Is it normal for the rpm to drop when there is electric load ?? My car is exhibiting the following symptoms -> When the car is cold the idle is just fine then when it starts to warm up the idle starts to flactuate up and down and it sometime dies. When it reaches normal operating temp the idle is fine as long as there is no electrical load. If i turn on the heater, rear window heater or headlights the rpms drop, it's even worse if I turn all of them at once then the car can barely idle

. Another thing that I've observed is when idleing in place if I rev the engine to 4000 -5000 rpm and let off the gas the rpms drop to around 600 - 650 and then rise to 850 - 900. My guess is that it's some sort of electrical problem any ideas to what I should check ?
Thanks,
Joreto