Front and rear foorboards wet after running AC.

[SharpRedOne]

2009 Buick Lucerne CXL
Any idea as to why the floorboards will accumulate water after running the AC. It seems to be wet from the under seat vents in the rear and can't really tell where its coming from in front.
It did this last year and I had to put oil dry in the floor to absorb the water then vacuum it out. Thought it was because of restricted air flow from stuff in the floor but nothing like that now.

 

[Mad_Coachman]

Drain tube is clogged. I'm sure a Lucerne guru will be along any moment to elaborate but I'm imagining it would be somewhere near your front passenger area. Get down and take a look with a mirror. They sometimes get clogged with debris and your evaporator can't get rid of the excess moisture so it sweats onto your carpet.

 

[2007LucerneCXL]

Here's the diagrams on the drains, but most issues are with the passenger side floor getting wet, if only the rear it may be something else See post # 7.

'06 Lucerne CXS Water on the passenger side floorboard.

After doing a few hours or research, I pulled back the passenger side carpet to find a puddle of water underneath. Ir was enough to soak two large bath towels - the ones you dry off with. Research says I'm looking for a leaking hose somewhere back behind where the top of the carpet goes back and...

buickforums.com

When saying it's in the rear floor do you have a sunroof? Is the trunk dry and have checked the spare tire well? Is there any wetness under the back seat area? These are some other things to check in case it's not AC related. There was another Lucerne on the forum which had a leak, but he had purchased it used and come to find out it had a poor repair in the rear quarters and wasn't sealed in the wheel well properly.

 

[SharpRedOne]

Here's the diagrams on the drains, but most issues are with the passenger side floor getting wet, if only the rear it may be something else See post # 7.

'06 Lucerne CXS Water on the passenger side floorboard.

After doing a few hours or research, I pulled back the passenger side carpet to find a puddle of water underneath. Ir was enough to soak two large bath towels - the ones you dry off with. Research says I'm looking for a leaking hose somewhere back behind where the top of the carpet goes back and...

buickforums.com

When saying it's in the rear floor do you have a sunroof? Is the trunk dry and have checked the spare tire well? Is there any wetness under the back seat area? These are some other things to check in case it's not AC related. There was another Lucerne on the forum which had a leak, but he had purchased it used and come to find out it had a poor repair in the rear quarters and wasn't sealed in the wheel well properly.

No wetness anywhere else but floorboards. No sunroof. Under rear seat and spare tire well dry. I bought this used a couple years ago and it had a clean Carfax on it with no accidents. I'm going to jack it up and check for plugged drains today.

 

[2007LucerneCXL]

The panel seams might also be something else to inspect. Not saying that the AC couldn't cause a problem getting the carpet wet but it's somewhat a long distance to the back seat without getting other floorboards wet in front also.

 

[SharpRedOne]

Drain tube is clogged. I'm sure a Lucerne guru will be along any moment to elaborate but I'm imagining it would be somewhere near your front passenger area. Get down and take a look with a mirror. They sometimes get clogged with debris and your evaporator can't get rid of the excess moisture so it sweats onto your carpet.

That was my first thought. I'm jacking it up today and going to check drains.

The panel seams might also be something else to inspect. Not saying that the AC couldn't cause a problem getting the carpet wet but it's somewhat a long distance to the back seat without getting other floorboards wet in front also.

Front floorboards were wet as well just not as much.

I did find the AC drain tube and it was clogged closed. Opened it up and drained about a quart of water out of it.
Also the drain tube is near the exhaust manifold and has gotten hard and brittle with age and the lower portion has fallen off leaving a short straight drain. Going to order a new drain tube.

THANKS ALL FOR YOUR SUGGESTIONS.

 

[Mad_Coachman]

Glad you kept it simple.

 

[2007LucerneCXL]

Happy you found it. If more water got to the back then the front you may want to check the under the seat control modules.

 

[SharpRedOne]

Happy you found it. If more water got to the back then the front you may want to check the under the seat control modules.

This model has air vents under the front seats for the back, so I'm assuming the water came through them. Seats are working as they should. It's been outside in 90°+ sun for 2 days to dry out the moisture.

 

[2007LucerneCXL]

Depending upon what was installed with options they also ran under the seat. But as long as it's getting air through it and can dry out it should be good.

 

[HotZ28]

Water does not flow through the vents, unless it was sucked up and went through the fan! If that were the case, the fan motor would fail sooner than later. If the EVAP drain plug was blocked and leaking into the front carpet for an extended period of time, it will travel & go backwards to the rear carpets/floor during car acceleration.

 

[SharpRedOne]

Water does not flow through the vents, unless it was sucked up and went through the fan! If that were the case, the fan motor would fail sooner than later. If the EVAP drain plug was blocked and leaking into the front carpet for an extended period of time, it will travel & go backwards to the rear carpets/floor during car acceleration.

It was not wet under the seats, but from the vent outlet for the back seat into the rear floorboards. Might have been sloshed into vent tube during acceleration as you said and moved by the air flow. Fan motor works fine.