Numerous seals make your vehicle’s interior cabin watertight. The vapor barriers are some of these seals. Found in the doors of your car or truck, they contribute to your comfort when it’s raining. They also protect vulnerable parts of your vehicle from corrosion and damage. If you must replace the interior door panels, exert care when handling the vapor barriers.
What is a Vapor Door Barrier?
The vapor barrier is a protective sheet attached to the interior of the car door frame. It’s usually made of a clear plastic that lets you see through the material and view the inside of the door.
Other names for the vapor barrier are:
- Dust barrier
- Moisture barrier
- Water barrier
Most door bottoms have weep holes that rapidly drain the fluid out of the door. The water barrier keeps moisture and condensation from reaching the door panel and interior.
What Does the Vapor Barrier Do?
The primary job of the vapor barrier is to block water vapor. It keeps the interior of your vehicle dry, ensuring your comfort and protecting various parts that might develop issues if exposed to moisture.
Water Seal
In many trucks, the vapor barriers serve as the primary water seals of the door. While the door has weatherstrip seals that prevent moisture from entering the gaps, the beltlines might not completely stop the water flow. It’s up to the vapor barrier to stop the rest of the water from reaching vulnerable parts.
In other vehicles, the car door vapor barrier is the secondary water seal. It will stop water in case the primary seal fails.
Dust Seal
The vapor barrier protects against small particulate matter, such as dirt and dust. It keeps surfaces clean by blocking airborne particulate matter from settling on parts, such as the wires that connect electrical parts to the electrical system.
Debris Protection
Furthermore, the vapor barrier blocks larger particulate matter. These debris are big enough to cause dents and scratches when they hit something. The vapor barrier can sufficiently slow them down to prevent any damage.
Protects Wooden and Wood-Based Parts
Some vehicles have trim made of wood or a material based on wood. One popular material is particle board, an engineered product made from wood chips and a synthetic resin that binds the material together when heated and put under pressure.
Wood looks great and can usually take a beating, especially if coated in a protective layer, such as varnish. However, the material remains vulnerable to moisture. If condensation forms on the surface of the wood, it can cause the material to swell and rot. Particle boards tend to rot faster than conventional wood material in the presence of moisture.
Fortunately, the vapor barrier stops water vapor from condensing on the door panel, protecting nearby wood or wood-based trim from moisture.
What Happens If the Vapor Barrier Fails?
Vapor barriers generally last a long time. They’re not exposed to harsh conditions like gaskets and seals in the engine or transmission. However, they can still wear out earlier than the manufacturer designed them for.
Their plastic composition leaves vapor barriers vulnerable to extreme heat. If one of the wires in the door gets exposed wiring or other issues, it can burn and melt holes in the sheet.
If you drive with a damaged or missing vapor barrier, you leave various parts vulnerable to corrosion and damage. Take the power window motor connector as an example. The connector’s plug features some metal surfaces that can corrode or rust.
If dirt gets in the power window motor connector plug, it might interfere with the current flow to the power window motor. If moisture enters the connector, it can result in corrosion that also interferes with the power flow through the plug. Corroded or clogged power window motor connectors can cause various problems and trigger various diagnostic trouble codes.
Don’t ignore a damaged vapor barrier. If you remove the water barrier, immediately install a replacement. Furthermore, attach the new vapor barrier with the utmost care to avoid leaving gaps that vapor and particulate matter can enter through.
How to Replace a Car Door Vapor Barrier?
Installing a new vapor barrier doesn’t require much experience in automotive repair. You can even perform the job yourself.
Home-Made Vapor Barrier
While you can get a vapor barrier from a shop, you can also use a home-made barrier. Find a sheet of heavy plastic film that fits over the door frame. You want to seal the sheet’s borders against the frame to ensure moisture doesn’t get through the plastic.
Attaching the Vapor Barrier
Most door vapor barriers use butyl tape to attach them to the door frame. Indeed, many car manufacturers also use the same type of adhesive tape on their stock water barrier.
Older models might use tack strips to attach the vapor barrier. They pin the plastic sheet against the frame. Depending on the design, you might want to apply adhesive.
Alternatively, you can get a tube of silicone adhesive. Apply the glue to the surface of the door frame before attaching the vapor barrier. Cut out the excess parts of the plastic film.
What you shouldn’t use is duct tape or other conventional tape. They can dry out over time, losing their stickiness and forcing you to clean them before using a different adhesive.
Cut Openings in the Vapor Barrier For Wires
Mark the spots on the plastic sheet where you must cut slits or holes for the wires to exit the door. Cut the openings and draw the wires out through them.
Next, cut out patches from the excess plastic sheet. Place a patch over each opening to act as a waterproof cover. Apply butyl tape to the edges of the patch to seal the patch against moisture.
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