Author Topic: Semi-Automatic Climate Control modification  (Read 3952 times)

1980sdga

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Semi-Automatic Climate Control modification
« on: 22 April 2012, 09:50 AM »
I just wanted to preface this by saying that the BEST solution to ACC problems is to properly troubleshoot the system and return everything to factory specs.  I did this on my daily driver and there's something really satisfying about having such a nifty system operating as it should. It's also a very good system when working properly!

Unfortunately it can also be an expensive system to rebuild. It cost me about $700 to get mine working  :o Roughly $500 for a servo, another $100 or so for the amp, a little more for the pods that had failed...

Proper ACC II function relies on 5 vacuum pods, 6 electric/vacuum switches, the servo, an amplifier, a "sniffer" thermistor and enough vacuum lines to circle the globe  :o  Add to that the wiring necessary to keep everything humming and you have a pretty complex system dedicated to keeping your @ss comfortable... I won't even go into the auxiliary water pump which is responsible for so many woes  :-\

Neat, but unnecessary...

I've read about everything on the interwebs about the ACC II and I've seen folks go to great lengths just to get some heating or cooling in their cars when the system has gone kaput and left them with either no heat or scorching heat with no control and no air out of the center vent  :o

Solutions have included installing a push/pull knob for controlling water flow to the heater core, which seems rather crude in a Sonderklasse, the infamous UT kit which is expensive and won't help if you have vacuum/pod troubles and some guys who have retrofitted entire switch gear from other cars. Plenty of us lust after the manual systems and dream of doing a retrofit into our cars but even that looks daunting and would probably require a parts car to get it sorted.

About a year ago I started this thread:

http://forum.w116.org/mechanicals/altering-acc/msg84573/#msg84573

And since then I've been tinkering with the ACC trying to figure out a simpler/cheaper way of doing it and maybe help some fellow 116 pilots enjoy they're cars without spending a ton of $$ on something as simple as a HEATER!

The first obstacle I ran into was the automatic center vent flap. Here's a peek-a-boo shot of what is required to operate it:



On the far right you can see the passenger side defrost duct. The center opening with the pods above it is the center vent opening with the automatic flap assembly removed. The opening on the left with the flap open is the drivers side defrost opening with the duct removed.

The pink pod on the right is for the automatic center vent flap and the white one is a double acting pod for the defrost. The defrost pod has 2 positions, half open and full open. It's full open for DEFROST, half open when BI-LEVEL is selected, closed for cooling and it's connected to the center vent pod via a vacuum line. It appears as if  the defrost pod starts leaking it closes the center vent and opens the defrost flap. It's a safety feature to insure that you'll still have full defrost if something goes wrong.

This was my quick and dirty solution:



I pulled both pods and moved the pink single acting center vent pod over to the defrost position. Now I only have ONE pod and ONE vacuum line running the defrost flaps instead of the THREE lines it had previously. No automatic center vent flap but there is still a manual flap ONE INCH AWAY from the automatic one  :o

The pods are held in by little friction washers that you can pry off with a screwdriver.

I did have to change the metal actuator arm from the white pod to the pink one but it's pretty easy to do once you open the pods up. Sorry I didn't take pics but it's pretty simple to do once you get the pods out.

Here's a picture taken through the dash opening with the defrost duct removed:



This helped a great deal with gaining access to the center pods. It's held to the dash with little metal tabs folded over and you can reach in and straighten them out and fidget the duct out:



It's a 2 piece affair held together with VERY SHARP staples so be careful! You can see the 3 square openings for the metal dash tabs on the top side of the duct. It came out in 2 pieces. It was fiddly but it did come out after some work!  I would be leery of trying this if I had a pristine dash in this car because I had to flex the duct up through the defrost openings to get it out and it would SUCK to mess up a nice dash in the name of lazyness!  I didn't damage my dash any more but you'd have to be VERY CAREFUL!

Here's a picture of the center vent nozzle with the automatic flap removed:



It's held on with 2 little metal clips on either side. I didn't take pics of the disassembly but it's pretty straight forward. Just remove the registers by carefully prying the retaining pins on either side with a screwdriver and they slide out. It helps to point them down as far as they will go and rotate them downward as you pull them. This will give you access to the metal arm on the "pink pod" and you can separate it from the flap with some needle nose pliers.

After the registers are out you can remove the vent after removing 2 phillips screws on either side and working the rubber boot off the nozzle.

Here are the 2 pieces out:



After working the vent assembly out. (It'll come out through the glove box opening) you can pull the little metal clips holding the nozzle on and wiggle it out.

Now I have normally open defrost ducts that will close with vacuum applied and NO automatic center vent to fail  ;D

So what now?


I applied vacuum to the pushbutton assembly and attempted to map it's vacuum function:



The map isn't correct because I neglected to notice that nipples 1,2 and 3 are connected together via the rubber plug that connects to the back  ???  Never assume with MB...

