The other day I was driving my 2012 SHO, it was warmed up and heat coming out the vents and suddenly it just started blowing cold air, just like if someone just flipped the setting and turned the AC on (it literally changed in something like 10-20 seconds).  It was in the teens outside, it's been cold.  Both sides are the same temp, once the engine warms up it's not as cold as outside, but I'm guessing its like 30-40*.  Settings don't matter (auto/manual, any set of vents, same or different temps on each side...)

I did some googling and didn't really see anything that matched exactly, a lot of "passenger side cold" and "goes cold at idle or light cruise" (seems to be low coolant).  I checked the coolant (it's fine, looks good, tests good).  The passenger side cold stuff seems to be the actuator but a lot of people report that disconnecting the battery seems to fix it. 

Well it doesn't match but it won't hurt to try.  I disconnect the battery, let it sit for 15min and reconnect.  I take it for a test drive and everything appears to be working once the engine heats up.  I drove it to the gym, to a friend's house, it works fine.  I leave to go home.  No heat again.

Any clue what is going on?

Sounds like a bad climate control module, since disconnecting the battery made a difference.  Check coolant levels anyway when engine is off/cold.  Should be at/above full mark.  Could be a stuck open thermostat. But if the car is running fine and mpg is good, that is probably not it.

Quote from: SHOdded on January 10, 2017, 06:14:27 PM
Sounds like a bad climate control module, since disconnecting the battery made a difference.  Check coolant levels anyway when engine is off/cold.  Should be at/above full mark.  Could be a stuck open thermostat. But if the car is running fine and mpg is good, that is probably not it.

I checked coolant when cold, it's at the right height.

A stuck open thermostat wouldn't allow it to heat up as fast.  It heats up fine.  Like I said, the first time it did it I was literally rolling down the road with heat blasting and it just turned off.  At that point there is nothing that a thermostat could do to that would cause that. 

FWIW, I tried disconnecting the battery again last night and as of right now I have heat and it's still working after driving it 2x. I suspect that a few more times and it will stop again, but we'll see

Likely back to the CCM then.  Have you had the battery load tested (w a digital tester)?

Mine has a mind of it's own.  It's still in "auto" despite the fact that I have auto turned off.  I'll just be driving and get the heat of a thousand suns.

All the tech in this car is pissing me off.  Just give me a knob for a damn blend door. 

Quote from: SHOdded on January 11, 2017, 03:25:47 PM
Likely back to the CCM then.  Have you had the battery load tested (w a digital tester)?

Battery?  No, but it's less than 4 months old and is strong.  Why?  If I was loosing power it would be resetting on it's own.

Quote from: Vortech347 on January 11, 2017, 06:33:31 PM
All the tech in this car is pissing me off.  Just give me a knob for a damn blend door.

Yea, people hear me talk about what this car can do and wonder why I hate the new tech in cars... It's great when it all works, but the second something does something weird it becomes a nightmare.

I had a headlight out on my Cummins Dodge Ram (nowhere near as much tech as the SHO, but everything is controled by computers with busses connecting them).  I get a light bulb and swap it.  NOTHING.  I check for bad sockets/connections, the normal stuff... nothing.  I start checking if I have power from one end to the other... Um, how the heck does this thing work?  I look up a wiring diagram and figure out that the switch in the dash connect to a computer in the dash which uses a single data line to a lighting computer mounted under the fuse box under the hood.  I have to pull the fuse box and a section of the underhood wiring harness to get to the computer, I go to loosen the fasteners holding the computer down and when I grab it and squeeze the case and the headlight that wasn't coming on comes on... uh oh... that can't be good, but I'll just open the case and fix whatever is shorting out and I'll be OK... No dice, the whole inside is potted and there is no way to get to anything without destroying it.  2 days of putzing with it, a week of waiting for a new computer to come in and $900 later I have a working headlight.  Freaking wonderful... They needed to add 2 computers, a bunch of data connections... to work the headlights? 

Makes you really miss replacing $20 headlight bulbs and switches and $5 sockets (which a few years ago were more like $5-10 bulbs and switches and $3 sockets).

Quote from: Silverback on January 18, 2017, 06:07:10 AM

Quote from: SHOdded on January 11, 2017, 03:25:47 PM
Likely back to the CCM then.  Have you had the battery load tested (w a digital tester)?

Battery?  No, but it's less than 4 months old and is strong.  Why?  If I was loosing power it would be resetting on it's own.

Load test the battery anyway.  What battery did you put in it?  Do you keep driver/pass side temps the same?  Does it respond when you change the temps on one side while the heat is working?  I think there is a calibration routine for the FCIM/Climate Control Module, will see if I can dig that up.  Also check coolant level with engine off/cold.  Should be at/slightly above the FULL line in the degas bottle.  Have you opened up the cooling system for any reason, such as replacing a TStat?

It could also be the blend door actuator's.  You have 3 of them and they are known to go out.  I had 2 of the 3 replaced on my 11 SHO.  When it would fail I could have the heat set on 90 and high fan but still get cold air.  With mine it was only 1 at a time that failed so I would have blazing heat on one side of the car and freezing air on the other side.  With the car running, radio off and blower on lowest setting you can normally hear repeated clicking faintly from in the dash.  That was my tell tail sign I had another one fail. I would mess with all the controls, heat up, down blower high, change where it was blowing from and eventually it would work the way I wanted for a few days and then fail again.

Quote from: SHOdded on January 18, 2017, 08:04:47 AM

Quote from: Silverback on January 18, 2017, 06:07:10 AM

Quote from: SHOdded on January 11, 2017, 03:25:47 PM
Likely back to the CCM then.  Have you had the battery load tested (w a digital tester)?

Battery?  No, but it's less than 4 months old and is strong.  Why?  If I was loosing power it would be resetting on it's own.

Load test the battery anyway.  What battery did you put in it?  Do you keep driver/pass side temps the same?  Does it respond when you change the temps on one side while the heat is working?  I think there is a calibration routine for the FCIM/Climate Control Module, will see if I can dig that up.  Also check coolant level with engine off/cold.  Should be at/slightly above the FULL line in the degas bottle.  Have you opened up the cooling system for any reason, such as replacing a TStat?

The battery is from Costco (don't remember right now if they're still doing Kirkland stickered batteries, Interstate or anything else), load tests higher then it's rated CCA.

I haven't had the cooling system opened for any reason (besides the cap on the tank, and that only 2x), shouldn't be any air in the system.

If you can come up with the calibration routine that would be appreciated (hopefully it's something that you can do without any factory scan tool).

Quote from: donky4444 on January 18, 2017, 12:09:23 PM
It could also be the blend door actuator's.  You have 3 of them and they are known to go out.  I had 2 of the 3 replaced on my 11 SHO.  When it would fail I could have the heat set on 90 and high fan but still get cold air.  With mine it was only 1 at a time that failed so I would have blazing heat on one side of the car and freezing air on the other side.  With the car running, radio off and blower on lowest setting you can normally hear repeated clicking faintly from in the dash.  That was my tell tail sign I had another one fail. I would mess with all the controls, heat up, down blower high, change where it was blowing from and eventually it would work the way I wanted for a few days and then fail again.

When it stops working no amount of messing with the controls makes any difference or causes any clicking...  I believe that it's possible that it's a blend door actuator, but for it to have done what it's done multiple times (both sides doing the same thing, both sides reset with the battery disconnect, failed exactly the same and the same results with the battery disconnect multiple times) is likely something like a one in a million shot.

FWIW, Mine hasn't done it since I last mentioned about disconnecting the battery... for now it appears to be working...

Take what you can get, LOL.