Morris Minor Owners Club

Does anybody know if it is possible to replace the rheostat on a round heater without removing the heater unit, i'm handicaped so i might find it hard to scramble around under the dash for too long.

I think it would be quicker and easier to remove the heater first than to try and remove the rheostat in situ, even if it were possible. A certain amount of dismantling is required.

There are different Round Heaters, the factory fit Smiths Round Heater was just one model. Many cars left the factory heater-less and had aftermarket ones fitted.

The one similarity is they all require the front to be detached so also unfastening from the vehicle body.

I'm afraid only you, with your own knowledge of your capabilities, can decide if you can do it; whether easier to try in-situ or remove.

This is the illustration of the Morris factory fit one, I've highlighted the fixing and the case retaining clips.
I've seen some photos where there are 3 clips, some have 4.

The illustration shown above is for the earlier factory installed heater. Removing the front panel will require supporting the heater and perhaps dropping the front of the parcel shelf. Sometime in 59 the installation is more complicated. The heater is surrounded with metal ducting which needs to be removed in order to get to the retaining clips and then the parcel shelf was made deeper with a cover over the heater. The vintage of your Minor changes the complexity for removal.