One other thing. It's best to wait until the engine has some heat in it BEFORE turning on the heater blower. After all, the heater matrix is just another radiator. Thanks Mike, you've given me some ideas for my other project.

Got my bulkhead done on petrol 110 after sealing up heater matrix and heating box now have a drivers side heater new fan and resister all good

Just love your very British approach, very entertaining and thought provoking 👍 I need to put new foam in my seats, ant was thinking of fitting sear heating elements in at the same time. But my 300 TDI pick-up's heater is a massive improvement on my 1974 Series 3 🙂

I put a Defender heater into my 109 hard top. It isn’t modified, just stripped and cleaned out, and the same for the dash. It heats the interior really well and within five minutes at -5oC was too hot to keep on the high flow, just like yours. Even when we had that week-long -17 snap in 2012 or so, it only needed a few minutes to warm the whole 109 interior and occasional boost on the high fan speed for a minute or two. The trick is to make sure the matrix and its pipes and hoses are clean of rust and scale and that you don’t have air leaks from the heater casing or the lower dash trunking, and make sure that the baffle plate that blocks the cold air route inside the housing is adjusted correctly. Setting the vent control flap adjustment and making sure the flaps themselves have a decent seal pad on them to close against the inside of the dash trunking makes the demisters much better too. The standard system is pretty capable if in good condition, its biggest problem being the Tdis cooling down too much to provide hot fluid to the matrix if idling while parked for significant times.

The V8 gets hot quickly so even with the heater off (cold) it seems to get boiling inside. If and when I get it back on the road, the keep fit air con will be in operation in the summer months. Great idea with the re-circulation.

I wound up putting the blower on a rheostat for more range of control. I like the recirculation idea. Thank you for the project!

I've got them Chinese diesel heaters, good for defrosting and warming up the interior without having to go outside ( got upgraded remotes with display ) but they don't warm up the engine coolant ( yet ) and in the full tilt series 2 it's brilliant because the Smiths heater it's got is useless.

Great idea but because you are sucking the inside you are also drawing in dust and fumes through any holes or gapes in the body, where sucking outside pressures the cabin stopping dust and fumes. 😮

Spot on young man, your talent is needed in the uk, rust buckets a plenty to work on 🙊

Think I need to replace my blower unit (sometime) it never blew that well and now doesn’t seem to blow at all. Not sure any owner can worry about reintroducing condensation by recirculating the air, the gaps around the vehicles allow enough fresh air in 😂

Note; we use the air con to omit condensation from the windshield in Australia, it works really fast although a little uncomfortable in winter for a short time.

That’s quite a bit of engineering and fabrication you’ve done that’s an excellent layout. Very ingenious. No, the recirculated air wouldn’t fog up because the outside cold air cannot hold as much moisture as warm air and when that cold air warms up, it becomes much drier.

Must you...? My heater is another damn thing to do. However, the start I made was using old computer Mouse Mats cutout as the bulkhead heater gasket' - and while I was in about there - used a whole one as an 'anti-vibration plate between the arse of the heater box and where it sits against the rest of the bulkhead too. I used them in a couple of other places as well... Got a good few old Mouse mats lying about (I'm an ex- I.T wonk ) and because they are closed cell foam/hard plastic - they're cheap and ideal for... well anything really - up to and including soundproofing. Hardwearing, easy wipe clean, can be rivetted, self-tapped, or glued. What's rattling in the Landy?

I have the opposite issue living in Australia whereby the warm air leaks into the cab even though the selector arm is on cool with fan speed off. I have had to isolate the coolant water flow from the heater box during the summer months using an old 70`s Holden car valve. The LR Defender air conditioner is less than adequate without having to also work against warm air from the heater box. Note the upside with the TD5 is its a very overcooled engine set up which suits our climate.

Oh no, you've planted a seed in my head, think I will try and control my blower with a room thermostat ha ha.

Goodness gracious you.

I wonder if it’s possible to add a recirc flap to a stanadard heater. I’d like to keep the fresh airflow but add even partial re circulation pipe controlled by a valve, flap or maybe even a separate fan, just an idea?

Now, if you were to wrap those long lengths of copper pipe in the engine bay with that plumbing pipe foam tube stuff, you'll lose less heat before the coolant gets to your heater matrix. Imagine that, you'll then be able to roast a chicken in the cab and have a hot chicken lunch while you're out on the road🤣👍