2017 Denali clogged AC drain tube

Ianwelch001 · June 16, 2017

This is the second time I've had leaking water in my new 2017 Sierra Denali. First time was the xm antenna and now it's looking like a clogged AC drain. Noticed steam coming from the AC vents then looked on the passenger floor and my rubber floormat was soaked. Then turned the AC to floor position and I got a waterfall. Dealership is going to take care of it on Monday because I need the truck to tow my boat this weekend. I'm happy I have the all weather floor mats. Not a drop of water on the carpet.

Can't believe the AC drain tube would be clogged with only 8k miles on it.

michigan2500hd · June 16, 2017

That is hard to imagine. Maybe it was always that way? I have a very noticeable mildew smell when I turn the a/c off. Lasts for a long time after and I even try to turn it off and dry it out for miles before I park it. Just send like common sense to me. First time it happen I had several people in the truck and turns out we all thought someone had farted lol.

Sent from my E6810 using Tapatalk

Ianwelch001 · June 16, 2017

dasimmon · June 16, 2017

at only 8k miles?? wow.

Thomcat · June 16, 2017

Problem is not the water on the carpet, it's any unseen water behind the carpet. Make sure they pop the door sill plate and check the wiring channel on the drivers side for flooding and insulation under the driver's carpet. Get some of those wiring connectors wet and when they oxide will send false resistance signals to the BCM & ECU with unexpected results.

O_J_Simpson · June 16, 2017

I bet it is not a clogged drain line. Check the crush seal and heater core.

truckguy82 · June 16, 2017

I bet it is not a clogged drain line. Check the crush seal and heater core.

This, hvac drain lines clog because over time mildew builds up in standing water. Even if you drain line was 30 feet long with several upward and downward slopes, it would not get clogged like that in 8000 miles on a brand new truck. No way.

Btw, a trick some people do with hvac is simply hook up a shop vac to the drain line exit

Thomcat · June 18, 2017

I bet it is not a clogged drain line. Check the crush seal and heater core.

Easy enough to find out........run the A/C at full with the windows open to generate maximum condensate and see if it drips onto the pavement below. If it doesn't drip onto the pavement after running about ten mins - blocked drain

BTW - same place mine ran out in the Avy when the sunroof drain locked and the sharkfin seal leaked. Hose on sunroof seals first, then try the sharkfin seal.

Ianwelch001 · June 19, 2017

Thanks. Had the shark fin seal done last month when it started leaking at the sun visor

Like_A_Rock_Bottom · May 13, 2018

On 6/16/2017 at 2:29 PM, truckguy82 said:

hvac drain lines clog because over time mildew builds up in standing water.

Btw, a trick some people do with hvac is simply hook up a shop vac to the drain line exit

Hi, everyone. Sorry to revive an old thread, but I recently got a 2014(.5) Silverado that has a vinegar-y smelling a/c when first starting to blow. I read that it's most likely mildew. I tried one method of running the air on maximum heat for a while to see if that would "cook" the mildew before trying other methods. This did not work.

Where exactly would I find the drain line in this truck? I've not found a good source on youtube for this particular model year range of GM trucks.

Any help would be appreciated.

Thanks! Great forum, btw! Been checking out a few threads on various topics, but decided to sign up.

KD88 · February 6, 2020

I have a 2015 gmc SLT Denali .... I noticed water damage on the headliner from the windshield to the Start of the back window all on the drivers side.... water tested Everything ! Sunroof , shark fin, windshield , roof rails.... all perfect... I started removing the headliner from the drivers seat didn’t find the source ... moved to the captains seat behind the drivers side removed the plastic panel where the seat belt comes out then pulled the headliner down...... BAM!! Pool of water!!! The rubbing tube that connects to the AC to drain out was completely disconnected! I thought it was an exterior leak because it had been raining.... but once I noticed water damage the whole way down that side and some old and dry and some wet I decided to remove the headliner enough to peak in.... !!

Edited February 6, 2020 by KD88

JimCost2014 · February 6, 2020

1 hour ago, KD88 said:

I have a 2015 gmc SLT Denali .... I noticed water damage on the headliner from the windshield to the Start of the back window all on the drivers side.... water tested Everything ! Sunroof , shark fin, windshield , roof rails.... all perfect... I started removing the headliner from the drivers seat didn’t find the source ... moved to the captains seat behind the drivers side removed the plastic panel where the seat belt comes out then pulled the headliner down...... BAM!! Pool of water!!! The rubbing tube that connects to the AC to drain out was completely disconnected! I thought it was an exterior leak because it had been raining.... but once I noticed water damage the whole way down that side and some old and dry and some wet I decided to remove the headliner enough to peak in.... !!

I am lost here, are you working on an SUV, or truck?

And welcome to the site.

Edited February 6, 2020 by JimCost2014

KD88 · February 6, 2020

2 hours ago, JimCost2014 said:

I am lost here, are you working on an SUV, or truck?

And welcome to the site.

Hi sorry yes it’s an SUv I also have 3 trucks ford and GM. My Denali has the roof AC vents in the second row. I’ve been hunting reason to explain the random roof leak... I’ve seen shark fin , roof rails , and sunroof after all those checked out just fine I still tore it apart only to find it was a tube from the AC disconnected cause the leak! E water drained all the way up to the windshield. Maybe this could be an issue with trucks with AC systems running behind the headliner.

JimCost2014 · February 6, 2020

37 minutes ago, KD88 said:

Hi sorry yes it’s an SUv I also have 3 trucks ford and GM. My Denali has the roof AC vents in the second row. I’ve been hunting reason to explain the random roof leak... I’ve seen shark fin , roof rails , and sunroof after all those checked out just fine I still tore it apart only to find it was a tube from the AC disconnected cause the leak! E water drained all the way up to the windshield. Maybe this could be an issue with trucks with AC systems running behind the headliner.

Don't think there should be any AC lines in the roof of any trucks. No ceiling/roof vents or cooling system for the rear like the SUV's.

Looked like an SUV, our Tahoe has the same setup, works great to cool our 4 huskies down.