SEO Description: MGA Heater Plumbing and Controls, Heater Water Valve (MGA+MGB Pattern and MGA Heater Inlet Valve), Heater Hoses, Copper Heater-to-Pump Pipe, Water Union, Supergrip Hose Clips, Facia Control Panel Bezel, Blower 'B' Knob, Air Distribution Knob, Control Cables & Trunnions | MGOC Spares Body copy: This node covers the water plumbing between the engine and the heater matrix, the heater water valve, and the facia control cables, knobs and panel hardware that operate the heater from the driver's seat.
Heater water valve, two options
The heater water valve is the on/off tap in the hot water line, when the heater is not needed, the valve closes and stops hot coolant circulating through the matrix, keeping the cabin cool. When heat is wanted, the valve opens and allows engine coolant through the matrix. The valve is operated by a cable from the facia control knob. Two valve options are stocked.
The heater inlet control valve is the service replacement for the valve that mounts at the water inlet of the heater matrix. The A+B pattern heater valve is a common-fitment valve that suits both MGA and MGB applications, useful because the MGA and MGB heater water valves share the same mechanical specification. A heater valve gasket is stocked as a service item for resealing the valve at its mounting flange during any valve replacement. At chassis 61160 (January 1959), the factory introduced an improved heater water valve design; earlier cars had a less reliable valve that was superseded.
For pre-61160 cars, either the original-pattern valve or the later improved specification can be fitted, with the later design being the more robust choice.
Heater hoses and water plumbing
The water plumbing between the engine and the heater matrix consists of rubber hoses connecting to a short length of copper pipe on the engine side. HOSE HEATER MGA is the MGA-specific heater hose, stocked in two positions (flow and return). The MGA hose specifications are specific to the car, the hose lengths and bends are not shared with the MGB. HOSE WATER RETURN is the return-side heater hose.
COPPER PIPE HEATER-PUMP is the pre-formed MGA copper pipe connecting the water pump to the heater return feed. WATER UNION is the union fitting for joining hose to water pump or heater return junction. Supergrip twin-wire-loop hose clips (9/16", 3/4" range) are stocked for securing rubber heater hoses. These are a period-correct style of double-wire hose clip (different from modern jubilee-type worm-drive clips), giving a neater and more appropriate appearance for classic MG engine bays.
For a concours-judged car, the twin-wire clips are the appropriate choice.
Facia control panel, bezel, knobs and fixings
The heater controls are on a small black add-on panel below the centre of the main facia. MGOC stocks the complete set of facia-panel hardware. The Bezel, 'Panel', Heater Control, Printed is the decorative/identifying bezel fitted around the heater control panel, with printed control markings. The Bolt & spacer kit, heater control panel fixing comprises the fixings that secure the add-on panel to the main facia.
The Switch, heater control, with levers and wires is the electrical switch behind the control panel, actuated by the blower knob, supplied without knob (the knob is a separate item). The Knob, heater blower control, 'B' is the centre slide knob, factory-marked "B", which is pulled out to activate the blower fan. The Knob, air distribution control (no ID letter) is the left-hand knob on the facia panel, unlabelled on the knob itself (the markings "Push" above and "Air" below the knob are printed on the bezel). Between the three knob/switch items and the bezel plus fixings kit, the entire facia control panel can be rebuilt to factory-correct appearance.
Control cables and trunnions
Two cable specifications are stocked. CABLE HEATER MGA is the standard-length heater control cable. CABLE HEATER LONG A/A is a longer heater control cable for installations requiring additional cable routing length; confirm fitment before ordering. Trunnion, Nipple, With Screw, Control Cable End (Hex Ended Trunnion) is the cable-end fitting with integral nipple and grub screw, used where the inner cable terminates at the valve or blower-switch lever.
The trunnion provides the fixing point between the inner cable and the operated lever; the grub screw clamps the inner cable in place. Service items that are frequently lost or stripped during heater disassembly.
Ordering considerations
For full heater plumbing replacement during restoration, the relevant hose set, the copper pipe, water union, hose clips, heater valve (with gasket) and control cables will all be needed.