Poll

Are you interested in a high quality, reliable, modern day, microcontroller based replacement for the auto climate control system?

Of course! I hate sweating in the summer and/or freezing in the winter.
14 (56%)
Where was this when I spent 2 grand to replace my crappy system with the same crap?
1 (4%)
No way, I love the eccentricities of my Benz and would never replce anything with non MB parts even though I do have to wear electric socks to drive during the winter.
1 (4%)
HA HA. You poor US saps. I live in Europe, South Africa, Australia and could care less. :)
9 (36%)

Total Members Voted: 23

Author Topic: ACCII Automatic climate control replacement.  (Read 7760 times)

zeppelinboy

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ACCII Automatic climate control replacement.
« on: 24 September 2007, 04:04 PM »


I hate the ACCII system and think it is purely evil (even more evil than Bosch kjet fuel injection). I have spent the last several weeks developing a microcontroller based replacement for the servo valve and amplifier. If there is enough interest, I will start supplying these to the community. It will be priced under $500. It retains all of the original functions of the system and uses the original controls. On the outside, you will see nothing different, but on the inside the amplifier and servo are replaced with modern day solid state electronics. Installation is no more complicated than installing a car stereo, plus removal and replacement of the servo valve (a few hose clamps).

Justin
79 450SEL "Der Kommisar"
81 Datsun 280ZX 2+2
83 Chevy S-10 Blazer - D44 SAS + 12 inches o lift
96 Chevy S-10 w/LT1 inside

oscar

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Re: ACCII Automatic climate control replacement.
« Reply #1 on: 24 September 2007, 05:07 PM »
With the choices available I had to vote in the last category but that's not to say I could care less ;)  This sounds like a great mod zep.  Good luck with it and I hope you get plenty of interest.  'scuse the questions but curiosity has got the better of me.

Is your servo built entirely from scratch ie housing and innards?   I assume you've got a working version on Der Kommisar, how's it performing?
1973 350SE, my first & fave

zeppelinboy

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Re: ACCII Automatic climate control replacement.
« Reply #2 on: 24 September 2007, 05:45 PM »
Oscar,

Thanks for the interest.

Without going into too much detail, the ACCII servo has three main functions:

1. It controls the heater water flow, on or off.
2. It sets the fan speed to one of 6 different levels.
3. It sets the flap positions by controlling vacuum routing and vacuum solenoids.

It makes these decisions based upon the position of the selector switch (auot hi or low, bilev, and defrost), the temperature set wheel, and the cabin and outside air temp. The servo is controlled via these inputs as well as the climate control amplifier which is basically an analogue comparator circuit. The servo mechanically switches electrical and vacuum circuits via a rotary type switch.

My solution replaces the servo with a standard heater valve. As inputs it uses the selector switch, thumbwheel temperature set, in cabin temp and supply air temp. The mercedes thermistors are replaced with solid state temp sensors. The mercedes amplifier is replaced by my module which controls the heater valve,  fan speed (continuously variable from full off to full on, and flap positions.

My module is based upon a modern microcontroller and associated circuitry and controls all of the functions of the system electronically. The module is located in the car where the amplifier used to be. The only thing located under the hood and subjected to the harsh environment is the heater valve itself.

The version that I have in Der Kommisar is functioning beautifully. I cannot compare it to a brand new ACCII system as I have never come across a working one. However, since I based the operation of my design off of the mercedes manual for the function of  the ACCII system, it should perform exactly the same, only more reliably. I made only a few changes in the operation:

1. The fan has continuously variable speed in my system, in the mercedes system it has 6 steps.
2. In my system if the in cabin temp is very cold and the supply air is sufficiently warm in heating mode, then the center flaps will open. In the mercedes system, the center vents never open for heater mode.
3. In my system if in cooling mode and the supply air temp is higher than the set temp, then the center flaps will close, thus preventing you from being blasted in the face with hot air.


I really just did this for me since I was unhappy with the ACCII system. However, I have realized that many others have problems with this system and I would be happy to provide them with an alternative solution.


Justin

79 450SEL "Der Kommisar"
81 Datsun 280ZX 2+2
83 Chevy S-10 Blazer - D44 SAS + 12 inches o lift
96 Chevy S-10 w/LT1 inside

oscar

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Re: ACCII Automatic climate control replacement.
« Reply #3 on: 24 September 2007, 06:23 PM »
Thanks Justin, that's fantastic 8)
1973 350SE, my first & fave

Papalangi

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Re: ACCII Automatic climate control replacement.
« Reply #4 on: 24 September 2007, 07:44 PM »
I'd go for and even be willing to be a beta tester.  I assume you will be using a stamp or pic microcontroller.

