Author Topic: ACC is working! Sort of...  (Read 6054 times)

Casey

  • W116 Addict
  • ****
  • Posts: 1,735
  • Location: Maryland, USA
Re: ACC is working! Sort of...
« Reply #15 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.

jbrasile

  • W116 Addict
  • ****
  • Posts: 1,217
Re: ACC is working! Sort of...
« Reply #16 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

1980sdga

  • Vintage
  • ***
  • Posts: 813
  • Location: Ga. USA
Re: ACC is working! Sort of...
« Reply #17 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.
Jon


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

jbrasile

  • W116 Addict
  • ****
  • Posts: 1,217
Re: ACC is working! Sort of...
« Reply #18 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

1980sdga

  • Vintage
  • ***
  • Posts: 813
  • Location: Ga. USA
Re: ACC is working! Sort of...
« Reply #19 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:



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:

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:

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:



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".
« Last Edit: 15 May 2011, 10:28 AM by 1980sdga »
Jon


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