AC system question
03-01-2008, 08:48 PM
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AC system question
I am in the process of replacing my AC controler and going with an automated ac system like on some new cars.
My question is geared towards an 89 model.
I see that the heater valve is still controled numatically but when I removed the dash and examined the ac evaperator/blower box I can't figure out whether the rest of the valves are electric or numatic and to be honest the schematic is a little confusing "so much stuff" to make cold air.
Reason I ask is I can get relays to control the valves if there electrical but if they are all numatic it just adds one more obstical to overcome.
89 928 5 speed, major project
My question is geared towards an 89 model.
I see that the heater valve is still controled numatically but when I removed the dash and examined the ac evaperator/blower box I can't figure out whether the rest of the valves are electric or numatic and to be honest the schematic is a little confusing "so much stuff" to make cold air.
Reason I ask is I can get relays to control the valves if there electrical but if they are all numatic it just adds one more obstical to overcome.
89 928 5 speed, major project
03-01-2008, 09:37 PM
#2
Chronic Tool Dropper
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The various air flaps and the heater control valve are vacuum operated, and controlled by solenoid valves that live in a group forward (forward is closer to the front of the car) of and slightly below the dash controller. The solenoid for that heater valve is fail-open, as is the valve itself, so the system defaults to hot until power and vacuum are applied to the valve.
The system manages five solenoids to control the defrost flap, the footwell flap, the center vent comb flap, the fresh-air flap, and that heater control flap. The blend door is actuated by an electric servo-motor that looks at inside temp, outside temp and the temp sensor on the controller slider. It also controls the fresh air flap and heater valve in concert with the airflow selector on the controller.
The AC system in my '89 is automated as far as temp control and basic outside vs inside source airflow are concerned. I still manually select air outlets and fan speed. Is your plan to automate those two remaininig functions?
The system manages five solenoids to control the defrost flap, the footwell flap, the center vent comb flap, the fresh-air flap, and that heater control flap. The blend door is actuated by an electric servo-motor that looks at inside temp, outside temp and the temp sensor on the controller slider. It also controls the fresh air flap and heater valve in concert with the airflow selector on the controller.
The AC system in my '89 is automated as far as temp control and basic outside vs inside source airflow are concerned. I still manually select air outlets and fan speed. Is your plan to automate those two remaininig functions?
03-01-2008, 09:40 PM
#3
Under the Lift
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All the actuators are all pneumatic (vacuum), although the vacuum ports that control them are controlled by electrical solenoids, as the controller switches are electrical. The temperture control is automatic. What else were you planning to automate?
03-01-2008, 10:10 PM
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I wouldn't recommend you continue with this plan... It is much more complicated than you may think to change it and its already an automatic climate control system. The only things not already automated are fan speed..
Alan
Alan
03-01-2008, 10:14 PM
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Thanks for the info! Actually I never even thought that the valves where controled by electric solenoid valves but it makes sence cosidering the AC controller has no numatic lines going to it.
I am putting a Windows XP computer "micro atx board" in the car.
And I wanted to remove all the components in the center console and hook them up to it.
The radio will be part of a program contolled by a sound card on the computer that I saw on the web thats seems pretty neet.
Then there is GPS, built in cell phone and blue tooth, WIFI and brodband internet for trafic updates and access if I needed to but probably never will, and then there is a program that I can link to the engine "I think".
And I wanted to incorporate the ac system into it. also have auto lights when it gets dark and speed up the wipers when there is more water on the windshield"not entirly sure how I will do that".
But all the stuff is there on the web if your willing to research and like doing this kind of stuff.
The weight will be minimal as with the elecrical consumption.
The touch screen will be kinda neet and the fact that I totaly installed it myself will be fun.
But now that gave that info, the ac system will be alot easier.
Now for the lights and wipers.
89 928 5 speed, major project
I am putting a Windows XP computer "micro atx board" in the car.
And I wanted to remove all the components in the center console and hook them up to it.
The radio will be part of a program contolled by a sound card on the computer that I saw on the web thats seems pretty neet.
Then there is GPS, built in cell phone and blue tooth, WIFI and brodband internet for trafic updates and access if I needed to but probably never will, and then there is a program that I can link to the engine "I think".
And I wanted to incorporate the ac system into it. also have auto lights when it gets dark and speed up the wipers when there is more water on the windshield"not entirly sure how I will do that".
