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Garage => Mechanicals => Topic started by: 1980sdga on 12 May 2011, 06:00 PM

Title: ACC is working! Sort of...
Post by: 1980sdga 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! 
Title: Re: ACC is working! Sort of...
Post by: jbrasile 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

Title: Re: ACC is working! Sort of...
Post by: 1980sdga 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.
Title: Re: ACC is working! Sort of...
Post by: Casey 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!
Title: Re: ACC is working! Sort of...
Post by: BWalker82 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
Title: Re: ACC is working! Sort of...
Post by: Casey 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.
Title: Re: ACC is working! Sort of...
Post by: 1980sdga 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" :

(http://i711.photobucket.com/albums/ww112/jhoff/zvacuum.jpg)

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...
Title: Re: ACC is working! Sort of...
Post by: jbrasile 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

Title: Re: ACC is working! Sort of...
Post by: Casey 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?
Title: Re: ACC is working! Sort of...
Post by: BWalker82 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
Title: Re: ACC is working! Sort of...
Post by: Casey 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. :)
Title: Re: ACC is working! Sort of...
Post by: BWalker82 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
Title: Re: ACC is working! Sort of...
Post by: Casey 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.
Title: Re: ACC is working! Sort of...
Post by: jbrasile 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
Title: Re: ACC is working! Sort of...
Post by: BWalker82 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
Title: Re: ACC is working! Sort of...
Post by: Casey on 13 May 2011, 05:48 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.

Yeah, but it doesn't have one specifically for my model/year.  I want to pick up a paper copy at some point.
Title: Re: ACC is working! Sort of...
Post by: jbrasile on 13 May 2011, 06:04 PM
Casey, I am talking about the repair manual, not the owner's manual. The Service Manual Library covers all US 116's including the 300SD from 78 to 1980.

The owner's manual available is for the 450SEL, but excluding the mechanicals, the cars are almost identical, acc, controls, etc... are all the same.

The repair manualis where you will find all the procedures to diagnose and repair problems.

Tks,

Joe
Title: Re: ACC is working! Sort of...
Post by: 1980sdga on 13 May 2011, 09:36 PM
Yea Casey, click through the "Library" on this site and you'll find everything you need. And then some...

I printed most of it out and put it in binders.

There is also some useful ACC info here:  http://www.imperialclub.com/Repair/Lit/Master/281/intro.htm

I'm on the road now but when I get home I'll post some pics of what I used for vacuum testing and some of the stuff that got me to the point I'm at.

Hey Joe, my AC was converted to 134a on 10/10/01. Do you think I need to change the drier? I hate to open the system but I understand the drier can fail and screw up the whole system by flooding it with junk.
Title: Re: ACC is working! Sort of...
Post by: jbrasile on 13 May 2011, 09:43 PM
1980sdga, yes, it's probably a good idea to replace it. If you buy aftermarket they are fairly inexpensive.

Tks,

Joe
Title: Re: ACC is working! Sort of...
Post by: 1980sdga on 14 May 2011, 09:04 PM
Will do Joe.

Here's some pics of how I went about troubleshooting.

This is where I disconnected ALL other vacuum systems other than the trunk mounted reservoir and  the ACC system:

(http://i711.photobucket.com/albums/ww112/jhoff/IMG_2168.jpg)

The green/black line runs straight to the switch panel where the whole AC system branches off from.  The yellow/black line goes back to the reservoir.  The tee goes to the vacuum gauge. You can hook your mity vac up the way I have the gauge connected but the big gauge helps me see what's going on when I'm inside the car. The check-valve (or one-way valve) keeps the vacuum that is pulled on the reservoir and AC system from bleeding back through the vacuum pump.  The grey line goes into the vacuum pump to brake booster trunk.  The check valves in the main trunk also keep the circuits isolated and it's pretty easy to check them out.

I started with the reservoir and checked it with the mity vac. I then put the gauge on the tee and let the engine pump pull a vacuum on JUST the yellow/black (reservoir) line. Once that was OK and held vacuum for a couple of hours I hooked the green/black (AC) line up.

Before testing the whole system using engine power I checked all the circuits through the switch panel vacuum lines with this:

(http://i711.photobucket.com/albums/ww112/jhoff/IMG_2170.jpg) switch

I then just checked each line by pulling a vacuum on them with the mity vac.  Some of them bleed over to other lines at the switch panel so You'll have to study the diagram to see what goes where.  I used a crayon to mark each line on the diagram as I checked it.  When there were no leaks and the whole thing was colored I figured I was done  ;D

One of my trouble spots was here:

(http://i711.photobucket.com/albums/ww112/jhoff/IMG_2169.jpg) servo

Most of the vacuum lines were leaking where the rubber lines hook to the plastic rectangular connector so I just CAREFULLY changed them out one by one. Probably not a bad idea to draw a diagram before starting because it was easy to knock several lines loose while working on one. It's like a friggin' maze  :o

You can also use these lines as a source for pulling a vacuum for testing and plugging them to pull a vacuum from inside the car. Oh yea, don't try plugging with screws  ::)  It was driving me nuts until I realised that vacuum was leaking around the threads  :-\ The shank ends of drill bits worked best for me.

You can also have leaks here:

(http://i711.photobucket.com/albums/ww112/jhoff/zvacuum.jpg)

This valve appears to rely on vacuum to keep the rubber sealed against the metal part with the holes in it.  (The rubber part is rotated by the servo motor while the part with the holes in it remains stationary.) The vacuum just "sucks" it together. I swear it looks like there is room for 4 springs under it to keep the discs pressed together but I didn't find any in either of my servos and they were both sealed... I put a light spring under mine and it solved a bunch of problems.  My only fear is that it may wear out the rubber too soon.

This vacuum switch also runs the elusive center flap function.  The center flaps aren't open when the system decides you need full heat. Turning the wheel from 85 down to 65 manipulates the servo which magically opens the center flaps after a short delay.  Moving the wheel from 65 to 85 will close the center vents and change the airflow to the lower ducts.   An electric "wiper" type switch in the servo adjusts the blower speed and probably does some other stuff that I haven't figured out  ???

Sorry if this is long winded and I hope it makes sense!  I'm not the sharpest cat on the planet and it took me several days to figure out enough of what I was doing to get anything done  :-\  I hope this helps someone get started and figure out some more stuff  ;D

I tested the system tonight after letting the car sit for a few days and all looks well.  The reservoir pumped down to 15in/hg in about 5 minutes and only bled down to 10in after 45 minutes with the engine off.  Manipulating the controls did bleed it down further but nothing caused any kind of instant "dump".