Author Topic: ACC is working! Sort of...  (Read 6066 times)

1980sdga

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ACC is working! Sort of...
« on: 12 May 2011, 06:00 PM »
I went through and checked all the circuits with a mity vac.  I pulled vacuum through the push button vacuum connector, and then chased the circuits down from there.  I finally found that the recirc. "double pot" in the passenger footwell was shot as were most of the hoses inside the ACC servo.  I replaced the lines in the servo, greased the servo vacuum disc, replaced all the one way check valves and all seems well  :D  I plugged both the lines on the recirc pot and am looking for another.

During testing the low pressure switch started cutting in (Probably because it hasn't been charged in years. It does blow cold though I just don't want to run it low on refrigerant.) so I can't do a complete function test until I address that   :-[

The amp and servo function appears OK and the heat valve seems to function. (still need to address the aux. pump switching)

I actually tested it with a ziploc bag full of ice and a hot wet rag in another bag.  I can hold them over the sniffer and the system switches from hot to cold and back. 

Thanks a lot Joe and Raptelan! 
Jon


Little by little I have grown fond of the infamous Auto Temp II we have in our 116's

jbrasile

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Re: ACC is working! Sort of...
« Reply #1 on: 12 May 2011, 08:48 PM »
1980sdga, that is great news!! Amazing how vacuum leaks seem to plague these fresh air door actuators.

Actually unless you wish to have the fresh air function operational, you may leave the hoses plugged and avoid the expense of replacing the actuator. That will leave you with recirculating air all the time but it helps increase the efficiency of the a/c by not allowing external air in. As I mentioned before, the system automatically closes 80% of the outside air when max cooling is needed but it will open to full fresh air as soon as it "thinks" its appropriate.

I have this mod on my 78 450SEL and it works well.

You should probably have the a/c serviced by a professional before bringing it back to regular use. Change the receiver drier and have the shop do a system oil change and re-charge. If  R-12 is still available in your area, spend the extra cash and get it re-charged with freon after making sure there are no leaks.

Tks,

Joe


1980sdga

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Re: ACC is working! Sort of...
« Reply #2 on: 13 May 2011, 05:24 AM »
I plan on having a AC shop charge the system.  I've done it myself before but I think the system needs a going over and the proper amount of oil/refrigerant installed.  I didn't even think about changing the drier. I'll have to round one up before taking it in.

My system was changed to 134a and even has an official looking tag under the hood!  I'm not sure if they changed out the expansion valve (Or if it's necessary) but it seemed to cool well when I got the car.

I have both vacuum lines to the fresh air pot plugged for now but if I can find a new part I'll probably change it.

Thanks again for the help!   I'm going out of town for a couple of days and If the system still functions when I get home I'm gonna button it up.
Jon


Little by little I have grown fond of the infamous Auto Temp II we have in our 116's

Casey

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Re: ACC is working! Sort of...
« Reply #3 on: 13 May 2011, 05:28 AM »
I dunno why you're thanking me - I am comparably stupid with this crap.  If you have some extra time, feel free to drive up to MD and work on getting mine working!

BWalker82

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Re: ACC is working! Sort of...
« Reply #4 on: 13 May 2011, 05:34 AM »
I'm impressed your AC works... I have not the slightest clue where to even start diagnostics on mine.  Mine likes to blow heat, regardless of the temp setting out of all but the two center vents, with a puff of cool air every now and then just to tease you.

Have you converted yours to 134a?

-BW
-BW

Casey

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Re: ACC is working! Sort of...
« Reply #5 on: 13 May 2011, 05:46 AM »
I'm impressed your AC works... I have not the slightest clue where to even start diagnostics on mine.  Mine likes to blow heat, regardless of the temp setting out of all but the two center vents, with a puff of cool air every now and then just to tease you.

This is *EXACTLY* what mine does!  I don't have any blower motor either - do you?  Doesn't matter what ACC button I press.  On mine heat just drifts in as I drive.  I keep the vents shut which works pretty well.

1980sdga

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Re: ACC is working! Sort of...
« Reply #6 on: 13 May 2011, 06:32 AM »
Well Raptelan, you asked a question that Joe answered which helped me piece the puzzle together  ;D

It is a super complicated system so like Joe said, don't go fooling with too many vacuum lines!  It's easy to get too many connections un hooked and lose your way  :o

The biggest problems I found were the vacuum hoses under the lid of the servo.  They looked OK but were really swollen and leaking badly.  I carefully replaced all of them with new hoses and things started working again  :D  There is also a "Disc valve" :



which the servo turns. I believe it changes the flaps and turns the center vents "OFF" when the system is heating.  If this disc is leaking the whole system is FUBAR.  Thankfully it's easy to get too.  My "disc" was leaking as well...

Before you can address any of this you need to make sure your amp and servo are working though...  You should hear the servo working when the ignition is on and the thumbwheel is turned.  Thankfully, this part of the system will work without vacuum.

If your servo is silent. (It should also "Park" itself after the ignition is turned off.  You should hear it running for about 10 seconds after the ignition key is off/removed.) then I guess it's time to chase fuses.  I got lucky with this part... I think...

Mine was working last night but it wouldn't surprise me if I went to the garage right now and found it screwed up again  :o

The whole thing has been terribly frustrating to me...
Jon


Little by little I have grown fond of the infamous Auto Temp II we have in our 116's

jbrasile

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Re: ACC is working! Sort of...
« Reply #7 on: 13 May 2011, 07:14 AM »
Guys,

Always start diagnosing these system by testing for vacuum leaks as 1980sdga did. Go to the fresh air door actuator first and isolate it if it looses pressure. Once you are confident that no leaks exist make sure the servo and amp work. What 1980sdga did by replacing the servo hoses and lubing the disc I had never heard or done before, nice work!!!

