how do I know if the heat regulator 'tween the seats is working?

Second question,

My car has that heater regulator knob betwixt the seats. It doesn't seem to do anything, regardless of the position. What does a functional one do? How do I ascertain if mine is not working?

Last, I've never driven my 911 in severerly cold weather before. However, it looks like it might get some snow action this winter. I'd love to hear about peoples experiences driving air-cooled 911's in ice, snow, etc. What's the best advice about defrosting, etc.

Dave

Unfortunately, the heater systems in 911's is not particularly good - it seems that Porsche designed a great sports car and then, as an afterthought, grudgingly decided to install a heating system !

The black box between the seats contains a hideously expensive control unit consisting of a small circuit board, a servo motor and some linkages. Also, on the front dash near the steering column, you should see a round extrusion with two elongated slots in it. This is connected to a plastic pipe which routes underneath the ashtray where it is connected to a device which draws air into it. There is also a device called a thermistor in there which changes it's resistance dependent upon air temperature.

underneath the engine there are two 'flapper' boxes attached to the heat exchangers whose job is to divert hot air from the exchangers into the car. The boxes have circular 'valves' with cut-outs in them - normally when the heating is off, the cut-outs are open and the warm air exits the car at that point, the higher the setting of the control switch, the more closed the valves become, thus diverting the warm air along the pipe and into the two footwells in the front of the car. These footwells contain a motor each to assist the airflow in extreme conditions - these motors are prone to seizure and have their own in-line fuses so it's worth taking off the covers and checking them out. Now, the purpose of the control unit between the seats is to regulate the warm air and keep the cabin temperature constant depending upon where you have told it you want it - in practice it seems to have a mind of it's own ! When you switch the control unit fully on, the footwell blowers should come on but only for a short time. If they don't it doesn't necessarily mean they are broken since the system may have decided that fan assistance is not necessary. There is a procedure in the factory workshop manual to test out the system but it's too long winded to publish here but I hope I have given you enough to be going on with.

Cheers.

If your car has the knob that you turn that is on a raised part of the center console(ours does), than it controls a servo type of mechanism that moves the wire connectors to the heater boxes in back. There should be a small inspection door in the side if the center console under the knob and if you open it, then you can see if the actuator wires from the control to the heater boxes are hooked up. One of the ones on ours had the connector break and if is easily fixed. I think that is also where the temp sensor for the regulating the temp is. Good luck.

Hi Dave, you never mentioned what year your car is. If it is a car earlier than 1974, then the knob that you are pulling up on is directly connected to a cable that runs back to two heater boxes located above the heat exchanges. The heater boxes have been known to freeze from lack of use and can sometimes be saved. The cable that opens and closes these boxes has been known to snap. In either case, I would replace the boxes with stainless ones and run a new cable. If the car is newer, I am not sure about the system, so I would look to the other responses. Good luck with the problem. P.S.: Running the car in the winter is not bad, but if you have a deep front spoiler, it could act as a snow plow.

Our 83 SC had the auto climate control that also had a mind of its own. Rather than screw around with it, I found a dual heater lever/hand brake unit ($20) from a manual-heater system at our local swap meet (Potomac Region). Essentially, the electronic system was yanked out and replaced with the manual system. I prefer the manual system as now I can keep the right side fully open (heat open) and the driver's side slightly opened so I don't roast my toesies. Of course we all know this basic heating system goes back to the beetles and 356s manufactured during the 50s. Except, we had a wheel to turn rather than a lever to pull up. Good luck.
chuck in Reston, Va