interior miserably hot in a hurry. Usually happens on road trips, say after the 3rd or 4th start of the engine. Dealer reset the dynamic thermocouple radio transducer (blah blah blah) and it's more reliable, but still happens occasionally. Wish I could find a permanent fix, but of course it never happens when I'm at the dealer.