Fresh air and heater valve system update/backdate

[TargaWoods]

Tried scrolling the forums, figured I’d make a post.

Just finished heater backdate on a 78SC. Wondering if there’s a simplified system or upgrade for the trunk air system with the fresh air fan.

I have to get inside of the fan and clean it regardless Because the motor whines while it spins and sometimes stops while it’s supposed to be on.

It had me Wondering if I can rip out the old system and simplify the ducting/valve system to still get hot air, and fresh air?

Is this upgrade a thing? Or do we just refurb and keep the old Porsche system.

[Walt Fricke]

I think you can forget about cleaning anything curing the whines. Its low quality bearings are shot. The normal repair is to replace the assembly. The motor and fan part aren't all that expensive, and I'd recommend you get the motor with fan attached, as the old one doesn't want to come off its shaft.

No way, really, to simplify anything here. It is actually pretty clever if you read the driver's manual and learn how to use it (took me a long time to realize that). Pita to do the replacement work, as the clips and so on are hard to work with. I gave up and used small zip ties to put the plastic parts back together.

[SkiVT]

I recall someone saying you can add a T to the green path into the blue path through the center air vent. Still need to fix the fan for good airflow.

[targa80]

If you are only looking to have a heat source and a fresh air source with no ac then you could remove the two blend valve assembly’s and reduct to suit your needs. You can purchase a new fresh air motor for under $100 and it is not hard to replace. Your heat duct can be run to the windshield vents and to the two open holes where the blend valves used to be. Heat would be controlled by the two levers behind hand break. The heat slider would no longer function since the window defrost would be permanent for heat. The fresh air blower can be ducted for the center, side vents and also the bow tie vent.

If you plan to keep ac then you are in a different animal all together. Either you go with the original belt driven or you convert to an electric ac like the Electrocooler.

I went with the Electrocooler and deleted the two blend valves. The top slider is the only functioning slider for the three speed ac fan. I have two post on my installation and mods I did to the fresh air and ac system. Just do a search under targa80 for the posts.

[EC900]

Here’s a link frankc provided a nice write up that helped me figure out the ac/vent plumbing on a non-ac…I had dealer installed “extra hole in the smuggler box).
Dealing with those ring clips (Corbin) needs extra caution, using anything but a dedicated Corbin clamp pliers with result in injury as these will shoot out of ordinary pliers…wear safety glasses if you trying this! Good idea Walt, ditch they Corbin clamps on reassembly and use small zip ties - unless of course you have a set of Corbin clamp hose pliers.

Retrofitting non-A/C ventilation ducts

[Peter M]

I've had good success in curing bearing noise on these fan motors by soaking the bearings in oil overnight.

Just avoid getting oil on the commutator and brushes. Recovered 4 motors by this method to date.

The smell of oil in the ventilation system dissipates in a week or two!

[FA-18C]

The HVAC and fresh air system seems to be the "flux capacitor" of the 911s, designed during Octoberfest. I can almost see the engineers giggling over it...

[EC900]

#1 @FA-18c…Even with the instruction label on the glovebox door, I still haven’t mastered the system, fiddling the sliders and up and down on the center levers in traffic is like working a Tony Beets gold dredge.
My fresh air blower motor (bearing) would squeal if not run for a long period, eventually quiets down on its own. So now I leave it blowing all the time, just keeping the vent louvres closed and redirected.
Somewhere I read that it’s possible to oil the bearing by drilling a small hole in the blower case. I can’t find that post, @PeterM, any suggestion how to oil the fan motor in place?

[FA-18C]

My fresh air blower is noisy, similar to my 72 Targa, so 16 years later, still sucked. They just added a blower for the AC, two in the footwell, and another in the engine compartment for heat. I never had a problem with heat an any 911 - fresh and cool air have always been the challenge.

I am a couple of years away from taking the plunge, but am hanging a heavy hope on the Classic Retro rig. Gets rid of the crap in the back, cleans up the engine bay, and removes AC hoses running back and forth all over the chassis. It may offend the purists, and I have 100% confidence that a Griffith system will freeze me out, but I want less stuff.

[Walt Fricke]

The driver' manual can help. I took a December trip from Boulder CO to St. Paul and back. With the heat even on its lowest setting via the two handles by the parking brake I would eventually be too hot. I'd crack the window to cool down, but soon would be too cool, etc etc.

Reading the manual (my excuse was that this was a gray market car and the manual was all in German, using words we never saw in German Lit) I figured out that blending some of the fresh air from the cowl grill allowed fine tuning, and I never had a problem after that.

[FA-18C]

I removed the AC compressor, but the fan works and provides air to the upper vents. I plan on leaving the front condenser for future AC install. Just wish I had more air. I need to jump the wiring in the back as recommended in other posts for footwells, but heat is not the problem.

My 70E was easy - pull levers for heat, open side and rear quarter windows for air...

[nztroy]

Any idea where to get the under dash vents from? Adding a/c to a non a/c car and dont want to screw up the dash…

[EC900]

@nztroy - keep in mind there are two different styles of those dealer installed AC consoles. Mine is deleted and left an additional smaller hole cut into the tub that lead from the smuggler box blower. The other is plumbed using specific tubing to distribute from the center fresh air vents. These units will also require removing the stock need pads. Also, the vent louvres are very fragile, often break or broken in used units. These old units don’t pop up for sale often as I was once looking for parts to keep mine a stock look, maybe unobtainium has one in their inventory.

Here’s a pic of what was once under my dash…

[RSTarga]

Thats a VW of America unit, very good flow. It's what I have.

[EC900]

@RSTarga - yep, VPC, when I took it out (due to being cracked in a few places) I was tempted to split the clamshell design of this console and add some Kydex diverters inside to better control the air flow since this unit is wide open most of the air flow is directed at the front two vents. The fresh air vent system is a separate blower, so the entire VPC was just dead weight. I’m running w/o ac for now. Still the old VPC is terrible unit, but keeping the parts (stored) for originality.

[Coastr]

The whole system is one that suffers from incremental fixes instead of redesign. It’s easy to forget now that nearly every car has auto climate control - but back in the day all cars relied on the driver to figure out the right blend of recirc and fresh, heat and AC to get the right climate inside. Much like manual gearboxes, manual climate control is pretty much gone. Like anything manual, it is possible to get it perfect with just the right combination of lever settings. But it’s more like operating a model T manual than a 6spd h pattern with power assisted clutch.

Key things are knowing how to get the hot up or down, and how to mix in fresh with hot (all hot is technically fresh).

The mother of all DIY projects would be building a climate control panel to replace the sliders. Theoretically possible with an auto heat box to work the levers and something to pull / push the Bowden cables, coupled with the classic retrofit fan box.

[Bucketlist]

My 2 cents: I'm trying to understand Auto Heat and have read most of the old threads. I have taken the auto heat control apart, fixed some broken pieces and plugged it all in. When I turn on the ignition the (single) lever comes up powered by the servo closing the flapper boxes. The knob on top has no effect. No way to open the flapper boxes and turn off the heat other than disconnecting the rod for summer or installing a switch to bypass the control. The cabin sensor seems to work but no readings from the flapper box sensor. The good news is plugging in the auto heat control has made the dash controls work. Now that my fan will run I may need to replace the noisy motor and find the duct for the center vents.
Several years ago I installed Retroair complete system in my non a/c car
If someone is thinking of doing this you might take a look. Retroair is no longer in business but there are other systems out there. AC in the west Texas summer heat is the best improvement I have made to the car in 10 years.
Good Luck!