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  #1  
Old 07-21-2013, 07:55 PM
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1980 123 acc has only defrost function

Looks like someone put an aftermarket radio and got the vacuum lines crossed,any one have a diagram or pic?I don't know if that e
ffects control panel function

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  #2  
Old 07-21-2013, 08:01 PM
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Defrost-only working is the 'fail-safe" default on that system, meaning that some major part is not working. It isn't likely that a vacuum fault alone is responsible.

You need to read up on the ACC II system. Start by searching "evil servo" and go from there.

Also check out the links I posted in this thread:
http://www.peachparts.com/shopforum/diesel-discussion/327465-1980-300sd-servo-bypass-amp-question.html
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2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

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  #3  
Old 07-21-2013, 08:02 PM
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First check the green vac line under the hood. That's the main supply for the ACC.
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  #4  
Old 07-21-2013, 08:04 PM
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I highly doubt that is your issue, you have the evil servo system....the most hated climate control system know to man.....read this manual to understand how it works. If your interested in getting it working again, I can guide you, but be prepared it may end up costing you 500-700$

1971 Chrysler Imperial Auto-Temp 2 Service Reference Guide - Session 281
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  #5  
Old 07-22-2013, 01:32 PM
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Some free advice you can take or leave: unless you are a really, really fast learner, you want to take up cooljjay on his offer....

Expertise on this system is thin on the ground everywhere now, it's an old and unloved thing, fancy-dancy for the early 1970s when it was designed, but a certifed PITA nearly 35+ years on. So when someone offers to walk you through, I wouldn't look the gift horse in the mouth too long .
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2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22
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  #6  
Old 07-22-2013, 02:19 PM
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The ACC II is a highly misunderstood system. Most problems are actually quite simple and the servo/amplifier is frequently blamed before any other tests are performed.

Check fuses 2, 3 & 10. Also check your yellow/green vacuum (supply) line and the 4 way rubber connections near the brake booster. Check the nylon lines at the servo as they can sometimes crack in the bend near the connectors.

#1 cause of "failed servos" is a shorted A/C low pressrue switch which will blow the ACC fuses when the compressor switch is thrown.

here is the ACCII W123 specific manual:

http://www.w123.it/file/W116climatecontrol%20manual.pdf
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Did you just pass my 740 at 200 kmh in a 300SD?????

1978 300SD 'Phil' - 1,315,853 Miles And Counting - 1, 317,885 as of 12/27/2012 - 1,333,000 as of 05/10/2013, 1,337,850 as of July 15, 2013, 1,339,000 as of August 13, 2013



100,000 miles since June 2005 Overhaul - Sold January 25th, 2014 After 1,344,246 Miles & 20 Years of Ownership
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  #7  
Old 07-22-2013, 02:25 PM
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Quote:
Originally Posted by Zacharias View Post
Defrost-only working is the 'fail-safe" default on that system, meaning that some major part is not working. It isn't likely that a vacuum fault alone is responsible.

You need to read up on the ACC II system. Start by searching "evil servo" and go from there.
When you experience a 'hunting' ACCII system, one that switches back and forth between center vent/defrost or A/C and Heat, pull the amplifier (behind glovebox) and repair the solder joints on the thermistors on the circuit board.

This is a very common, 20 minute fix, exactly the same as the broken solder joints on the tach amps.

I can get a replacement ACC II amplifier for less than $100.00...
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Did you just pass my 740 at 200 kmh in a 300SD?????

1978 300SD 'Phil' - 1,315,853 Miles And Counting - 1, 317,885 as of 12/27/2012 - 1,333,000 as of 05/10/2013, 1,337,850 as of July 15, 2013, 1,339,000 as of August 13, 2013



100,000 miles since June 2005 Overhaul - Sold January 25th, 2014 After 1,344,246 Miles & 20 Years of Ownership
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  #8  
Old 07-22-2013, 02:32 PM
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Quote:
Originally Posted by textech56 View Post
Looks like someone put an aftermarket radio and got the vacuum lines crossed,any one have a diagram or pic?I don't know if that effects control panel function
It's in the link....
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Did you just pass my 740 at 200 kmh in a 300SD?????

