Mike Valliere

I have an 81 SC Targa that was originally fitted with A/C but the A/C has been removed. However the fan and heater controls are still the same. According to my manual the fan motor is located in the engine bay but until the switch started burning up It sounded as though there was another motor up under the dash. has any one experiance this before? The heat worked great until the switch burned up. I would also like to know how difficult it is to replace the heater controls on the dash. Any and al help welcomed.

Thanks
Mike
81 911 SC Targa

DGaunt

There is a fresh air blower in the trunk that is sort of under the dash too, at least froma sound point of view.

The rear fan is operated by two microswitches in the heat levers via a black relay on the rear fuse panel.

Hope that is a start.

Paul Conquest

The AC and heat are independent. Regarding the heating system operation, ambient air is pushed through the heat exchangers by the engine cooling fan. At higher RPMs this works great ... in fact, at 4,500 RPM there should be enough heat to melt your shoes. However, at lower RPM (below about 3,000) there isn't sufficient flow to keep the cabin warm. Hence, the engineers at Porsche added an assist fan located in the engine compartment. There is also a blower motor in the front, but the front blower is for fresh air only and is not directly involved in heating the cabin (in fact, its usual purpose is to cool the cabin).

If your problem is a lack of heat, the first question is "Is any warm air flowing at higher RPMs?" If the answer is "No", the problem is most likely the control boxes located under the back seat and adjacent the transmission (these are purely mechanical devices operated by cables connected to the floor controls, and some WD-40 or an adjustment might be all you need). If the answer is "Yes", the most likely cause is that the heat assist motor located in the engine compartment is not working. The dash mounted controls have no effect on this motor. The most common problem with the assist fan is that is subject to rather excessive heat and therefore premature failure, so you might want to check the condition of the fan motor.

If you need to replace the motor and want to save some money, there is a great swap using a Granger motor with details here http://forums.pelicanparts.com/showt...hlight=skillet .

As for the assist fan circuit, power is delivered to the motor through a fused relay located with the ignition controls on the inside left fender. The fan relay is operated by a ground signal from the micro-switches on the base of the floor-mounted heater control levers inside the cabin.

Hope than helps.