While trying to get my 71 Malibu ready for winter i've found that the heater blows fuses after about 5 minutes. so while looking up under the dash , i found two big fuses about 1"x1 1/2" with three prongs each and being somewhat color blind I beleive the wire colors to be lt. blue, orange and maybe brown, THE NUMBERS ARE 3996203 and 3996204 with the brand name LITTELFUSE INC. Can you tell me what they are for and where can I find the ground wire?

Did you get your heater working? I didn't realize what you were talking about until today. Assuming you have an A/C car, the devices you are talking about are probably the anti dieseling relays unique to 71. Not sure what ground your looking for. If the blower motor lube is dried out and the motor is running slow or dragging it can blow fuses.