IcemanG17

I haven't looked that closely at the controls...but I would imagine its not that hard to take the existing unit apart....and extend-move the controls to something you like...maybe fabricate a new control panel out of plastic...then have it covered in leather laser etched by Paul Champagne to some custom design you make? Shoot even the stock control panel upgraded by Paul would be killer!!

Don Ashe

Sure. Keep in mind this is for an '84. I'm not sure what other years are like.
The 2 sliders are what, to me, make the panel look so dated.
One slider turns a sector gear which turns a gear on a potentiometer which sets temperature. That's the easy one, you just unsolder the pot and move it to your new font panel, then wire it back to the original solder pads. The only hitch is the max heat and max cool micro-switches. One goes at each end of travel of the original slider, so I just made a cam and mounted two microswitches 270 degrees apart(that's the travel limit of the 2.2 k pot) so they actuate at full heat and full cold settings.

The switch is a bit more complex. The slider moves a contact strip across 6 pc board traces to make and break contacts. A simple rotary switch won't do the job unless you want to add some relays and such. A cam switch is made to order for this.

The switch logic is like this(you'll want to view this in a fixed font):
The longest trace is common (pin 10,iirc)
and connects to:
pin 1 2 9 15 11
----------------------------------
off 0 1 1 0 0
all 0 1 0 1 0
dn 1 1 0 1 0
bth 1 0 0 1 0
up 0 0 0 1 0
def 0 0 0 1 1

So you need 3 cams and 4 microswitches to cover all 6 positions.
Cam a has a single notch to actuate 2 switches 270 degrees apart.
The first switch has pin 15 is wired NO and pin 9 is wired NC.
The other switch has pin 11 wired NC.

Cam b is for pin 2(defrost) and allows it's (NC)switch to close in positions 1,2 & 3.
Cam c is for pin 1(footwell solenoid) and has notches from position 2 to 3.

The switches are wired back to holes drilled in the original switch traces.
I'll try to post a couple photos when I have a chance.

HTH,
-don

Hilton

Interesting.. I've been considering the same, at least as far as the control unit goes. Its on my list of things to get around to when I'm done with mechanical bits on my '89.

The most likely candidate I've come across so far is the AC controller from a '90's Audi (100/A4/A6/S6 1993-1998). Size-wise its about the same, and I have the schematics for it to match.

This is the type:
http://cgi.ebay.com/ebaymotors/1997-...Q5fAccessories

Its functionally right, and is the right size - I can measure one first-hand on Friday as there'll be one visiting then, but its similarly sized to the 928 HVAC control (i.e. slightly narrower than a single-din radio). Its also not too new, so is able to function without ECU inputs, rather than some of the more tightly integrated modern ones.

I've gathered the schematics and system pics for it - for the curious, they're in a zip file here - a bit messy, but you should be able to make sense of which files relate to which diagrams:

http://users.on.net/~hilton/Audi_Climate_Control.zip

Its not uncommon for people to retro-fit this system to earlier VW/Audi cars (VW Corrado's, Audi Quattro's etc.).

BC

Man. You lost me at "complex" Rebuilding transmissions, engines, - that I can do. Its the wire stuff that confuses me, and honestly why the car is not moving forward quickly - the next step really is to start wiring stuff up.

BC

Thanks. I will look at taht.

Alan

Actually thats a dual zone unit - I don't think there is any reasonable way to interface that to the 928 HVAC.

What Don proposed of adapting the exiting design to new controls makes more sense. E.g. find an HVAC control head that physically fits and uses rotary controls - strip out the guts - and use the mechanics to host adpatations of the current head unit design.

However I'd not use the actual head unit... Its easy to adapt a potentiometer/resistor network for the temp control, you do need the limit switches as noted. Its feasible to adapt a standard 4 posistion multi-pole rotary switch for the flap controls (with diodes) assuming you don't want to just exactly replicate the Porsche functionality - which I certainly wouldn't (Hint its too crappy). So add a few dedicated switches (AC, Recirc & Defog) and you are in business. primary controls = 3 rotary control *****: fan speed, temperature & 4 way flap posistion (Vent Only, Defrost, Footwell & Bi-Level).

Advantages of control change: Recirculate as Needed, ~maintain 1 Button Defog (better)

It becomes mostly a mechanical exercise...