But all the stuff is there on the web if your willing to research and like doing this kind of stuff.
The weight will be minimal as with the elecrical consumption.
The touch screen will be kinda neet and the fact that I totaly installed it myself will be fun.
But now that gave that info, the ac system will be alot easier.
Now for the lights and wipers.
89 928 5 speed, major project
03-01-2008, 10:22 PM
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Make sure you understand what you are trying to do before you sacrifice the car... many people have desired to do similar - none to date have really executed on it... It is way hard to even figure out how the stock systems work... let alone improve on them in any way...
I would never trust anything on my car that I needed to have work reliably to anything run by windows - for sure not the lighting...!
I think you may be dreaming a bit ....
Alan
I would never trust anything on my car that I needed to have work reliably to anything run by windows - for sure not the lighting...!
I think you may be dreaming a bit ....
Alan
03-01-2008, 11:05 PM
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I gave up thinking about it once I saw Alan thought it would be a bad idea to go there. He seems to understand the electrics on the 928 better than anyone and isn't afraid to suggest changes to them but when he said it isn't worth going down that road I decided to leave the AC controls off my list.
After thinking about it I realized the only thing about the AC controls I didn't like was the actual control head appearance, the way it functions is fine, the way it looks is just kind of old and looks like it belongs in a 1978 Chevrolet Impala but unfortunately to remove that head and put something in its place is way too big of a project behind the dash to justify merely changing the appearance of a few square inches of the console.
After thinking about it I realized the only thing about the AC controls I didn't like was the actual control head appearance, the way it functions is fine, the way it looks is just kind of old and looks like it belongs in a 1978 Chevrolet Impala but unfortunately to remove that head and put something in its place is way too big of a project behind the dash to justify merely changing the appearance of a few square inches of the console.
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03-01-2008, 11:29 PM
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Hi RayFinkel--
In my spare time I teach computers how to run power plants. I'm continually amused by clients who want to use PC's, specifically Windows PC's, as a basic building block for critical controls. For the car stuff, it's fine to use a PC screen to control a radio or show movies to the kids or give directions. It's probably OK to integrate HVAC controls too, provided you keep in mind some of the failure-mode requirements. Those are answered by the basic questions that start with "What do you want the xxx device to do when the computer fails?" You get to answer that question for every device you want to control. Since there's no good answer for things like the wipers, perhaps you can use something other than your PC for the basic control, and use the PC for non-basic functions in parallel with the existing controls. For instance, leave the wiper lever there and functioning, but add the rain- and speed-sensing interval control you mention. Auto lights? Ummm, sure, so long as there's a hardware on and off solution that will work no matter what the computer mode. That might be a simple toggle switch hidden someplace to swap control from the current pod switch to the computer.
Keep in mind that most common PC components are not rated for anything close to the levels of thermal and mechanical abuse that are common in a car. Simple stuff like floppy drives, not withstanding hard drives or DVD-ROM needed to boot a PC. I guess you could teach it to start and run on a stick with no moving parts, right? USB connector isn't rated for the vibration though. Getting the idea?
I preach and teach industrial automation, real automation that requires virtually no human intervention. I would have no problem adapting some industrial-strength controllers to manage many functions on the car that currently require driver intervention. I would NEVER depend on a PC platform to real-time control any core systems in my car. JMHO, of course.
In my spare time I teach computers how to run power plants. I'm continually amused by clients who want to use PC's, specifically Windows PC's, as a basic building block for critical controls. For the car stuff, it's fine to use a PC screen to control a radio or show movies to the kids or give directions. It's probably OK to integrate HVAC controls too, provided you keep in mind some of the failure-mode requirements. Those are answered by the basic questions that start with "What do you want the xxx device to do when the computer fails?" You get to answer that question for every device you want to control. Since there's no good answer for things like the wipers, perhaps you can use something other than your PC for the basic control, and use the PC for non-basic functions in parallel with the existing controls. For instance, leave the wiper lever there and functioning, but add the rain- and speed-sensing interval control you mention. Auto lights? Ummm, sure, so long as there's a hardware on and off solution that will work no matter what the computer mode. That might be a simple toggle switch hidden someplace to swap control from the current pod switch to the computer.
