Anyone using the ministry defender heat/hvac kit

Yes. You can’t only recirculate air in the winter. The humidity will keep increasing until the windows fog up. It is just a plain fact of science. You need to bring in fresh air to keep it below the dew point at the window temperature.

I'll add that I don't have first hand knowledge of this HVAC system. But the fact that they designed it without a fresh air intake (which would be easy to add), shows me that the designers do not know what they are doing.

Z.G said:

The 300tdi just doesnt produce much heat in the colder months in the northeast

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This is not true. The engines produce enough heat. The stock matrix is not a bad size, but is not very efficient. This results in a high approach temperature (difference between coolant and heated air temp). A better matrix helps a fair amount in reducing the approach. I use a heater than has been measured to output 2.5 times the heat as the stock heater so it clearly is not an engine limitation.

Beyond the heater efficiency, the biggest issues with heating a Defender is air leaks and insulation. Fixing those issues is a critical first step.

Z.G said:

I watch my temp needle drop to 25% when not under load, it definitely doesn't produce enough heat when it's sub 30s. That's with a radiator muff

I will say the larger issue is sealing the cab, it was much more livable in the tdi Disco than it has been in any tdi defender I've been in

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I drive down to -40 with a heater than has 2.5 times the heat output as stock and it will cook you alive. The air burns your leg. No radiator muff. Radiator muffs are bandaids for leaking thermostats.

Overlander said:

no, but it might until I finish the install. Once complete, it designed to run the AC and heater at same time as a deliberate function, with the AC being a dehumidifier for the cabin. It's specifically addressed in the manual.

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You can't run the AC in the winter to dehumidify. The evaporator would plug up with ice quickly. You can probably get away with it in teh UK, where it does not get cold, but anywhere with actual winter, you are screwed.

Personally, I would construct a fresh air flap. Connect it to the fan speed cable so that you can open and close it. That solves the winter issue. I have no idea why they don't do this with the original design.

TexasD-90 said:

What heater are you using?

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A really big one.