The MGA heater system is the Smiths F275 unit, a 2¼ kW water-fed heater with integral blower fan, mounted on the horizontal shelf behind the engine. This node covers the internal heater components, the matrix (heat exchanger), blower motor, identification and caution plates, demist tube, seals, clamps and fastenings, for service or restoration of the factory heater. Water hoses, the water valve and the facia control cables are stocked under the Heater Hoses, Valve & Controls node; external ducting and demister vents under the Vents & Ducts node.
Smiths heater matrix, SHF7815-08
The heater matrix is the heart of the system: a tinned-steel heat exchanger carrying engine coolant through fine tubes with airflow fins, warming the air drawn through by the blower fan before it reaches the footwell and windscreen. The MGOC-stocked matrix is the Smiths SHF7815-08 standard-output specification, the original factory fitment for MGA pushrod and Twin Cam heaters (the complete heater unit numbers differ, FHR2453/01 pushrod, FHR2457/01 Twin Cam, but the internal matrix is the same).
The original Smiths matrix is a known weak point on any car of this vintage. The tinned-steel heat exchanger rusts from the inside over decades and can develop pinhole leaks or complete tube failures. Restoration-quality rebuilds are difficult, the tinned-steel construction does not lend itself well to re-coring, so when the matrix has failed, replacement is generally the most practical route. The SHF7815-08 is stocked as a direct service replacement to original Smiths specification.
Heater blower motor, Smiths FHQ6202-001
The Smiths FHQ6202-001 blower motor powers the heater fan. It is supplied without fan, the original impeller and its retaining clip are transferred from the old motor during installation.
This is a single-speed motor: the fan is operated by pulling the centre slide knob (marked "B") on the facia control panel, which closes the motor's earth circuit; the blower either runs or it doesn't, with no factory speed control.
Smiths identification and caution plates
Two plates are stocked for restoration authenticity. The Smiths heater identification plate is the small metal plate fitted to the heater body carrying the heater unit number (FHR2453/01 on pushrod cars, FHR2457/01 on Twin Cam) and the "F275" model marker. On a factory-correct restoration this plate should be present, legible, and correctly numbered for the car's variant. The caution plate is a separate warning plate advising on correct heater operation, also fitted to the heater body.
Both plates are often damaged or missing on cars that have had the heater stripped for cleaning or refurbishment.
Matrix inlet/outlet seals
Rubber seals for the heater matrix inlet and outlet pipes are stocked as service items. These seal the junction between the matrix water pipes and the heater casing, preventing internal air leakage (which would bypass the matrix and reduce heat output) and ensuring the matrix is properly supported within the casing.
The original rubber seals typically perish with heat and age; replacement during any heater overhaul is worthwhile.
Demist tube, MGA specific
The MGA-specific demist tube is the flexible duct carrying warm air from the heater to the two chrome-plated demister vents on the scuttle top above the facia. The tube length, routing and end fittings are MGA-specific, unlike the matrix and motor which are shared with other Smiths-heater-equipped classics.
Control cable clamps
Two cable outer clamps are stocked for the heater's control cables, one for the fresh air control (the right-hand knob on the facia, marked "Pull to increase" for heater output / "Demist" below) and one for general control cable outer-clamping applications. These clamps secure the outer sheath of the bowden control cables at the heater-end fitting, allowing the inner cable to move freely while the outer remains fixed. Cable clamps are frequently lost or damaged during heater disassembly.
Mounting hardware
Complete fixing hardware is stocked for heater assembly: 10-32 UNF × ½" screws with matching locking spring washers (No. 10) and plain washers (3/16"); No. 8 × ½" self-tapping pan-head screws for sheet-metal fastenings; and No. 10 (32 TPI) UNF zinc-plated nuts.
Ordering considerations
The heater matrix and blower motor are the two major service items on this page, both are common causes of heater failure and both should be addressed during any significant heater overhaul. The identification plate, caution plate and demist tube are restoration-authenticity items.