Just be careful about any patent rights http://unwiredtools.com/accii.html?src=mercedesshop may have.  Hate to see you get shot down.

Michael
1976 450SEL, 116.033  Sold it to buy a '97 Crown Vic.  Made sense at the time.
1971 250C, 114.023      Sad but true, it's gone to a new home.
1976 280C  Stolen by the City of Seattle, sort of.
1970 250/8, traded in on a 1993 Land Rover Disco

zeppelinboy

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Re: ACCII Automatic climate control replacement.
« Reply #5 on: 24 September 2007, 11:49 PM »
Michael,

Thanks for the link.

Their system seems pretty similar to mine. The only patent that I would be really worried about is the original patent for the ACCII system, but since it was introduced in 71 on the Chrysler imperial I am sure that the patent has long since expired. The only thing patentable in my system is the actual I.P. inside the pic microcontroller.  They use the word proprietary when referring to their "controller module" which implies that it is not patented. Unless they are selling these things for some crazy sum, it would not be worth the expense to attempt to patent it as the market has to be fairly small.

I am not trying to start a business here, but offer folks the opportunity to take advantage of the work that I put into designing this replacement. One of the main reasons that I want to gauge interest is to determine if I should get a small run of circuit boards printed, or if I should just make them one at a time if people are want one.

BTW, I would be happy to make you up a system. Is your ACCII system currently non functioning?

Justin
79 450SEL "Der Kommisar"
81 Datsun 280ZX 2+2
83 Chevy S-10 Blazer - D44 SAS + 12 inches o lift
96 Chevy S-10 w/LT1 inside

koan

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Re: ACCII Automatic climate control replacement.
« Reply #6 on: 25 September 2007, 05:09 AM »

....even more evil than Bosch kjet fuel injection.


Not seen the automatic climate control system in the flesh, only in pictures but I have the vacuum diagram in the A/C book, I can't believe the amount of plumbing and actuators it uses. Appearance wise the center console controls look like something hacked together from a Dick Smith shop (hobby electronics).

K-Jetronic on the other hand is elegant simplicity, a purely mechanical masterpiece.

Good luck with your project.

koan
Boogity, Boogity, Boogity, Amen!

mabryt

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Re: ACCII Automatic climate control replacement.
« Reply #7 on: 25 September 2007, 10:06 AM »
Guten tag Zeppelinboy!

First, thanks for the info on my other thread. 

Second, I am definitely interested in your mod, with two provisos: a) the exact cost (I've been spoiling her lately with new tires, master cylinder, fuel pump, ignition coil, wires, plugs, etc.) and b) how many hours are required for the install.

Meanwhile, when you wrote before that it's possible to "bypass" the heater core, does that mean just clamping the hose that currently leads from the servo?

Thanks- TJM<
1977 280SE - Silver Green

Papalangi

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Re: ACCII Automatic climate control replacement.
« Reply #8 on: 25 September 2007, 10:38 AM »

BTW, I would be happy to make you up a system. Is your ACCII system currently non functioning?

Justin

Mine is more of a MCCII system.  I get out, open the hood and adjust the ball valve.  Fan speed is set by poking the buttons till air comes out.

The cabin temp sensor is missing and the servo wasn't working so I had Ben, the PO, put in the ball valve while I was flying down to Dallas to pick up the car for the drive back to Seattle.

I've played with Basic Stamps, use and program PLCs almost daily, and love to tinker so would love to switch it over to a digital system.  Unwired tools system is around $700, comes with everything you need and has had several versions.

For those not in the know, the ACCII system was licensed from Chrysler.  It was used it the 71-74 Imperial.  Notice the MB didn't learn from Chrysler but went ahead with a system that was discontinued by the outfit that came up with it.

http://www.imperialclub.com/Repair/Lit/Master/281/cover.htm

Michael
1976 450SEL, 116.033  Sold it to buy a '97 Crown Vic.  Made sense at the time.
1971 250C, 114.023      Sad but true, it's gone to a new home.
1976 280C  Stolen by the City of Seattle, sort of.
1970 250/8, traded in on a 1993 Land Rover Disco

CraigS

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Re: ACCII Automatic climate control replacement.
« Reply #9 on: 25 September 2007, 10:47 AM »
They also used the Bendix Treadle Vac system for brakes on my 300b - another system that was used on US vehicles such as Cadillac, and that wasn't any good either !




