HVAC not shutting off with truck

Hi all,

Having an odd problem. The aftermarket brake controller in my 2015 came loose and caused all kinds of weird problems(lost steering sensor angle communication, lost wheel speed sensor communication, cruise control not working) that tooke forever to hunt down - all of which I finally fixed by reseating the cable in the back of the controller. There is one problem that remains - the vents don't stop blowing air when you shut off the truck. You don't even need the key in - whatever setting it was on will stay on until you start the truck back up.

Any ideas? Right now I'm leaving the battery disconnected to hopefully reset any weird fault states (there are no stored or pending codes).

 

Maybe shut it off before turning truck off until you can hunt down the gremlin. Weird problem. Maybe a bad relay but strange it still has power after ignition is off.

 

Definitely have to do this to keep it from draining the battery. Closest similar problem I can find is from a first gen where somone replaced the blower motor resistor.

 

Maybe you have a bad ignition switch, acc always on. Pulling fuse might be easier than the battery disconnect.

 

This is usually caused by a bad resistor. Does it turn off when the controller is set to off?

 

Yes, it shuts off when you tell it to when the truck is running. It doesn't shut off if the key is out and you turn the fan speed to off.

All the accessories go off when you turn the truck off, but air continues to blow.

 

@TundraTex I did recently add the FRAC harness - could I have shorted something by accident on your board? Can you think of anything in the harness functionality that would cause this?

Really racking my brain here, this is such a goofy gremlin.

 

K, on these I’m fairly certain the speed controller/resistor and the blower motor are one unit. Most likely a short in one of the integrated circuits. Check for signs of overheating/burned wires at the blower connector. I’m guessing it needs a blower motor assembly.

 

I believe you're correct - looks like one piece. One connector and three bolts under the passenger side dash. No visual problems like frayed or damaged wires , so I'm hinking I'll try popping in a replacement part to see if anything changes.

 

Replaced the blower assembly.

No change.

 

Well that’s no good. Did you check all fuses? According to the diagram, the blower has constant power and is controlled by a signal from the amplifier which receives request from control panel. When the truck is on, the amplifier could send/receive signals because it has an ignition power source. If the amplifier’s “hot at all times” fuse is gone it may lose its ability to control with ignition off. Mostly theory, but if the blower always has power, the amplifier has to control the signal with the truck off too. If all your fuses look good, it may be time to consult a shop. Good luck!

 

Guess you know there is a fuse block under the hood and also one with micro fuses up above parking brake pedal small narrow box way up in there, black cover about 1.5" wide and maybe 5" long

 

Just tested the three fuses in the kick panel from the diagram that feed the A/C amplifier - all fine.

 

I'd consider replacement amplifier

 

Part Number: 886500C321

Maybe I can find one at a pick N pull
I'm seeing $400-$715 for the part, yeesh.

 

Yes I would be at salvage and pulling a few, one for you, two for sale on ebay to get yourself a free one.

 

It’s good to look at all options when gremlin problems arise, but the FRAC Harness only interfaces with the head unit functions so I don’t believe it would be causing this type of problem. And if all the FRAC functions are working, then it’s not fried.

 

Thanks! Just working my way through the things I've done recently and really reaching. I've even tried taking out the speedo calibration at this point hoping for a something.

I guess I am going to put a sticky note on the steering wheel or door handle like my grandparents did, to remind my forgetful self to turn off the fan before shutting off the truck.

 

Ok found it finally. I had hooked up front camera power to the same lead as my nsv light bar out of convenience. For some reason that did not jive well. Still don't understand the logic but oh well, it's fixed. Thanks for the help everyone.