I switched the aircon on and there was a small blue light indicating a electric fault, i presume and heard a sort of relay ticking in or under the dashboard.

can the HEVAC draw so much power that it will have an effect on Gearbox of cruise control???

PS: when aircon is switched on, the car blows hot air for a while then cold and then after a while hot air again..

It is a 1996 Rang Rover HSE 4.6