S3 E-Type

The Heater Matrix
Some views inside that fangled heater box.

by Dave Lacey

Some rather ugly pics here of what i found inside the heater. Gives a basic idea about how it's meant to work.

This component is so rusty I question if it's original on this car: as you'll see the bottom of the unit is almost rusted out...whereas the rest of the car is rust-free ???!??
Here it is [upside down] as removed.

The fan is a normal centrifugal type:

The construction of the box surrounding the heater matrix itself is like someone's school project rather than the work of of luxury/performance car professionals... It's multiple ~flat plates screwed together:

The flap operates in a simple 2-position "digital" mode; either blocking the heater matrix in the upright position [and allowing the air from the blower to be "vented"], or in the flat position blocking the vent and forcing the air thru the matrix. If the sealing in this 2nd position is not good then i guess most of the blowers air is "wasted". The seal is accomplished by a layer of foam on the flap, after 20++ years all the foam has disintegrated....

Control of temperature is via control of the hot water valve feeding the matrix, here you can see the valve and the sensing coil mounted "downstream" of the matrix:

There is foam around the matrix to seal it against the casing so that air goes thru rather than round the matrix.The foam seems to be one cause of the corrosion; it has obviously trapped water underneath the matrix causing extensive corrosion:

Here you can see the vent (a plastic moulding) and the foam on the back of the flap that should seal against the vent:

The empty casing shows the extent of the rust, on cleaning this up further a number of holes appeared....

I just wanted to show you what i found so that you might understand how it works and how it can influence the heating in the car. To me its a little unusual in that the water supply is thermostatically controlled and the air supply is just on-off. This means the controls in the car arent "variable"; they just determine if the heater is on or off. If the air blowing is feeble, it could be the fan or the sealing of that flap to the plastic vent. If it's always cold then the thermostat could be faulty...
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