This is the heater matrix from our 1992 Eunos Roadster, which is being converted into our MX-5e. The matrix has a small radiator that sits within it and is part of the engine cooling system. A complex set of internal flaps enable cooled air (from the air conditioning unit) to be passed through and heated if rerquired. This unit also controls where the air is directed to.
The heater matrix is in two main parts, held together with 7 metal clips.
Many of the internal flaps are covered with a soft foam, which crumbles to dust over the years. This foam serves as a seal and also as a damper, to reduce the noise of the flaps when sealing against the plastic.
The whole flap doesn't need to be covered in foam though. It works just as well with foam tape around the edges and on any other contact points.
The flaps are mostly held in place with plastic clips and can be easily removed. We have removed each one and cleaned the old foam off with a wire brush. We have no idea what they are made of but we then cleaned them with brake cleaner and then painted them using a primer first.
Once painted, we have a smooth and clean surface to attached some stick foam tape. We painted them this colour simply to use up some old cans of spray paint. This was the colour of Yoko when we bought her back in 2016.
The foam tape is simply stuck along the flap edges, where it is required to make a seal.
The first half of the heater matrix has two flaps.
The second half of the heater matrix is more complex with 4 flaps.
It's always a good idea to take lots of photos before you start dismantling something like this.
The second half completed.