Oh gee's, I just re-read the original message. You guys are talking condensor capacity not evaporators LOL.
It would be the same radiator and condenser across the defender/range rover classic/discovery range wouldn't it ? If so, the factory condenser on the range rover classic works adequately. I'd find the biggest most efficient condenser I could find an use that (though the local A/C guy here who is really good uses range rover classic condensers on a lot of his aftermarket installs as he reckons there big, efficient and cheap). What are the high side pressure your running like ? It's possible your clutch fan is dead if the A/C stop working at idel in traffic (and the condenser fans aren't working ).
The car in my avatar? You must have found my threads over on aussiefrogs. That car is a import, my father bought it from the UK back in 1996 so it had no air-conditioning ( it's a Citroen CX2500 GTi Turbo 1 Series II ). I moved a system across from a 1978 model that had front and rear evaporator units. I had to fab up the brackets to fit the Sanden SD7 compressor. I asked the local guy to order in the biggest most efficient condenser available and fitted. The evaporator unit in the boot works well. It can ice up the lower 1/3 over the rear window. the front unit sucks as always (as the heater box design is crap).
If you fit a rear/2nd evaporator unit, fit a solenoid valve to it (available from Toragos at your local wreckers that have rear A/C units). Otherwise the rear unit will turn to a block of ice .... well mine will on hot humid days. If you turn the A/C off for 5minutes, you get 1/2bucket of water from the rear unit dumped on the ground and it works again).
I have the rear unit solenoid from a Torago sitting on a shelf in the shed..... one of these decades I'm going to get around to fitting it.
If you have EL fans fitted, I'd wire in a trinary switch and kick the radiator fans on full bore from the high pressure switch as well.
seeya,
Shane L.

