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Repairing a plastic auto mirror housing can often feel like an exercise in futility, despite the many products on the market that promise to do the job for you. Auto mirror housings are made from ABS plastic, which is rigid and resistant to adhesives. Even a fiberglass patch will not hold to the smooth plastic. But you can repair plastic auto mirror housing using a simple soldering technique and about 20 minutes of your time.
Step 1
Sand the edges of the crack where the auto mirror housing is damaged with 80-grit sandpaper. Remove any paint or finish on the plastic. If the plastic has a hole and not just a simple crack, sand all the edges surrounding the hole as well.
Step 2
Plug your soldering iron in and let it fully heat up. While it is doing this, lay plastic filler into the crack in the mirror housing or, for larger holes, duct tape a piece of fine metal window screen in the hole so the screen is attached on the inside of the housing. Then lay the plastic filler over the screen. If you are using broken bits of ABS plastic as your filler, lay the pieces in the crack or on the screen so they do not extend beyond the surface of the rest of the housing.
Step 3
Hold the tip of the soldering iron between the plastic filler and the plastic of the auto mirror housing until it melts and joins, working slowly. The plastic needs to melt completely and join---not just the surface, or it will form a cold weld that will easily break. Keep a rag handy to wipe the soldering tip clean as you move around the edges and melt them together.
When the plastic has cooled, cover the repair with Bondo, let dry and sand down to match the original surface of the mirror with a 250-grit sand paper. Paint the entire auto mirror housing (and repair) to match.
Tip
- Touch a bit of regular solder flux to the tip of the soldering gun before you begin to "tin" the gun. This will help the heat to spread evenly throughout the tip.
Warning
- Do not solder plastic in an enclosed area, the fumes from melting plastic are toxic, and proper ventilation is a must to avoid poisoning.
Items you will need
- 80-grit sandpaper
- Soldering iron (25 watts, large tip)
- Plastic filler (or extra pieces of broken ABS plastic)
- Fine metal window screen
- Duct tape
- Bondo
- 250-grit sandpaper
- Auto plastic paint
