Convert 1985 Auto Heat to Lever Controls?

Swoboda · Swoboda's Garage

I don't necessarily have a problem with the auto-heat controller in my 1985 Targa, but it does seem to be needlessly complex (and based on what I've read after some searches, it can be prone to failing).

The levers seem to be a simple solution.

Is it possible to (easily) convert the autoheat controller to the lever set-up?

Is this a practical thing to consider from a cost perspective?

I'm not going to get rid of my heat in the car--too much fun to drive as often as possibe--even in cold weather!

Thanks in advance for your thoughts.

Lawrence

javadog · 11-03-2010, 06:11 AM

Lawrence,

It can be done and it's not all that hard. You can gather up the parts one at a time but the easiest thing to do is to just find a complete used handbrake assembly that has the levers attached. You'll also need to change the cable between the auto heat controller and flapper claves to the two cables used with the twin levers.

JR

KNS · 11-03-2010, 09:32 AM

Somebody correct me if I'm wrong but I believe there is a microswitch when the levers are pulled that activates the blower motor in the engine compartment. You need to figure out the wiring for that as well.

javadog · 11-03-2010, 11:07 AM

Most of us ditch the auxiliary blower fan...

Having said that, that's one of the reasons to buy a complete used lever assembly. It's almost plug and play.

JR

Swoboda · Swoboda's Garage

The auxilliary blower fan is in the engine bay, correct?

So with the blower gone and levers installed the heat enters the cabin without any blower based on the amount of "opening" the levers create, right?

Just trying to understand a little better. I appreciate the thoughts.

Lawrence

Walt Fricke · 11-03-2010, 11:22 AM

Maybe in balmy Tulsa you don't need the engine mounted fan, but if you drive the Colorado mountains, or commute in Minnesota (actually, for a commute anywhere it gets below freezing), having it is really nice. Despite the fact that it craps out so seemingly quickly. Better warm air flow on the windshield.

What I'd be inclined to forego, and certainly to switch separately, are the two little footwell blowers. Those are cheesier than the engine mounted blower, and guaranteed to fail eventually. They don't just squeal and make noises, they weld themselves together, can make smoke, and will blow fuses. They are helper blowers, and while more is better when it is really cold, I don't think they add all that much.

The early 911s had no blowers for hot air. Compared with a VW beetle (or, for an extreme, a bus), they worked great - get heat from all six exhausts instead of only two. When the car is all warmed up on a winter road trip in sub-freezing weather, this produces all the heat you could want. On one trip I had alternately to turn everything off, or crack a window, to keep the heat down - though had I read the manual I'd have realized I should be using the cold air controls to mix in some cold air to balance things without all these gyrations! What, me read the manual?

But for shorter trips, or colder ones, having that extra forced air is really good. Leave work at 7 or 8 p.m., temperature maybe 10 degrees F, car sat out all day - want to keep the windshield clear ASAP before leaving the parking lot, really.

warner53 · warner53's Garage

The micro-switches on the levers control the foot well blowers, I am not sure about the main blower in the engine compartment being controlled by the same switches.

W

javadog · 11-03-2010, 11:39 AM

Quote:

Originally Posted by Swoboda

The auxilliary blower fan is in the engine bay, correct?

So with the blower gone and levers installed the heat enters the cabin without any blower based on the amount of "opening" the levers create, right?

Yes and yes. The heated air comes from air that is diverted from the main engine cooling fan and so the faster the engine speed, the more heated air you get.

JR

javadog · 11-03-2010, 11:52 AM

Quote:

Originally Posted by warner53

The micro-switches on the levers control the foot well blowers, I am not sure about the main blower in the engine compartment being controlled by the same switches.

W

Here, you start getting into the differences between years and models. Prior to their introcuction in the 3.2 Carreras, there were no footwell heater blowers.

I'd suggest that searching for "heater blower" in the 911 tech forum will pull up more threads on these things than you can read in an afternoon.

JR

javadog · 11-03-2010, 12:00 PM

Quote:

Originally Posted by Walt Fricke

What I'd be inclined to forego, and certainly to switch separately, are the two little footwell blowers. Those are cheesier than the engine mounted blower, and guaranteed to fail eventually. They don't just squeal and make noises, they weld themselves together, can make smoke, and will blow fuses.

Assuming that they have a fuse to blow. The early ones were unfused, another of Porsches little engineering screw-ups. While I'm at it, I'll mention the unfused instrument light circuit...

JR

KNS · 11-03-2010, 02:26 PM

The footwell blowers: Can one remove the blowers and just install a length of heater tubing in their place?

PS: For a Carrera not an SC...

javadog · 11-03-2010, 03:37 PM

Yes. I'd run the new hoses all the way from the sills to the distibution boxes in the trunk, instead of splicing into what's there already.

JR

Walt Fricke · 11-03-2010, 03:56 PM

JR - I didn't want to recall the call from my wife when we had a 3.2 (really fine car) saying there was smoke and the car was in the garage and what to do. She got a neighbor to pull the battery ground.

Later 3.2s had a fuse, and wiring diagrams seem to show one for all models, I think, but they lie. No way any fuse would have let things heat up enough to melt the plastic of the motor so that one of the brushes eventually fell out and broke the short circuit.