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Fresh water on the floorboards?

Oct 2, 2015 | Automotive

By Tom Torbjornsen

Dear Tom,
I own a 2000 Toyota Camry and the floor mat on the driver’s side is wet. It’s not coolant (it appears to be clean water) and the heater core is not leaking. The water is coming in even when it is dry outside. What could be wrong?
Sal from Brooklyn, N.Y.

Sal,
It sounds like the air conditioning (A/C) condensation drain is clogged with organic debris. This is a common occurrence and is easily remedied by simply cleaning the drain hose.
Tom

So how does this A/C water find its way into your vehicle’s cabin and onto the passenger’s side floor? And how does one clean the drain hose. Good questions. Let’s take a look.

Fresh water on floorboards? Where does it come from?
The air conditioner in your car not only cools the interior, but it also dehumidifies the air. Moisture is pulled from the vehicle’s cabin and collected in a drain within the A/C system. When you run the air conditioner, you can see this water draining onto the ground from under your car.

If A/C water is supposed to drain outside the car, then how does it end up inside?
The air intake for the HVAC (Heating Ventilation & Air Conditioning) system is located at the base of the windshield. When organic debris (leaves and other organic materials) gets sucked into the HVAC air intake, it finds its way into the lower parts of the HVAC box where conditions are warm and moist, a perfect environment for decomposition. This rotten organic debris forms an unholy, black paste. When this paste mixes with the water produced by dehumidifying the cabin’s air, it plugs the A/C condensation drain. Thus, the water has nowhere to go except into the vehicle and onto the floor.

How do you fix this problem?
Simply clean the condensation drain hose. This hose is usually located at the lowest point of the bottom of the HVAC box inside the vehicle (up front). It is usually a small black rubber hose that exits the bottom of the case, bends 90 degrees, and exits the vehicle via a hole in the firewall. This hole is usually lined with a protective rubber grommet to protect the hose. To unplug the drain, simply remove the hose (be prepared for the rush of cold A/C condensation by placing a small bowl beneath the spout) and clean it of the organic debris. Sometimes you have to work a small flexible wire up into the drain spout on the box because it is severely clogged. If you have to use a wire, be careful! The evaporator core is just above the drain spout and a sharp probe can damage it.

What if the problem keeps re-occurring?
In this case, there’s a blockage inside the box that will have to be removed by disassembling the HVAC box. Be prepared to spend a small fortune. Ah, the joys of car ownership.

‘Til next time … keep rollin’.

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