Club 80-90 Forums

Ive just taken my heater box apart to change the matrix. When I split the box apart I took out the matrix and the steel plate behind it cos it was coated in crud. 2 plastic flaps fell out from inside the heater box behind the steel plate and I cant figure out how they go back in again. Anyone familiar with the insides of the heater box and where these flaps go?

I had the same issue, 'fortunately' one was still half in so I could see where it came from. The other one was as you describe, down by the matrix (blocking air flow). I don't know what they're for, my only guess is that maybe they flap open one way when normal driving causes the natural draft to pass through the matrix and direct it where you want, then there's the van stopped scenario - put the fan on and as the flap is in the vertical orientation anyway, the fan being on will help 'close' the flap which will stop the air your fan is pumping out from going out the inlet vent and make sure it goes through the heater matrix and directed where you want it.

Hard to describe of course, and I didn't take a pic when I had it out last week, but may do in the spring when I have it all out again to do the windscreen corner... but here goes
With the fan motor out, you can put your hand down that hole and then the flaps fit up in either of the rectangular slots that are open facing you - with the pivot at the top - there should be two short round tabs on the flaps that slot/clip into some holes. Now mine did seem to clip in ok, I think it was outside tab first slotting into hole, then the one near the middle of the box fit into a clip. But after a bit of testing by poking it, it half fell out anyway so I thought rather than have it fall down and restrict the flow through the matrix, I'd do away with them for now and figure out a way of enlarging the tabs so they wouldn't fall out - but not by much, since they need to turn.

these things are never simple are they

I pretty much figured the same thing. There is a cover on the bottom of the heater held on by six screws which when removed gives good access to these flaps. The flaps seem to act as a non return valve when the fan is on by the air pressure in the heater box closing them.
The flaps are a push fit into an open socket joint which wears and they fall into the bottom of the heater box.