HVAC control head intelligence
Three Wheelin'
Joined: Apr 2004
Posts: 1,868
Likes: 4
From: San Diego, CA USA
Note that the "decision" to open/close the heater valve solenoid is made by the mixing motor. I had a bad mixing motor, and the heater valve solenoid was never energized (the heater valve always stayed open; it never saw vacuum), no matter how hot it was in the cabin, or how cold I had the thermostat slide set.
Took me forever to isolate.
Took me forever to isolate.
Three Wheelin'
Joined: Apr 2004
Posts: 1,868
Likes: 4
From: San Diego, CA USA
I would definitely be open to a freshened look for the climate control head, if someone could construct one. I like the look of a 944 with the variable sliders and rotary ***** for both temp and fan. I guess we can't have infinitely adjustable flaps with simple 0/1 vacuum pods.
Nordschleife Master
Joined: Dec 2004
Posts: 6,164
Likes: 7
From: Guelph, Ontario, Canada
Malcolm,
You are correct to a point. You would need to figure out what additional resistance was required to make a 'zero' value to the controller. Then you would be able use it like a manual system.
Brian,
I think what you are calling the setting motor is what I am calling the control unit. I think without to much trouble they can both be integrated into one head unit (with some creative wiring). My first iterations are going to be just direct replacements that are digital (up down buttons for temperature and fan speed individual radio buttons for flap positions) Then I will expand the capability.
Note that this is for 84 and later units (at least up to 91 as that is as far as my WSM's go).
You are correct to a point. You would need to figure out what additional resistance was required to make a 'zero' value to the controller. Then you would be able use it like a manual system.
Brian,
I think what you are calling the setting motor is what I am calling the control unit. I think without to much trouble they can both be integrated into one head unit (with some creative wiring). My first iterations are going to be just direct replacements that are digital (up down buttons for temperature and fan speed individual radio buttons for flap positions) Then I will expand the capability.
Note that this is for 84 and later units (at least up to 91 as that is as far as my WSM's go).
Thread Starter
Rennlist Member
Joined: Oct 2004
Posts: 10,717
Likes: 58
From: Southern Alberta, Canada
Brian............thought so.............BTDT.
Rod............I've been re-reading the relevant WSM pages as this post has went and its now actually starting to make sense. Perhaps as we wait for your new improved control unit we should re-write the the respective what is positioned where pages of the a/c pages.
Rod............I've been re-reading the relevant WSM pages as this post has went and its now actually starting to make sense. Perhaps as we wait for your new improved control unit we should re-write the the respective what is positioned where pages of the a/c pages.
Rennlist Member
Joined: Dec 2001
Posts: 25,186
Likes: 105
I have trying to figure out how to put my 78's HVAC stuff back i n the car in an "improved" manner. The 78s did not have the electric solenoids, and I will not have much of the wiring that any of sparce electric portions of the 78s HVAC controls anyway. There is no temp sensor on the 78 either. I do believe it is basically all manual.
Interesting.
Interesting.
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928 Barrister
Rennlist Member
Rennlist Member
Joined: Sep 2002
Posts: 4,772
Likes: 6
From: Sunnyvale, CA
When my '86.5 is working properly, it is really great. Truly climate control and always adjusting to maintain an even temperature. At first I cussed its complexity, being from the school of thought that simpler is better (need AC? roll down a window. less weight that way.) But once I had it working, I was hooked. Then it was a matter of educating myself about the proper means of modifying the controller with the external relay that fixes and prevents failures. Now if I could just get around to re-installing my new compressor.......everything would be fine.
My 914 has the simple system as Heinrich describes. On that car, it is fitting. Simplicity and lightness and all fun. But the 928 has changed my way of thinking about long distance travel. I even cussed the power mirrors when I first bought the car, but now I love them. Guess I've become a gadget man.
Keep us informed of your progress, though I am happy with my current (factory )system since the controller relay issue was solved.
My 914 has the simple system as Heinrich describes. On that car, it is fitting. Simplicity and lightness and all fun. But the 928 has changed my way of thinking about long distance travel. I even cussed the power mirrors when I first bought the car, but now I love them. Guess I've become a gadget man.
Keep us informed of your progress, though I am happy with my current (factory )system since the controller relay issue was solved.
Rennlist Member
Joined: Jan 2004
Posts: 12,620
Likes: 8
From: Boulder Creek, CA
Originally Posted by heinrich
I'd prefer a simple pushrod cable replacement sytem. Open, shut, on, off. Manual. Driver controlled. Never fails.
There is no such thing as a system that never fails, IMHO.
928 Barrister
Rennlist Member
Rennlist Member
Joined: Sep 2002
Posts: 4,772
Likes: 6
From: Sunnyvale, CA
Yup. There is truth in Dave's statements. My 914 has suffered cable failures, and so has my Rabbit. But they are really easy to isolate and fix. Simplicity is the key. The problem with cable "on-off" systems is that you are always adjusting them. A little too much heat......push the lever one way......a little too much cold......push it back the other way. And on and on.....! They work better than no system. And I know because I have driven my Rabbit across the country in through the mountains of Colorado in the dead of Winter at 5 degrees below zero with an inoperative heater core. That was fun. The later systems are so much more sophistocated. (translated: complicated). But so are our engines compared to the '60s and '70s engines that worked .....for awhile.
Thread Starter
Rennlist Member
Joined: Oct 2004
Posts: 10,717
Likes: 58
From: Southern Alberta, Canada
Agreed that the HVAC system probably does work very well when fully functional and it would easier to consider a manual system as replacement than fix the OEM but as we now somewhat understand the 'workings' of the system I'm giving it a shot (again).
The outside and inside temp sensors are simple electronic devices I believe..............anyone know testing proceedure, fixes, upgrades? I'd look it up in he WSM's but it might take me the rest of the day to find it!!!
The outside and inside temp sensors are simple electronic devices I believe..............anyone know testing proceedure, fixes, upgrades? I'd look it up in he WSM's but it might take me the rest of the day to find it!!!
Nordschleife Master
Joined: Dec 2004
Posts: 6,164
Likes: 7
From: Guelph, Ontario, Canada
Chris,
yes it will, Intitially it will be a replacement but I will offer an advanced one that will provide 'current' technology that will be more automatic. I will put up some CAD pictures as soon as I get this renlist thing figured out.
yes it will, Intitially it will be a replacement but I will offer an advanced one that will provide 'current' technology that will be more automatic. I will put up some CAD pictures as soon as I get this renlist thing figured out.