Engine shuts down - becomming dangerous, need help !!

Hi,

i have a 96 manual diesel RR

the engine shuts down instantly when i shift down (mostly from 3 to 2)
and when the airco is on and i take a turn

a bit strange

this only happens on hot days when the airco is working hard

i guess that when i shift down, the engine looses power, add to that that the airco is working hard
and that in a turn the servo-steering needs power also

i gess that is the reason why the engine shuts down

this happens about one or twice a week but it is very dangerous cause sometimes on a roundabout
i loose power steering and power

i guess it is soe kind of electronic problem

what should be done ??

a zillion thanks for any good suggestions

I'm not sure about diesels LR/RR, but most vehicles have a idle advance
when the AC is on to keep the motor from dieing.
It bumps the rpm up one to two hundred.
On my VW TDI the injection pump adds more fuel to keep
the rpm from dropping.