Again: if there is a leak and the two switches behind the glove box don't get vacuum, nothing will work!

And I can't stress enough, try to keep things as simple as possible because systems interact in the acc and you will go nuts trying to chase a problem.

1980sdga, I didn't know your system was converted so I'd just check to make sure the drier was already changed along with the oil and do a re-charge, no need to replace anything if the conversion was done properly.

I read here in the forum that replacing the expansion valve with one calibrated for R134 will increase a/c performance so it might be a good idea to do that too.

Tks,

Joe


Casey

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Re: ACC is working! Sort of...
« Reply #8 on: 13 May 2011, 08:11 AM »
Well Raptelan, you asked a question that Joe answered which helped me piece the puzzle together

Glad to be of service then.  Asking stupid questions is one thing I'm great at.  I've never worked on cars at all before - never really had the interest until I finally took ownership of a W116.  So it's a whole new scary world to me.  But that's exactly why I'm trying to do everything myself on this car - more than saving some money and being able to do more - I want to know where everything is on this car and understand it.  The vacuum stuff is pretty mind-boggling and I don't even know where to start.  After my trip I will probably just start investigating vacuum links one by one, get some sort of testing tool, etc.  I don't really think my servo works but have not investigated.  I know there are vacuum leaks though because the auto locks don't work after the car has been off for a minute, and never works on the rear driver-side door.  Plus there is some sketchy "repair" patchwork on the brake booster vacuum line with silicon.

So you replaced loads of hoses?  Did you order some kit for this or just use some generic stuff?

BWalker82

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Re: ACC is working! Sort of...
« Reply #9 on: 13 May 2011, 08:17 AM »
I'm pretty sure I don't have a blower.  I can, however, hear something "parking" like the elec. schematics & you guys mention after the car is switched off.  

I know there are leaks somewhere in my system as it prevents my car from shutting down (the OM617 requires a strong enough vacuum to pull the fuel stop) while anything but OFF is depressed on the climate panel.  I've also read lack of proper vacuum prevents the fan from even engaging.  

-BW
-BW

Casey

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Re: ACC is working! Sort of...
« Reply #10 on: 13 May 2011, 08:21 AM »
I know there are leaks somewhere in my system as it prevents my car from shutting down (the OM617 requires a strong enough vacuum to pull the fuel stop) while anything but OFF is depressed on the climate panel.  I've also read lack of proper vacuum prevents the fan from even engaging.  

I've got that issue too.  I didn't realize at first that I needed to have the ACC in OFF - I almost ordered up a new shutoff valve.

So it sounds like our cars are in the same boat, plus my servo might be dead.  I replaced the fuse (which was not even there when I bought the car), but haven't heard any new noises since then.  I'm definitely interested in anything you might do or figure out.  Please share pictures if you can. :)

BWalker82

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Re: ACC is working! Sort of...
« Reply #11 on: 13 May 2011, 08:23 AM »
Well Raptelan, you asked a question that Joe answered which helped me piece the puzzle together

"Glad to be of service then.  Asking stupid questions is one thing I'm great at.  I've never worked on cars at all before - never really had the interest until I finally took ownership of a W116.  So it's a whole new scary world to me.  But that's exactly why I'm trying to do everything myself on this car - more than saving some money and being able to do more - I want to know where everything is on this car and understand it.  The vacuum stuff is pretty mind-boggling and I don't even know where to start..."

I've been working on cars myself since I was a teenager.  With the right tools, the right instructions, and forums like this, you can do any thing you want.  It's all just nuts and bolts at the end of the day.  Something to fear is a clutch change on a Porsche 944... that'll leave you a different, angry man.

This vacuum stuff is foreign to me as well.  Have you looked at the vacuum diagram for this system in the manuals?  I'm wishing there was a way to swap everything to a manual system, like the Europeans have... even if aftermarket.

-BW
-BW

Casey

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Re: ACC is working! Sort of...
« Reply #12 on: 13 May 2011, 10:40 AM »
This vacuum stuff is foreign to me as well.  Have you looked at the vacuum diagram for this system in the manuals?  I'm wishing there was a way to swap everything to a manual system, like the Europeans have... even if aftermarket.

I have no manuals of any kind.  Just the internets.

There is a way.  It's very expensive to buy NOS OEM parts, or you can buy a donor parts vehicle.

jbrasile

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Re: ACC is working! Sort of...
« Reply #13 on: 13 May 2011, 01:40 PM »
Casey, the factory CD is avaiable right here for free!

http://handbook.w116.org/matrix6.htm

If this link doesn't work just go to the bottom of the page and click on "Service Manual Library" This will greatly facilitate your work not only on the acc issue but for several other tasks involving your car.

Have fun!

Tks,

Joe

BWalker82

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Re: ACC is working! Sort of...
« Reply #14 on: 13 May 2011, 05:18 PM »
Definitely check out the links above... lots of info there... if not too much.  Our ACC-II is more complex than I would have ever imagined, esp. for an auto circa 1980.  They devoted an entire manual it seems to the ACC-II, just like the engine, and chassis. 

I wish they went into more detail on some things, but I guess the manual assumes an ASA/MB Certified Tech would be interpreting it more clearly than the layman with a new torque wrench to play with.

Keep us updated so I know what mistakes to avoid when I tackle mine later.

Cheers!
-BW
-BW