Can I put a tap in my heater line?

Yes, you can. My County has had a tap in the line since before I purchased it over 100,000km ago.

Yes. You can install a valve. No issues.

Great, thanks gents, fitting the electric tap will be a lot easier than finding and replacing the original cable system.
Cheers,
Paul

Fix the cable as well. It is $10 and 30 minutes of work. Very easy job.

I think my Mortar Carrier has been upside down in a muddy swamp.... or something similar. The cable operating mechanism is seized solid with mud and rust, and someone has tried to un-seize it by force and bent things.

Also the electrics were a nightmare - lots of very un-professional fixes, such as wires poked into sockets and held there with masking tape, and lots of burned wires.... with the huge tangle of wires under the dash repairs were really not viable. So I have ripped all the electrics out and will start again making things a lot more accessible for the future. Having a little extra dash space by deleting the heater controls helps.

My lesson... it is not always a good idea to buy vehicles sight-unseen! But thankfully it does drive very well - well worth the effort to fix properly.