What did you do to your NNBS GMT900 Tahoe/Yukon Today?

[Doubeleive]

Looks like my 4-year-old AGM in my 2007 is starting to talk to me. When I start it in the AM when it's cold, the climate control has started defaulting to 74º on both sides, and 'Auto' is turned off. Best guess is that the battery voltage is dropping overnight. Gonna get a volt meter on it tomorrow to find out for sure.

check it in the morning at the battery post's before you start it up. that gives you resting voltage.
gm's magic number is 10.5v or less. I believe 10.8v is bottom of the barrel for a agm
not sure at what voltage the hvac loose's memory I assume 10.4v or less based on what the I have been told about the 10.5v by the service manager.
so if your battery is super low and then you start it the voltage is going to drop momentarily even more causing either loss of memory functions or even a bad handshake between various modules possibly throwing other codes.....
if it's not the battery then maybe a funky ground or the cold overnight is causing something to shrink/expand and loosing connection which could range from a fuse to a board

 

[gooffeyguy]

My vote is shrinkage from the cold

It happens

 

[Geotrash]

check it in the morning at the battery post's before you start it up. that gives you resting voltage.
gm's magic number is 10.5v or less. I believe 10.8v is bottom of the barrel for a agm
not sure at what voltage the hvac loose's memory I assume 10.4v or less based on what the I have been told about the 10.5v by the service manager.
so if your battery is super low and then you start it the voltage is going to drop momentarily even more causing either loss of memory functions or even a bad handshake between various modules possibly throwing other codes.....
if it's not the battery then maybe a funky ground or the cold overnight is causing something to shrink/expand and loosing connection which could range from a fuse to a board

Checked it this evening and it's already down to 11.8v after sitting since this morning. I'll check it again in the morning.

 

[Doubeleive]

Checked it this evening and it's already down to 11.8v after sitting since this morning. I'll check it again in the morning.

well ya that's not good....
checked the alternator?

 

[89Suburban]

Replaced my 4WD switch, b/c I was getting intermittent Service 4WD errors. We'll see if this was the issue.

More cool: I installed a cheap-o Amazon Android 12 head unit.
View attachment 419437

Everything I've tested so far works. Most importantly is the Android Auto connection, which is automatic, and makes my wireless charger in the center console not useless when needing navigation.

-bZj

Yo you got a link for this? @Down8

 

[Doubeleive]

My vote is shrinkage from the cold

It happens

we can't all be growers

 

[George B]

Having trouble with the recirculate door. It isn’t closed all the way and leaks. Heidi had cold feet for our trip. Maybe the actuator is messed up?

 

[89Suburban]

Having trouble with the recirculate door. It isn’t closed all the way and leaks. Heidi had cold feet for our trip. Maybe the actuator is messed up?

Does the recirculating work for heat? I thought it was for ac only?

 

[George B]

Does the recirculating work for heat? I thought it was for ac only?

No, but cold air pours in from over there on the passenger side and I get a dtc for that actuator feedback circuit so I assume its not closing.

 

[George B]

Having trouble with the recirculate door. It isn’t closed all the way and leaks. Heidi had cold feet for our trip. Maybe the actuator is messed up?

Tech2 can command full open and closed. Closed or outside air measures 30 counts. I did a calibration and didn’t receive the feedback code this time. Going to need to go for a drive. I wonder if I can see that through the panel opening or if the air bag needs to be out.

 

[Doubeleive]

Having trouble with the recirculate door. It isn’t closed all the way and leaks. Heidi had cold feet for our trip. Maybe the actuator is messed up?

If it is only the passenger side then it is likely the passenger side actuator not recirculation otherwise you would get cold feet as well (I think) I don't think it has a separation for left/right but it might.
Try forward heat to confirm passenger side not working or not, use a thermometer to check both sides

 

[Doubeleive]

V1 has left the chat
She had a good life around 10+ years I think, thankfully flat rate repair is only $45 including return shipping.

 

[George B]

If it is only the passenger side then it is likely the passenger side actuator not recirculation otherwise you would get cold feet as well (I think) I don't think it has a separation for left/right but it might.
Try forward heat to confirm passenger side not working or not, use a thermometer to check both sides

I will confirm temps but we do have heat blowing on that side, on the floor and cold air pouring out of the lower cover for the HVAC assembly right below the glove box.

 

[Doubeleive]

I will confirm temps but we do have heat blowing on that side, on the floor and cold air pouring out of the lower cover for the HVAC assembly right below the glove box.

but no cold air on the floor of drivers side?

 

[George B]

but no cold air on the floor of drivers side?

Right. I have heat blowing but no cold air pouring in. Its like the recirculate door isn’t closed all the way and cold air is pouring in at highway speeds. When driving slower there is no cold air leak.

 

[George B]

@Doubeleive
I found this.

https://static.nhtsa.gov/odi/tsbs/2013/SB-10063049-2273.pdf

 

[Doubeleive]

@Doubeleive
I found this.

https://static.nhtsa.gov/odi/tsbs/2013/SB-10063049-2273.pdf

I bet that's the problem and not the recirulation door/actuator
not sure what you have to do to lower the whole glove box, when you have it open there is a little tab to drop the door down beyond that not sure. Might have to pull the passenger air bag (maybe) to get access from above it.
someone else did it or had it done but it's been a while no idea who

 

[Doubeleive]

you could maybe verify by putting it on front air, and defrost. this cut's air to the passenger side. if you still have cold coming in then it's probably the box leaking.
just guessing though

 

[George B]

I bet that's the problem and not the recirulation door/actuator
not sure what you have to do to lower the whole glove box, when you have it open there is a little tab to drop the door down beyond that not sure. Might have to pull the passenger air bag (maybe) to get access from above it.
someone else did it or had it done but it's been a while no idea who

I went out and looked at it. I opened and lowered the glove box and can see a horizontal but slightly angled case joint right above the blower housing. It is on the cold outside air side of the blower. Thats a good 8” long joint with a screw at each end. I will get some sealer and try sealing it up to see if the problem goes away. It’s sleeting out tonight and it’s parked outside. I want it clean and warm for this repair so it sticks.

I also actuated the recirculate door and can confirm its movement.

 

[George B]

you could maybe verify by putting it on front air, and defrost. this cut's air to the passenger side. if you still have cold coming in then it's probably the box leaking.
just guessing though

I could try that. I have to have her drive while I check it out.
I can confirm the source of the cold air is not from the floor outlet. I can feel the hot air blowing out there. I can also feel the cold air pouring in further out towards the door. The glove box is also cold. I bet it’s that case leaking.