PeachParts Mercedes-Benz Forum - View Single Post

Squiggle Dog · #85 06-21-2018, 06:07 AM

The foam on the early style defroster flaps are held on by adhesive and metal rivets, which isn't very nice. Fortunately, I have the later style ones that have retainers that snap on. Sometimes an evil Behr employee would plastic weld the ends of the snaps so the retainers couldn't be removed. Mine were like this, so I used a spare set. With care, the retainers can be pried off of the flaps.

I used 1/8" thick extra soft resilient high temperature silicone foam from McMaster-Carr for the defroster flaps. The stuff is very difficult to make small cuts in, so accuracy is key. I cut the foam larger than the flaps because it's necessary for them to actually seal. They are about 2mm larger at each side, and about 5mm larger at the front and back. Put basically, I cut a hollow rectangle of the proper size with rounded corners so it would fit onto each flap in one piece around the molding lines and then snapped the retainers on top, which have teeth that hold the foam in place.

I found that the ETR switch probe wire from the manual air conditioning dial switch won't reach up to the top of the case where the one from the automatic system is supposed to enter. So, I decided to drill a hole in the front cover for the copper tube from the manual cover to fit through, as was intended for the manual system. However, the inside of the automatic case is reversed compared to the manual case--just inside the front cover of the manual case, the area above the heater core is covered with plastic, and the copper tube goes over this and then goes down into the evaporator through the open area above it. Just inside the front cover of the automatic case, it's open above the heater core and closed off above the evaporator. So, I had to drill an oval-shaped hole in the covering above the evaporator for the copper tube to slide through. But, the angle was wrong, so I had to carefully bend it to shape--which is not easy because it's easy to kink and having the probe wire inside it while bending is a must! I eventually got it to fit and used tar-impregnated cork tape to seal up the gaps and insulate the tube.

In order to have slider controls, I had to use a lower flap housing from a manual system. But, in the manual systems, they have plastic covers welded over the flaps, also known as "blend doors". I have no idea how you would remove the blend doors with the plastic covers in place--maybe it can't be done, and it certainly seems they weren't designed to be removed, anyway. So, I cut off the covers for access to the blend doors. Once they were cut, I carefully pried on the side of the doors in an effort to lift them out. I was so afraid I was going to break the plastic. I used a heat gun to soften the plastic, but on the first one I got it a bit too hot and it deformed a little. Fortunately I was able to heat it up and bend it back.

Once I had one side lifted up, I was able to angle the door and then pop the other side out of socket.

On top is the lower flap housing from the automatic case. On bottom is a lower flap housing from a manual case after I cut off the covers above the blend doors and the center partition between them which would have interfered with the large version heater core. After cutting off the excess plastic with a Dremel tool and carefully filing them flat, I brushed some acetone on the cut edges, which made them smooth and shiny.