‘21 Tahoe - Cold on Drivers Side, Hot Passenger Side

[nmcgrawj]

Hey everyone, trying to see if anyone else is having this problem that my sister’s truck appears to have. 4,000 miles and the HVAC blows cold on the drivers side while hot on the passenger side.

Dealer said the heater core is bad and coolant isn’t flowing which seems odd to me. I figured one of the blend door actuators went bad.

Anyhow, brand new truck and in Michigan so not great timing as the parts are on back order.

Anyone experience anything similar?

 

[OR VietVet]

Welcome to the forum from Oregon

The dealer is full of it. It would not have any warm/hot air if had a bad/clogged heater core and have never heard of a new rig do that, ever.

Sounds like a programming problem or an actuator went bad, unless someone threw something up on the dash that got down in the vent system and is blocking something.

Warranty work in her future.

 

[nmcgrawj]

Welcome to the forum from Oregon

The dealer is full of it. It would not have any warm/hot air if had a bad/clogged heater core and have never heard of a new rig do that, ever.

Sounds like a programming problem or an actuator went bad, unless someone threw something up on the dash that got down in the vent system and is blocking something.

Warranty work in her future.

That’s exactly my thought as well!

What’s frustrating is they took the truck in and had it for less than a day, only to come back and say it’s clogged and they don’t know when they will get the part since it’s back ordered. Seems hard to believe they could get to the actuators under the dash that quick...but maybe they are easily accessible?

 

[OR VietVet]

That means that they know of a group of heater cores that are made defective but I still don't buy that allows one side to be cold and one side hot, unless the new style heater core has two distinct chambers. Make sure you update us as this goes along and make she she gets complete detailed documentation as she goes along. Do not let her accept documentation that says: reason for failed heater core, Bad. Details about what makes it bad.

 

[nmcgrawj]

That means that they know of a group of heater cores that are made defective but I still don't buy that allows one side to be cold and one side hot, unless the new style heater core has two distinct chambers. Make sure you update us as this goes along and make she she gets complete detailed documentation as she goes along. Do not let her accept documentation that says: reason for failed heater core, Bad. Details about what makes it bad.

Yep, that’s my plan. I’ll be sure to keep you guys updated. Hopefully this is a one off failure!

 

[Hrocks]

Tell her to keep taking it back to the dealer for anything that's not right to build a lemon law case. This is another classic case of first model year GM fails.

 

[nmcgrawj]

So Friday morning she went to put it on defrost and the air came out of the front vents.... who would have guessed!

She's dropping the truck off today for them to keep it until its fixed. Should be in a loaner...but so far have only offered a Traverse which seems rather cheap seeing as they don't know how long she won't have the truck.

 

[Doubeleive]

when you drop it off I would seriously ask lots of questions, 1. what made them assume it was a heater core (100% sure that is b.s.) ask them to show you a diagram of how the heater core is designed (then ask a for a explanation, while they stutter and come up with some lame excuse), because it has a left & right blend door and a mode door up/down/defrost and should have one more for re-circulation and 1 heater core in front and 1. heater core in the rear. I have looked under the hood the system is designed the same at it has been for the last 40 years, still has the plastic T's that split off to the rear, there is isn't 4 lines going into the firewall.

 

[RugbyRef]

Sorry to be Captain Obvious here and this could be a dumb question, but is her Tahoe equipped with the "Sync" button? It's on the right-hand climate control panel knob. Perhaps the divers side is set to a cooler temp and the passenger side is set to a warmer temp?

You know...the whole Occam's Razor theory...maybe...kinda?

 

[nmcgrawj]

Sorry to be Captain Obvious here and this could be a dumb question, but is her Tahoe equipped with the "Sync" button? It's on the right-hand climate control panel knob. Perhaps the divers side is set to a cooler temp and the passenger side is set to a warmer temp?

You know...the whole Occam's Razor theory...maybe...kinda?

