A: In most vehicles, the A/C drain line can be found under the passenger side of the vehicle, specifically between the cabin side of the firewall and the evaporator. If you look at where the water is dripping when you’re using the A/C on a humid day, you can get a good idea of where it is located. On some vehicles, the evaporator drain isn’t visible without removing heat shields.
The A/C drain line (or drain pipe) allows condensation to escape. Water condenses on the evaporator (the heat exchanger in the dash) like it does on a cold drink can and must be allowed to drain out of the evaporator housing. If the drain is clogged, water will accumulate in the evaporator housing and will eventually spill out on the carpet inside the vehicle.
A foul odor coming from the A/C vents, sloshing noises behind the dashboard, and a damp floorboard are common indicators of a clogged drain line.
Before unclogging the drain line, make sure that the engine is shut off. Hoist your vehicle using a hydraulic lift for easier access.
You can choose from several A/C drain cleaners on the market. You’ll usually need about 1/3 of the product for a thorough cleaning.
Keep in mind, however, that certain drain cleaners can be harmful to your vehicle. Always consult your owner’s manual before conducting any cleaning or repair tasks.
When spraying the cleaner inside the pipe, make sure to let it soak for a few minutes before draining. You might also want to roll down the windows to let the fumes out.
It’s also important to clean other parts of the air conditioning system, such as the vents and filters, for proper A/C operation. In some cases, the evaporator coil might also need to be replaced. Doing so can cost anywhere between $400 and $950.
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