For those not in the know, the ACCII system was licensed from Chrysler.  It was used it the 71-74 Imperial.  Notice the MB didn't learn from Chrysler but went ahead with a system that was discontinued by the outfit that came up with it.

http://www.imperialclub.com/Repair/Lit/Master/281/cover.htm

Michael


Papalangi

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Re: ACCII Automatic climate control replacement.
« Reply #10 on: 25 September 2007, 02:17 PM »
I like the feature set you have come up with.  The only addition I would add is a fail safe full fan speed if the defrost button is pushed and the system is down.

When can I get mine?

Let's talk price, I can come up with wiring, hoses and such and am quite handy with a soldering iron if a kit form is doable.

Michael
1976 450SEL, 116.033  Sold it to buy a '97 Crown Vic.  Made sense at the time.
1971 250C, 114.023      Sad but true, it's gone to a new home.
1976 280C  Stolen by the City of Seattle, sort of.
1970 250/8, traded in on a 1993 Land Rover Disco

zeppelinboy

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Re: ACCII Automatic climate control replacement.
« Reply #11 on: 25 September 2007, 04:46 PM »
Wow!

I didn't expect to be selling units already. :)
Realistically, 2 - 4 weeks before I could get something out.
I would need a few days to firm up the pricing, but here are my best guestimates.

Option #1 - fully assembled kit - you will still need to install it and it will require wiring into the electrical system much like installing a car stereo (I am currently evaluating the most feasible way so that as few electrical splices as possible will be required. Price - no more than $400.

Option #2 - unassembled kit - all components required for functioning - however, the circuit board will need to be assembled (you will be provided with all of the circuit board materials). you will need to provide an enclosure and mounting for the controller as well as various and sundry wiring. Price - no more than $250.

The thing about option 2 is that if you assemble it, you will also need a way to test the function of the module, I can test modules that I make myself, but I can only test the function of the microcontroller in the unassembled kit.

Installation time will depend upon your level of skill and familiarity with your vehicle. I could easily do it in less than an hour, but an extreme novice could take 4 or more hours.

Installation will involve:

1. Removing glove compartment liner, lower trim panel on passenger side, and a/c control panel.
2. Making the necessary electrical connections ~15
3. Rerouting vacuum lines (ideally you will test the function of the vacuum system here, which could run into a major time consumer as problems can be a real pain to run down) (vac lines are necessary as the flaps use vac to operate).
4. Mount module.
5. Place temp sensors.
6. Remove servo and replace with heater valve.


The most time consuming step is #2. This takes me about 20 minutes as I solder and heat shrink all of my my electrical connections. If one was to use splice style connectors, this step may be shortened.

I will firm things up soon.

Justin
79 450SEL "Der Kommisar"
81 Datsun 280ZX 2+2
83 Chevy S-10 Blazer - D44 SAS + 12 inches o lift
96 Chevy S-10 w/LT1 inside

zeppelinboy

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Re: ACCII Automatic climate control replacement.
« Reply #12 on: 25 September 2007, 04:53 PM »
Replies to other questions:

T - In order to bypass the heater core, you could just pinch off the hose somehow, but this probably wouldn't be very reliable. The best way is to disconnect the two heater hoses that run from the servo to the heater core and hook them together and then disconnect the two hoses that run from the engine block to the servo and heater pump and connect them together. You will also want to remove the electrical connector from the heating water pump if you do this as it will be out of the loop now. Heater hose spicers can be found at any auto store as well as walmart etc.


Pap - My system retains the "fail safe" defrost mode.

Justin
79 450SEL "Der Kommisar"
81 Datsun 280ZX 2+2
83 Chevy S-10 Blazer - D44 SAS + 12 inches o lift
96 Chevy S-10 w/LT1 inside

Papalangi

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Re: ACCII Automatic climate control replacement.
« Reply #13 on: 26 September 2007, 12:13 PM »
Sounds good, it will take me 2 - 4 weeks to free up some play money.

If you have used surface mount components, I'll leave the soldering to you.  In fact, I may leave assembly to you so you can test it for me.

Let us know when you are ready to go into production.

Michael
1976 450SEL, 116.033  Sold it to buy a '97 Crown Vic.  Made sense at the time.
1971 250C, 114.023      Sad but true, it's gone to a new home.
1976 280C  Stolen by the City of Seattle, sort of.
1970 250/8, traded in on a 1993 Land Rover Disco

mabryt

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Re: ACCII Automatic climate control replacement.
« Reply #14 on: 26 September 2007, 02:42 PM »
Hey there-

Thanks very much for the info.  I'm definitely interested in Option #1, but I worry about tracking down leaks in the vac lines.  I'm happy to mess with pretty much everything else on the car, except those!  So instructions need to be idiot proof !
1977 280SE - Silver Green