The Car Doctor: Make sure you set your seat safely to avoid airbag injury

What is the minimum safe distance from a driver airbag?

IH, Wolverhampton

According to the National Highway Traffic Safety Administration, placing yourself 10in from your air bag, measured from the centre of the steering wheel to your breastbone, provides a clear margin of safety.

To change driving position, move your seat to the rear while still reaching the pedals comfortably. Slightly recline the seat. If this makes it hard to see, raise the height, or use a firm, non-slippery cushion. If your steering wheel is adjustable, tilt it downward. This points the air bag to your chest instead of your head and neck.

I've got an liquefied petroleum gas (LPG) converted Rover 25 which idles erratically. Why?

PB, Shepperton

Conversion should be carried out in accordance with the LP Gas Association's code of practice. The bad idle could be due to a number of problems. Petrol is used to start the engine through electronic injectors and they may not be shutting off,.

The computer chip controlling the system may need to be reprogrammed, so go back to the convertor.

The light in the boot of my 2001 Jaguar XJ8 keeps falling out.

RS, Sittingbourne

If your XJ8 is still under warranty get it sorted out at the next service. However, if the light is mounted in the carpet, that may be shrinking and loosening the light fitting.

Blu Tac is a quick fix, or some electrical tape will provide a snugger fit.

The heater in my 1990 BMW 316 only blows cold air. Why is this?

DT, Preston

It could be a failure of the heater matrix, or a leaking head gasket which directly affects the cooling system.

Replacing the head gasket is the more costly option, as the top of the engine will have to be dismantled.