At first I thought that may be it LOL....but after another few days past and then the dealer also saw the temp difference. The last straw was the air blowing out of the front vents when set to defrost.

I'm in NC while she lives in Michigan...so i'm doing the best I can to support her remotely.

 

[nmcgrawj]

So the final verdict is in....

Turns out the dealer didn't know what was wrong. They reached out to GM and they told them they have seen similar failures before and it was GM that told them the core would be blocked. So once they got the part in, my sister dropped off the truck this past Monday and picked it up today. They say the tech was able to confirm that there were blocked passages in the core. The truck HVAC is running as good as new now.

My only guess is that the new design has separate airways through the core so that if one side was blocked, it didn't warm up. While her car was at this dealer, they got another one in with the same problem.

I hope they identified the manufacturing issue with the supplier and the replacement part she got is actually a good part. I hope not too many other owners have to go through the same thing!

 

[89Suburban]

So the final verdict is in....

Turns out the dealer didn't know what was wrong. They reached out to GM and they told them they have seen similar failures before and it was GM that told them the core would be blocked. So once they got the part in, my sister dropped off the truck this past Monday and picked it up today. They say the tech was able to confirm that there were blocked passages in the core. The truck HVAC is running as good as new now.

My only guess is that the new design has separate airways through the core so that if one side was blocked, it didn't warm up. While her car was at this dealer, they got another one in with the same problem.

I hope they identified the manufacturing issue with the supplier and the replacement part she got is actually a good part. I hope not too many other owners have to go through the same thing!

That's cray cray a blocked heater core hmm.....

 

[Doubeleive]

that is crazy and unless they made additional design changes then when this type of failure happens after the warranty period is up it's going to be one hell of a costly fix. whole dash has to come out to change the heater core. $30 part and $1000 labor or something like that.

***also very crazy that a brand new heater core is getting "partly" clogged up, that shouldn't happen unless there was some kind of contaminate in the system , makes you wonder what else is getting clogged up.

 

[nmcgrawj]

Yea I am interested to actually see the HVAC system box to understand better on how it can cause a hot passenger/cold driver failure.

Reminds me of the recall from Hyundai we were notified of on our Sonata. Cutting chips in the crank oil circuit holes eventually leading to the crank eating itself. Luckily ours didn't fail.

There must have been some production run that had the heater system (and hopefully not entire coolant system!) become contaminated and lead to clogging the heater core.

 

[CptnC]

So the final verdict is in....

Turns out the dealer didn't know what was wrong. They reached out to GM and they told them they have seen similar failures before and it was GM that told them the core would be blocked. So once they got the part in, my sister dropped off the truck this past Monday and picked it up today. They say the tech was able to confirm that there were blocked passages in the core. The truck HVAC is running as good as new now.

My only guess is that the new design has separate airways through the core so that if one side was blocked, it didn't warm up. While her car was at this dealer, they got another one in with the same problem.

I hope they identified the manufacturing issue with the supplier and the replacement part she got is actually a good part. I hope not too many other owners have to go through the same thing!

Just dropped mine off to dealer for same issue today. I hadn’t read this before dropping off, but they’re going with same approach…flush the whole system b/c of “restriction” in the heater core (all day job). I was thinking it was a temp sensor on the driver side or an actuator. I explained when both the driver and passenger controls set to same temp (sync or not) force the fan on high and cycle through the vent options. Out of that center console the left (driver vent) blowing cold, passenger right next to not doing what is should be at 79 degrees (hot). Pattern same for the front defogger and the footwells. So definitely all vents associated with the driver side not putting out the temp the controller says.

 

[Taurus5778]

I have a 21 Tahoe RST and this morning the only way I could get heat on the driver side was to turn it up all the way to 81° or higher on the control. I turned the truck off and restarted it....Now I don't get any heat no mater what I put the control on. I havent called the dealer yet but I will update this post when I find out more.