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Heater / A/C box
The Lotus heater & A/C setup was not very good. The first major problem was that the heater had hot water flowing through it the whole time. This would a) make the engine warm up much slower and b) allow a significant amount of hot air into the cabin all the time, because of the second major problem - everything was contained in a flimsy, leaky plastic box. To stop the hot air reaching the cabin Lotus relied on two steel shutters - which did not fit that well. Also a lot of light foam was used to seal gaps, which was already disintegrating into powder. Finally, the drain for the water dripping off the A/C evaporator was useless and the whole front cavity showed signs of water sitting in there. Incidentally there is a Lotus service bulletin to fix this by drilling some holes in the front floor - not a good solution by any means.
I made a replacement 'climate box' out of aluminum to mount the A/C evaporator and heater core. The air flow passes through both the A/C evaporator and heater core all the time, but the heater being controlled by a heater valve, as god intended. Attention was paid to air flow, and the whole thing was insulated inside and out with foam & rubber.
The Lotus copper heater core was junked, and I used a larger aluminum core from a RSX. The blower was mounted to the side of the box, so that air passes through the A/C evaporator and then through the heater core, which is placed at a 45 degree angle, and out the top of the box to the interior of the car.
The whole thing sits on soft rubber feet to both keep vibration down and raise the box so that water from the evaporator can be drained out correctly.
In the end the final product looked like something an astronaut would carry onto the space shuttle, but it had to be done and presumable will work when the car finally runs.
The interesting thing is that despite the Lotus box being made out of flimsy plastic, and my replacement being made from fairly thick aluminum with a lot of insulating rubber, the new box was about 1 lb lighter than the old box. Removing the steel shutters probably made the difference.