Orbitguy

thanks much

jeff

Mark Salvetti

Hi Jeff. Welcome to Rennlist! Yeah, you won't be getting any responses from the OP.

Lots of good info in the material posted by Mike Murphy (above). There was also a recent thread that delves into the operation of auto heat and the heater boxes: https://rennlist.com/forums/911-foru...ing-noise.html

If between your seats you have two levers with red plastic *****, you have manual heat. If instead you have a box with a dial that goes from 0-10, then you have auto heat. It may or may not also have a single lever with a red plastic **** - that is a back up in case the auto heat function fails, but not all cars with auto heat have that.

If you post some photos of your controls and also your engine bay, that will give us more info. The important thing to know is a stock setup has the two heater boxes under the car near the rear shocks. There is always hot air flowing to them from the engine. If the flaps are closed, the heat is dumped under the car. If they are open, the heat makes its way to the cabin through hoses that pass through the rockers under each door. There are also various fans that boost the flow of air. Assuming you have manual heat, the two levers should open and close the flaps. They also activate the heater blower in the engine compartment (assuming you still have that, sometimes they are removed).

The heater boxes take a lot of abuse from the elements, and it isn't unusual for them to be rusted open or closed. That could be your main issue, but if you have auto heat, it could also be malfunctioning and leaving the flaps open all the time.

Hope this helps,

Mark

parkerfe

my 88 cab has the two levers and 4 speed fan speed dial on the console.

Mark Salvetti

I think that is still manual heat, but they added the dial for fan speed in the Carreras.

The two levers indicate manual heat. See this thread: https://rennlist.com/forums/911-foru...-87-911-a.html

Mark

theiceman

should be an easy fix then

could the dial be for the footwell blowers ? i have an SC so i dont have those .

eflight

Dial that goes from 0-3 is manual heat and is for control of the footwell blowers.
Levers in front of it turn on the engine blower and control the temp of the heat.
The power to the engine blower powers a relay that enables power to the switch to control the footwell blowers. If the levers are down all the way the footwell blower is not powered because there is no power to the engine blower.

theiceman

so sounds like they resolved the issue of my shoes melting in my SC then.. lol