1978 300SD 'Phil' - 1,315,853 Miles And Counting - 1, 317,885 as of 12/27/2012 - 1,333,000 as of 05/10/2013, 1,337,850 as of July 15, 2013, 1,339,000 as of August 13, 2013



100,000 miles since June 2005 Overhaul - Sold January 25th, 2014 After 1,344,246 Miles & 20 Years of Ownership
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  #9  
Old 07-22-2013, 02:44 PM
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Quote:
Originally Posted by Zacharias View Post
Defrost-only working is the 'fail-safe" default on that system, meaning that some major part is not working. It isn't likely that a vacuum fault alone is responsible.
On the ACCII system, Everything is based on vacuum, including when the A/C compressor doesn't engage and when none of the buttons on the panel recat when pushed. about vacuum.

ANY vacuum loss whatsoever and the system won't come on in any mode but defrost.

You need a vacuum gauge and the diagram posted in the link above to check for vacuum leaks.

Email me via my profile if you need tech support. I've been driving a 300SD with ACC II for over 20 years....
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Did you just pass my 740 at 200 kmh in a 300SD?????

1978 300SD 'Phil' - 1,315,853 Miles And Counting - 1, 317,885 as of 12/27/2012 - 1,333,000 as of 05/10/2013, 1,337,850 as of July 15, 2013, 1,339,000 as of August 13, 2013



100,000 miles since June 2005 Overhaul - Sold January 25th, 2014 After 1,344,246 Miles & 20 Years of Ownership
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  #10  
Old 07-22-2013, 03:03 PM
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Quote:
Originally Posted by Doktor Bert View Post
#1 cause of "failed servos" is a shorted A/C low pressrue switch which will blow the ACC fuses when the compressor switch is thrown.
Wrong! The number one cause of a failed acc II system, is a frozen aux water pump. The pump freezes and then it blows the amplifier behind the glove box liner.

The number two reason for the acc II not working correctly is the temp sensor tube that runs from the passenger side speaker grille to the blower assembly, with out this tube...the system cannot sample the cabin air.
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  #11  
Old 07-22-2013, 03:16 PM
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Quote:
Originally Posted by cooljjay View Post
Wrong! The number one cause of a failed acc II system, is a frozen aux water pump. The pump freezes and then it blows the amplifier behind the glove box liner.

The number two reason for the acc II not working correctly is the temp sensor tube that runs from the passenger side speaker grille to the blower assembly, with out this tube...the system cannot sample the cabin air.
The causes you listed are indeed issues with the system. The sensor tube (which can be replaced with hardware store water pipe insulation) will only cause the system to 'hunt' or switch between high and low blower speeds and/or A/C heat.

All the later model cars had an external fuse added to prevent a water pump failure from damaging anything. It is fuse #12 in the W123 ACC-II diagram.

However, the most prominent complaint I have experienced in 20 years of working on these systems is blown ACC fuses when the compressor switch is thrown, which everyone always blames on the servo.

Keep in mind the A/C compressor cut-out switch is power controlled and not ground controlled, hence a short will blow the fuses and seem like a bad servo.

I am the guy who fixed these systems when everyone else gave up on them...FWIW
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Did you just pass my 740 at 200 kmh in a 300SD?????

1978 300SD 'Phil' - 1,315,853 Miles And Counting - 1, 317,885 as of 12/27/2012 - 1,333,000 as of 05/10/2013, 1,337,850 as of July 15, 2013, 1,339,000 as of August 13, 2013



100,000 miles since June 2005 Overhaul - Sold January 25th, 2014 After 1,344,246 Miles & 20 Years of Ownership
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  #12  
Old 07-23-2013, 12:26 AM
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Quote:
Originally Posted by cooljjay View Post
I highly doubt that is your issue, you have the evil servo system....the most hated climate control system know to man.....read this manual to understand how it works. If your interested in getting it working again, I can guide you, but be prepared it may end up costing you 500-700$

1971 Chrysler Imperial Auto-Temp 2 Service Reference Guide - Session 281
AWESOME MANUAL !!

good info for study !! beginning immediately......
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  #13  
Old 07-23-2013, 01:04 AM
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Quote:
Originally Posted by BenzDieselTuner View Post
AWESOME MANUAL !!

good info for study !! beginning immediately......
Get reading, they be a test a noon tomorrow
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  #14  
Old 08-18-2013, 01:09 AM
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Finally found EVIL SERVO thread. So after looking at a few bad old cars ( that 300D , BMW 63..., Saab convertibles..) I am back to square ONE - and strongly considering making the 6.5 hour trip north for the white 78 300CD.

If I get this car aside from any other fixes it may need if I have EVIL SERVO issues I'll be back....



...

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