i have a 85 760gle turbo diesel saloon the heater motor switch has 0 to 4 rotary type the heat or air con slider has the ac positions on the left then cabin then demist if i put the slider into any ac position or demist screen it blows the fuse 8 as if the blower motor is going to boost the motor works in all positions on normal heating usage its only if i select ac or windscreen demist please can anyone help is there more than 1 blower or does it have a boost position terry whyton