How stuff works: Fuzz Townshend demystifies the heater matrix
EVERYTHING YOU NEED TO KNOW Our man Fuzz cuts through the fog and hot air to demystify classic demisters
There was a time within living memory when in-built heating and demister systems were an expensive optional extra on most cars. As a boy, I myself had what was commonly known as a ‘car coat’ – a long, heavy garment designed to keep its occupant just above freezing point when travelling in frugal, low-specification vehicles.
As owners’ expectations rose, so cars began to be automatically specified with heating and ventilation systems more in-keeping with modern home comforts. This meant that heavy coats could be swapped for nylon bomber jackets and driving gloves could be banished from regular motorists’ sartorial accoutrements.
At first, the equipment was rather cumbersome and consisted of a circular self-contained radiator matrix enclosed in a sheet metal casing. This featured an electrically-driven fan and a couple of rudimentary flaps which, when closed, directed a puny waft of warm air via flexible concertina pipes up to a pair of tin, fish-tail diffusers placed below the windscreen. The resultant draught provided a means of clearing misted-up windscreens on cold mornings. With the flaps open, heat was circulated – rather weakly – out into the front footwells to do battle with cold air finding its way in through pedal apertures and the like. The only way of turning the heat on or off was via a tap, generally fitted on to the cylinder head.
Sophistication improved gradually, with the heater matrix and blowers hidden away behind the dashboard or buried in the engine bay, and remote cables operating flaps to direct the more powerfully puffed warm air to wherever it was required within the cabin.
Larger and more efficient heater matrices and multi-speed fans eventually led to genuinely warm air being distributed throughout the whole interior of the car, resulting in almost tropical interior heat, even when the outside temperature was low. All of this was further assisted by much improved body seals. The rapid clearing of misted windscreens was also a huge boon for road safety, meaning that the days of keeping an old rag handy, or the application of ‘magic fluid’ – a mixture of water, washing-up liquid and vinegar – were relegated to the past.
Some later classics featured ever more sophisticated heat management systems, with the use of multiple thermostatic switches to operate servo-actuated flaps, helping to avoid initial icy blasts and to maintain a comfortable cabin temperature. However, the core of the system remained the same – a coolant-fed matrix, similar in construction to the main cooling-system radiator, taking its supply directly from the cylinder head, where running temperature was quickly achieved. In short, car heating systems scavenge what would otherwise be a wasted byproduct – heat.
Heater matrices can also have a beneficial warning effect. If they suddenly blow cold when heat is expected, it is often because of low coolant levels, sometimes as the result of a faulty cylinder head gasket or cracked coolant jacket. If your car’s heater blows cold, check the temperature gauge immediately – you may well find it sitting in the red.
‘Cars began to be automatically specified with heating and ventilation systems more in-keeping with modern home comforts’