Heating
The UK doesn't exactly experience Arctic conditions, with the harshest winters being described as "a bit chilly". But numb fingers do detract from the pleasures of driving an E30, which is why your car is fitting with a Heating system.
The heating system is directly integrated into both the Cooling system and the Aircon system, if fitted.
Contents
Overview
The heating system provides warmth for the cabin based on engine temperature. By taking a direct feed from the engine coolant, a secondary radiator known as the heater matrix is warmed to very high temperatures. A fan then blows air over the radiator, creating a hot draught which is channelled into a number of vents around the cabin.
The driver directly operates the heating system through the controls in the centre of the dashboard.
Components
Controls
The control panel is a complex panel of dials and levers, the combination of which gives you full control of the Heating system.
The panel features two rotary knobs. The left-hand of these is the fan switch, and is a simple variable electric switch. It sends a signal to the heater blower to spin at the required speed. The right-hand knob is a potentiometer, and controls the heater valve. If the switch is within 20 degrees of its coldest setting, power to the heater valve is cut off, preventing coolant from reaching the heater matrix.
On 1987 and earlier cars with air conditioning (A/C) , the lever that regulates air flow for the instrument-panel vents also electrically controls the A/C compressor. To prevent condenser freeze-up and A?C system damage, the compressor is switched off if the lever is set below a certain point.
The flaps for air recirculation are opened and closed by small electric motors. The motors are connected to the flaps by adjustable rods. The motors are activated by a relay mounted on the heater box, just behind the control panel.
In between the dials are three levers. By moving these levers the driver can set the position of three cable-operated flaps within the vents, which will direct airflow around the cabin. The three levers allow air flow to the windscreen, the dashboard vents and the footwell vents respectively.
Heater Matrix
The heater matrix is essentially a radiator. Fed by two pipes from the cooling system, it sits inside the cabin behind the central section of the dashboard. The amount of coolant flowing into is regulated by an electrically-controlled valve, operated from the controls.
The core itself is contained within a large plastic shell, to incorporate all of the vent outputs, the controlling flaps and a water drain, if needed.
Heater Valve
Coolant flow to the heater matrix is controlled by an electric valve on the left hand side of the heater assembly. This electric valve is closed with the heat control fully anticlockwise, and is supposed to open when the control is just off its stop.
This valve will fail closed if someone has connected the two heater hoses on the bulkhead the wrong way around. When this happens, it often gets stuck closed. Because of this, many people mistakenly believe they have to replace the entire matrix, when only the valve needs replacing.
Heater Blower
In order to move the air around the cabin you need a form of fan, which in the E30 is called the Heater Blower. Rather than a bladed fan like an aeroplane's propeller, the heater blower looks like an old paddle steamer with two bladed wheels. These are driven by a centrally-mounted motor, and then the whole assembly is mounted on to the top of the heater matrix.
As a unit, it's accessible from the engine bay, where it sits just behind the bulkhead covered by a panel in the scuttle. There is no need to dismantle the interior of the car to access it.
A variety of blowers were fitted during the lifetime of the E30. Facelift motors (1987 onwards) are different from pre-facelift, and aircon motors are different from facelift. However, facelift aircon fans are very similar to the pre facelift version, and are possibly identical. This is very important when sourcing a replacement, since there is no chance of fitting a pre facelift motor and fan to a non aircon facelift heater box.
Vents
Air flow around the cabin was distributed by plastic pipes, concealed behind the dashboard and under the carpet. These pipes could channel air to the front footwells, rear footwells, front door windows and the centre of the dashboard. Airflow to the vents is controlled by cable-driven flaps, operated by the controls.
Common Problems
Leaking Heater Valve
This is the cause of 99% of "wet passenger footwell" issues. The heater valve connects the matrix to the stub pipes, and its joints and O-rings can break down over time. It's a simple if fiddly fix, made a lot easier by removing the glove-box.
The heater valve can also break if an incorrect radiator cap was fitted. Most were changed in a BMW recall, but it's always worth checking otherwise your valve could blow again in the near future.
Erratic Blower
Sometimes it only blows on full speed, sometimes it never works, other times everything seems fine. This odd behaviour of the blower motor is unsurprising after 20 years of no lubrication on plain bush bearings, but hopefully it's nothing a bit of TLC won't fix.
The motor does need to be taken out of the car though. Once on the floor, it can be freed up with WD40, powered up in your hand, then lubricated with a light oil - repeated again and again, until it runs completely free. Then re-install it. If this doesn't get it working, you'll have to source a replacement.
Blowing Only On Max
The fan itself can be a finicky little unit, and will either not work at all or, more commonly, only work on the MAX setting. If that's what's happening, learn more about heater fan problems.
Broken Stub Pipes
The stub pipes are the plastic tubes that connect the coolant hoses to the heater matrix. During engine work, especially engine swaps, it only takes a clumsy knock to break either or both of these pipes. It's a common E30 job to replace the bottom one , since it's part of the electric heater valve.
Either of the stub pipes is easy enough to replace; they are only held on with two small nuts and bolts and an O ring, plus a difficult-to-get-at self tapping screw if it's the lower one.
Take care to reconnect the heater hoses the correct way around after replacing the pipe.
Troubleshooting
If you're having more complex issues with your heating system, such as total failure, learn more about troubleshooting the heating system