Alan

dprantl

What dimensions are you working with in the fender? Will 12"x14" fit?

http://www.ackits.com/merchant.mvc?S..._Code=Parallel

Dan
'91 928GT S/C 475hp/460lb.ft

BC

I looked at it again last night. It looks like there is just the electric motor for the blend flap, but the rest are vac operated with the switches - 12v can control those right?

BC

\

Let me go measure again.

Hilton

Alan, its not a dual zone unit.

The left panel shows temp, the right LCD shows fan speed/auto/vent direction. I had one in a '98 Audi A4, which is why it sprang to mind. In 1999 Audi switched to dual-zone units.

The only bit that concerns me is the slippage detection on the compressor belt - Audi compressors provide two signals on two separate wires, one is a reference sensor that pulses 4x per revolution, and the head unit calculates belt slippage and shuts off the compressor if it detects above a certain percentage. I'm reasonably sure it can be fooled using a multiplier on the rpm signal to always assume no slippage, but need more investigation.

Putting it in should be a wiring exercise - bit fiddly but I think its doable. Part of the attraction is that it also controls vacuum actuators - the relevant Audi setup uses them for recirculate.

I'll take a photo of it in operation tomorrow (family member who bought the car off me is visiting), and some measurements, and all will be clearer It may not work, but its the most likely "modern" control interface I've come across that is a separate unit, is fully electronic (no dial controls), and has the correct match for 1:1 of functionality, hence it was on my list to investigate in a few months.

dr bob

Brendan--

For the AC condenser, I'm not sure that you want to go much smaller, especially if you want to maintain the cooling capacity that's there now. If you decide to go with a condenser that has half the frontal area, for instance, you'll probably want a 4-pass exchanger (vs factory 1-pass) and still need to figure out a way to increase the air mass you use to pass off the heat.

Somwone suggested the Pantera piece, which really isn't much smaller than what you have from Porsche. There are some short (vertically) F-car units that are closer to hang-ons (literally!) but give AC performance that's only aceptable in our winter months here. 80º+, fugetaboudit. Net AC capacity is very closely tied to how much heat you can shed, specifically the condensing temperature (and related pressure). Lower there means lower suction pressures at the same mass refrigerant flow, which mean more heat can be moved.

BC

Well, as I mentioned I may have to put two small ones in. Its just not a good idea to put it infront of the A/A intercooler. Nothing goes infront of that except some very strong mesh to protect it.

So can I go through two smaller ones?

BC

I measured. If it can't be laid back at all, I get about 10x10. If I can lay it back, I can possibly do like a 9x12 or 13.

No, not big. But 9x12 and 9x12 = is over 200 inches adequate - if separated by half in each fender?

Alan

Well I'd say adptation will still be quite problematic - the issue is the temperateure control - realistically unless you are willing to retrofilt the whole flap motor from something else you pretty much need to use the Porsche temperateure loop and flap motor control unit.. its not too hard to build an eqivalent to the head unit - Porsche provides a full schematic for it. NB The late model version of the schematic is almost unchanged from the early cars version but is drawn to be easier to understand functionally.

This is still more complicated than it seems...

Alan

Don Ashe

I've got the console half taken apart at the moment, so I'll try to take some pics of the cam switch. Keep in mind that the cam switch is only one possible way to do it. It does take some fabricating, but that's what I like to do!
If you want a more straight forward approach, you could use push button or toggle switches instead. One switch would be a dpst on/off and connect pin 10 to 9(off) or 15(on). The other side of the switch would connect pin 10 to an spst which would switch defrost mode on and off. On would connect to pin 11 and off would connect to individual switches for up(pin2) and down(pin 1).
If you really like switches, you could add ones for max heat/max cool instead of using the cam switch, since they bypass the pot.
The switches need to be rated at least 1 amp at 12vdc. There are back EMF protection diodes built into the PC board, but the solenoids draw up to 300 ma each.
Let me know and I'll upload a schematic.

Controlling with a computer is definitely doable. I chose to use switches because I prefer manually controlling those settings. I only use the car computer to play music , access the web, my calendar and that sort of thing, and eventually I'll use it with the Megasquirt for data logging/viewing.

To drive the hvac controller via computer, you would need to wire something like fusion brain to the contacts instead of the cam switch. It could also control the blower. The pot would need to be replaced with a digital pot or driven by a stepper motor.
This is all predicated on keeping the stock control box and controller board logic, inside and outside air sensors, etc.

Hope this clears up some of the fog...
-Don