Is there a fan to increase the amount of warm air?

[oregonmon]

I think I understand the "passive heat" concept. Pull up on the two levers for full heat and slide the heat lever on dash to right to defrost, which is what I'm always trying to do now with cold and rainy weather.
But is there supposed to be a fan control for the warm air. If I slide the fan switch on to the right than it's just fresh air right, the cold air takes over and the hot air is gone.
Am I missing something or is this just another quirk of the goofy HVAC system?
THanks ya'll.

[HarryD]

Originally Posted by oregonmon

I think I understand the "passive heat" concept. Pull up on the two levers for full heat and slide the heat lever on dash to right to defrost, which is what I'm always trying to do now with cold and rainy weather.
But is there supposed to be a fan control for the warm air. If I slide the fan switch on to the right than it's just fresh air right, the cold air takes over and the hot air is gone.
Am I missing something or is this just another quirk of the goofy HVAC system?
THanks ya'll.

Ryan,

Does your car have an electric blower in the engine room that is connecd to the heater ducts or does your motor fan provide the air flow?

In my '73, they used the blower for the engine cooling to also provide the hot air to the cabin. As a result, when my car is idling, I get very little air flow until I get to 3000+ rpm. In later models, they added a separate electric fan to provide hot air to the cabin regardless of engine speed.

A photo of your engine compartment can help us verify that ou have the setup for a separate blower or not.

[khamul02]

One thing I have been thinking about after backdating my heat is adding footwell blowers found in later cars. I don't really need them in Mississippi but they might be nice to have in a super cold day

[javadog]

On a '79 SC, the only fan in the heated air supply system is in the engine compartment. Check to see if it is working. If so, that's all you're going to get, unless you modify the car. If your car were equipped with the automatic heat option, you'd have a little control over the fan speed. Since you say you have two levers, your car doesn't have that option. Later cars had additional blowers in the front footwell area. Some of them also had fan controls.

I'd suggest you use the heat and not the fresh air. Leave the fresh air levers off, to the left.

JR

[spuggy]

I have no electric engine blower, thus hot air to the screen is soley provided by the engine fan.

The legend on the dash vent controls says to switch off the cold air flow altogether for "Max Defrost", but I find that increasing air flow with the hamster wheel works better for initially removing misting from the inside of the glass, even if the extra air is fresh and thus cold.

If the "misting" is heavy enough to be a layer of water droplets, you're better off wiping it off.

YMMV.

[3.2 CAB]

The engine area heater blower fan is a one speed fan. The only way of controlling the heat, is with the levers between the seats. The higher you pull the levers up, more heat will be directed to the cabin, the further down the levers are pushed, the amount of diverted heat will be less. If you still have the engine area heater blower fan, and you have both levers in the fully "UP" position, you should have ample heat. if you don't have heat, the blower may be dead, or the flapper boxes are not functioning correctly. If you are only getting a small amount of heat in the cabin, it sounds like the blower motor or the heater control valves"flapper" or not operating correctly. I don't really think that a 1979SC actually had "passive heat" it is proactive, when the levers are pulled upward, two functions happen:
1. The heater blower motor should come on
2. The levers also start to move the "flapper" doors, from being inactive to being active according to ow far the levers are pulled up. The higher they are = more heat, the lower they are=less heat.
Hopefully this jumble of information helps. Good luck!!

[tcar]

Your car came with a blower fan. When you pull up the red levers you should hear the fan come on (with ignition on). Pull levers up, go back to the engine compartment and see if it's running.

There's an accordian black plastic hose on the left side of the engine compartment that goes up to the fan. Also, a corrugated hose looping over the engine cooling fan going up to the heater fan.

The fans often fail at this age. Could be: bad fan motor, fuse or the fan switch at the red levers.

Or...

The heating system may have been 'backdated' at some point and the fan, the plastic accordian hose and the hose over the engine fan will have been removed.

If it hasn't been backdated:
Check the fuse.
Check to see if the motor on the fan works (unplug it and run 12V to the prongs).
If those are OK, it's the switch, which may just need adjusting.
If it works and there's not hot air coming into the cabin (should be a pretty good blast), then the
flapper boxes are not working.

[oregonmon]

I'm wondering if the fan is not running. That's what I'll check. You guys never cease to amaze how easy it is to get great input.

[imcarthur]

oregonmon

Here is some info The Mysteries of Porsche 911 Auto Heat. There is some info for manual heat too. Also see Troubleshooting - AutoHeat.

Ian

[HarryD]

Thanks to RWebb, we do have the factory explaination as well :

It goes like this:

"There have been several questions about this recently, so I thought I would post the Official Factory Explanation:

Subject: RE: Heat Control FAQ for Pooschey


Q: I just bought a Pooschey 911 and can't figure out how to make the heater work -- or the fresh air either. Can you help me?

A: Sure, I can help you. The ventilation system requires that you operate 4 levers to make it work. 3 of the levers are on the dash, and the other is between the seats on newer Pooscheys there are 2 levers between the seats).

The top lever on the dash actually does several different things (remember, it is a fiendish German device, just like the rest of the car). Pushing it to the middle opens the dust ports leading to the windshield (see below for operation of fogging machine and oil mist spray device). Pushing it to the right past the middle also activates the rattling noise-maker device. There are three loudness levels to choose from. Pushing the lever all the way to the left is used to jam the cable so unauthorized personnel cannot operate any of the devices above. The lever also enables the automatic heat exchanger signalling device -- when opening it spews rust particles on the windshield, you should replace the heat exchangers. Also, if opening it causes you to immediately turn blue or purple (not just hair, but skin color) and become unconscious, you (or your estate) should definitely replace the heat exchangers.

The second lever from the top controls the lights on the White House Xmas tree. Move it to the middle to turn on the lights, and all the way to the right to fire 4500 Megatons of Nukes at Iraq.

The bottom lever on the dash is used to replace the windshield when it becomes scratched or pitted with rock chips. It also determines how much hot air goes to your feet as opposed to your head. For example, let's say the engine is completely warmed up and the hot air is burning your feet. If it's a cold day, you can flip the lever to the other side and shoot hot air onto the windshield so it cracks and shatters. Then call your insurance company (you do have insurance, don't you?)

The lever between the seats controls the oil mist spray device. When the engine is warmed up, this lever allows you to blow oil mist into the passenger cabin. Using the top dash lever lets you select whether you want the oil mist to coat the inside of the windshield or to just circulate around your feet. On a newer Pooschey, you have 2 levers on the floor between the seats. The left hand lever lets you open the left side vents which are aimed so they burn the feet of the person in the right hand seat, and the right hand lever lets you open the right side vents which are aimed so they burn the feet of the person in the left hand seat. Of course, each lever will also burn just the tops of the feet of the person in the other seat. If you are driving in the rain (or even stopped in the rain after the car has broken down), these levers also let you spray a fog of water vapor on the windshield, so no one can see in or out of the car -- sort of like privacy glass."

[burgermeister]

The RWebb explanation : Hee hee heee .. good one! I love it!

If it works reasonably well, the stock heat in a later 911 should melt your shoes while driving. I can drive with open sunroof on a 50 degree day without a jacket on and be quite warm (the 88 does blow heat out of the side dash vents also, though).