MG Tech – Uprating an MGB Heater System

Roger Taylor offers some advice on how to upgrade the heating system on an MGB with a modern replacement system that will not only be warmer but also more efficient.

The first thing to do is to remove the screws and disconnect the heater box under the bonnet just in front of the bulkhead. You will also need to disconnect the heater hoses and the operating cable which is linked to the dashboard mounted switch.

This latter operation is not an easy task and may need more than one pair of hands.

Once you have the box out remove the front cover which will expose the heater matrix, a sort of mini radiator, and an electrically operated blower.

Remove the old heater matrix and in its place you can fit an uprated unit which has a larger water capacity although it has been designed to still fit in the same space as the original matrix.

It is also possible to fit an uprated two-speed heater fan (older models only came with a single speed fan) which has a larger impeller to produce a higher flow of air into the cabin. Again this has been designed to slot neatly back in place of the original unit.

If you are replacing the older single speed motor with a two-speed blower you will also need to fit a two-speed switch.

Finally it is advisable to fit new air seals when you are re-assembling the air box. It is also possible to fit new foam bands in the radiator box to reduce vibration.

Installing an uprated matrix not only offers more warmth for occupants but will also help to cool the engine as more warm water is circulating through it, dissipating the heat.

Such a replacement operation will take the best part of a day if you are confident about what you are doing – alternatively get an expert to do it for you and they will take between three and four hours. They will also be able to check the water flow in the matrix to make sure it is working efficiently.

A replacement uprated heater matrix costs around £65 (a standard matrix is £45) and a two speed fan will cost £65 (a replacement single-speed fan is £40). The foam padding and seals will add another £10.