Keep in mind that most common PC components are not rated for anything close to the levels of thermal and mechanical abuse that are common in a car. Simple stuff like floppy drives, not withstanding hard drives or DVD-ROM needed to boot a PC. I guess you could teach it to start and run on a stick with no moving parts, right? USB connector isn't rated for the vibration though. Getting the idea?
I preach and teach industrial automation, real automation that requires virtually no human intervention. I would have no problem adapting some industrial-strength controllers to manage many functions on the car that currently require driver intervention. I would NEVER depend on a PC platform to real-time control any core systems in my car. JMHO, of course.
03-01-2008, 11:45 PM
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Go for it! Damn the nay sayers!
We wouldn't have innovation if none of us tried different things. I would suggest you stay away from the engine control though.
www.mp3car.com is a pretty good starter sight. Those guys still think windows, but think mandrake
PM for more if your really into this thought.
I built a system for the boat - ran the nav, auto pilot, electrical, A/C, refrigeration, etc....
Of interesting note - We use it with our Fire/EMS and currently use the idea on the Rescues to control the whole rig - it does work! The biggest problem is operator error
We wouldn't have innovation if none of us tried different things. I would suggest you stay away from the engine control though.
www.mp3car.com is a pretty good starter sight. Those guys still think windows, but think mandrake
PM for more if your really into this thought.
I built a system for the boat - ran the nav, auto pilot, electrical, A/C, refrigeration, etc....
Of interesting note - We use it with our Fire/EMS and currently use the idea on the Rescues to control the whole rig - it does work! The biggest problem is operator error
03-02-2008, 06:37 PM
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Thanks for all the info.
I know you are all looking out for my Or the 928's best interest,lol, but this car is my hobby.
The info on the solenoids was perfect.
To be honest I was never impressed with the porsche's wiring after,at 17 years old, purchasing a beautiful 77 928. That thing broke down on the side of the road so many times. But I loved it and now I have an 89 to make it into the perfect car. Part porsche part me!
89 928 5 speed, major project
I know you are all looking out for my Or the 928's best interest,lol, but this car is my hobby.
The info on the solenoids was perfect.
To be honest I was never impressed with the porsche's wiring after,at 17 years old, purchasing a beautiful 77 928. That thing broke down on the side of the road so many times. But I loved it and now I have an 89 to make it into the perfect car. Part porsche part me!
89 928 5 speed, major project
03-02-2008, 09:13 PM
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Rayfinkel--
As you continue your research into the HVAC workings, keep in mind that the control head isn't where the smarts are in the system. I handles the driver input on target temp, the fan speed selection, and the airflow selection for defrost and footwell. Smart stuff is in the controller at the temp setting motor.
Have fun, and be sure to update us on your progress!
As you continue your research into the HVAC workings, keep in mind that the control head isn't where the smarts are in the system. I handles the driver input on target temp, the fan speed selection, and the airflow selection for defrost and footwell. Smart stuff is in the controller at the temp setting motor.
Have fun, and be sure to update us on your progress!
04-07-2008, 07:12 AM
#12
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The various air flaps and the heater control valve are vacuum operated, and controlled by solenoid valves that live in a group forward (forward is closer to the front of the car) of and slightly below the dash controller. The solenoid for that heater valve is fail-open, as is the valve itself, so the system defaults to hot until power and vacuum are applied to the valve.
The system manages five solenoids to control the defrost flap, the footwell flap, the center vent comb flap, the fresh-air flap, and that heater control flap. The blend door is actuated by an electric servo-motor that looks at inside temp, outside temp and the temp sensor on the controller slider. It also controls the fresh air flap and heater valve in concert with the airflow selector on the controller.
The AC system in my '89 is automated as far as temp control and basic outside vs inside source airflow are concerned. I still manually select air outlets and fan speed. Is your plan to automate those two remaininig functions?
The system manages five solenoids to control the defrost flap, the footwell flap, the center vent comb flap, the fresh-air flap, and that heater control flap. The blend door is actuated by an electric servo-motor that looks at inside temp, outside temp and the temp sensor on the controller slider. It also controls the fresh air flap and heater valve in concert with the airflow selector on the controller.
The AC system in my '89 is automated as far as temp control and basic outside vs inside source airflow are concerned. I still manually select air outlets and fan speed. Is your plan to automate those two remaininig functions?
Dr Bob
Would this explain why I have constant heat coming from defrost???
What is first step to fix??
