Vent/Heater Controls
 

There must've been more than one version of the owner's manual for 1977. Mine is different than my car in a couple of areas. Here's the latest; my manual shows the vent/heater control panel with two slide levers on the top level and one each on the middle and bottom levels. My car, however, has a single slide lever on the top. This top lever controls the front fan, but I don't know about the other two. Can anyone help me out?

Here's a second associated question - which switch/lever controls the rear fan (in the engine compartment)? When the two floor controls are up to heat the cabin, is there a fan boost? I can't get it to come on and trouble shooting the wiring will be tough if I don't even know which switch is supposed to control it.

Ray:

My heat control panel has 2 sliders on the top. One on the left controls the vent level (up or down) and the one on the right controls the fan.

The switch for the rear blower (in the engine compartment) is on each of the pull levers on the the floor. They are small contact type switches, and can get bent out of shape easily.

With the ignition on and a lever pulled you should be able to hear the fan in the engine compartment blowing. The wires go through the 14 pin connector on the rear fuse panel. I would check to see if you are getting 12 volts at the connector on fan, and straight wire the fan to 12 volts to see if the switch or the fan is the problem.

Good luck.

Don't know which one, but I think one of the 3 fuses on the relay board in the engine compartment is for the fan motor. Check and clean those 3 fuses.

If I remember correctly the levers change depending on A/C.

The uppermost lever controls air (to left = off) from outside. Moving the lever right lets in more air until you are now turning on the fan to aid air to the cabin from the outside.

The middle lever handles where the fresh air from the outside goes: left for lower, right for upper vents.

The bottommost lever controls heat as directly above.

The heat blower motor comes on when you pull the twin heater levers between the seats. A switch there ought to be activating the blower motor. Quick test: car off, key to accessory - pull the levers up and listen for a fan in the engine compartment. No fan means check lead to fan for current. No current means fuse out or otherwise. Current buy not motor means remove hoses to heater, unplug and bench test blower motor. Typical for these to fail.

I swapped out the switch at the levers for a manually activated switch that lets me decide when the heater blower motor goes on. Since the heat is also pushed by the engine fan I like to keep the heater blower motor off unless I really want it on.

John

Jdub - thanks, that's the one! My 77 has factory installed air, and my layout matches your description. Thanks. I think I may go with the manual switch as you described - there is plenty of heat with just the handles pulled up a bit; fan-forced might be too much.

I wonder why the manual doesn't mention this? A/C must've been a fairly rare option.

My 75 911S has no engine compartment mounted electric fan so when I want hot air, I can't run a boost fan at the same time. Some days, you really need to get the hot air moving! What's the deal?!

Talk to any of the folks (Superman) who have backdated their systems to remove the hoses and fan and see if they will sell you their parts. Then attempt to set this up in your car.

The blower motor was never much more than a fire hazard in my opinion. Just keep the revs up and you'll stay warm!

John

Jdub, do you have any pics/procedures for how you wired the heater blower to a manual switch on the dash (I'm assuming the dash)?

Matt:

It's a piece of cake. The yellow/black wire grounds current when you pull either one of the two manual levers. You simply pull that wire from the black plastic switch just ahead of the levers and extend this wire to the back of the dash. Hook it to any single-pull knob Porsche makes and you fancy and you're home free. All you need is for the knob to ground the connection. If the knob incorporates two posts, simply plumb the yellow/black to one post and ground the other post via a brown wire (typical for grounding color) to any bolt or screw under the dash.

Very, very simple to do. You can even create your own glyph on the Porsche knob you choose by poking out the transparent center piece, scrubbing the "fan" or "heater" glyph and stenciling in your own.

John

Alright, now I'm really interested :) Can you show a pic of your knob? I was going to use one of the small, rocker switches (like the headlight washer one) for mine. But I also wanted one that glows to remind me that it's on. Does Pelican sell one of those switches that glow that would fit in the rectangle holes in the dash that are covered?

I says, "Pardon"!?! :p