tgsz

It's 100% bacteria and mold in the hvac condenser case - I had the same issue on my 2021 Yukon and now it just started on my 2023. It always happens after a few cold months, usually mid-winter or in the spring. I used a product called "Klima cleaner pro" and sprayed it with the nozzle down into the defrost vents from the upper dash - it has helped a bit but the root cause is still there which means it will come back. It smells like Ammonia, which is what the bacteria/mold produce in the condensate water. There is a serious design flaw in these cooling system and I've brought my vehicle to be serviced 3 times they are still not able to fix it - they keep saying to change the cabin filter which was changed each time, and which doesn't resolve the issue at all.

I've read through the threads in this forum and the sIerra forum, but where the schematic says the drain should be is a flat spot on the firewall on my car. I notice that the condensate drips down on the transmission (driver side actually) and then down on the balancing tube on the exhaust mid-section where you hear it sizzling. I'm guessing this means the drain is actually above the transmission housing. I pulled the center console sides off and lifted the carpets up on both sides... no luck finding where the condensate drain would pass through on the transmission tunnel. If someone has a photo or screenshot from the service manual for the 2023 yukon showing where it is under the car - that would be great. I can find the rear one easily under the rear passenger quarter. Newdude's pic showing where it should be on the passenger side firewall: actual photo from the firewall:

It's honestly not even there any more in the 2023+ Yukon, the spot in the diagram that shows the drain is smooth on this firewall. Does anyone have updated schematics for where the condensate drain is now? Tore apart the lower part of the dash on both driver and passenger side, zero drain lines visible from the heater core or blower on the transmission hump or firewall. I sprayed a bunch of AC evaporator cleaner in the top vents and it seems to be draining out somewhere above the transmission on the driver side.