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

Classic Car Weekly (UK) - - Living With Classics - FUZZ TOWN­SHEND CCW’S MAS­TER ME­CHANIC

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’

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