The only switching I had to work with were ports 4,5,6 and 7. Fortunately #6 has vacuum with either OFF, AUTO LO, AUTO HI and no vacuum with BI LEVEL or DEFROST.  Since the defrost vent is closed without vacuum I only have windshield air with BI LEVEL or DEFROST and full vent air with AUTO LO and AUTO HI!  So far so Good!

The center nozzle with no flap or flap pod:



The vent installed:



You can see the rod that actuates the 2 defrost flaps and the actuator arm through the opening.

Now for blower speed control...

MB designed in another failsafe into the system here:



The green vacuum switch on the left switches power to the blower ONLY when vacuum is applied. The yellow is for the AC compressor. No vacuum here, no blower other than pressing DEFROST.  I discovered through my little mapping adventure that nipple # 5 provides vacuum in all positions other than OFF. Great! I just ran it to a splitter and hooked it to the 2 switches behind the glove box.

Now we have air out of all the dash vents and selectable defrost  ;D  No automatic center vent so you'll have to reach up there and shut it yourself if you want it closed.

Here's a picture of what's going on behind the ACC panel:



It's a bit sloppy because I'm still in the testing phases but the vacuum routing is VERY SIMPLE. 

The black line (#2) is vacuum from the engine compartment.

The purple line (#6) runs to the defrost pod.

The black line (#5) runs to the blower and compressor switches behind the glove box.

The blue line (#4) provides vacuum when either DEFROST or BI LEVEL are depressed. (Same as #6) I'm going to try using it to switch a vacuum actuated heater valve so those 2 buttons will be for heat.

Here's the heater valve part:



It's a valve from a 1979 Chevy V8 PU (About $10)  I hooked it into the same line (Purple, #6) as the  defrost pod so now the heat valve is open with the panel in either DEFROST or BI LEVEL.

I'm using this:



to switch blower speeds.

It's just an old servo with the bottom half cut off. The water valve part of the servo is what either starts leaking or binding and causes problems. The top portion of the servo is actually pretty robust with little to go wrong.  In hindsight, it would have been much easier just to take it apart and cut the little "drive shaft" off. This would have left the metal water valve part intact which would have allowed mounting using the original bracket.
« Last Edit: 22 April 2012, 04:14 PM by 1980sdga »
Jon


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

ckamila

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Re: Semi-Automatic Climate Control modification
« Reply #1 on: 22 April 2012, 04:56 PM »
Did you need to match the amp with the servo? I am in the same boat and you suggested i order servo and amp together. I did order the servo from George Murphy but not the amp. My thinking was why drop another $100 into this project if the it's working and easy to replace if needed. Would a failing amp take out the servo?

My blower was working intermittently. Problem was dirt/junk deposits internally which i found once blower was removed and during examination stuff was falling out the small hole of black feedback tube connection. I kept rapping the blower with the butt end of a screwdriver and shaking the blower until no more junk fell out. Has worked since.

Great work around and pictures. Waiting for the next update....


chris
If it's not broke i haven't fix it yet...


1980 300SD, 170K
1985 300D, 235K

1980sdga

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Re: Semi-Automatic Climate Control modification
« Reply #2 on: 22 April 2012, 05:56 PM »
Joe is the real expert here but this is my take on it FWIW.

They don't have to be "matched" but I believe that an old dragging servo can cause the little servo motor to draw too many amps and heat up the amp. Believe it or not the amp can become too hot to touch before blowing the fuse!  This heat can cause the old solder joints to fail and the system will stop responding. Oddly enough, when it cools it can begin functioning fine again on it's own only to stop again after it gets hot  :o

It was quite maddening until I figured out what was going on!

You did the right thing by ordering from Mr. Murphy! I got impatient and ordered a "rebuilt" aluminum servo from an ebay seller. It required disassembly and lubrication before it would work right!  I got a rebuilt amp from GM before I got the whole thing sorted and all is well now!

I would try out your old amp before getting another one. I've never heard of an amp damaging a servo so I think you'll be OK.

You may want to do a thorough coolant flush before installing the new servo. The water valve portion of the servos can be picky about trash getting in them. It wouldn't be a bad idea to run MB coolant to protect the seals in it as well. It's also probably good for your engine  too ;D

I'm waiting for you to update as well so get off your arse and do something! 

Would you mind if I linked to some of your pics on a thread I started  over on PP?  Your evaporator rebuild is epic and inspiring! I already linked back to your evaporator thread because it has such GREAT info and pictures!

« Last Edit: 22 April 2012, 06:02 PM by 1980sdga »
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: Semi-Automatic Climate Control modification
« Reply #3 on: 22 April 2012, 08:30 PM »
Tks for the "expert" Jon! hehehe....


Chris, no, the amp will not damage the servo, happens the other way around as Jon says, the servo starts to get sluggish, draws too many amps and the amp fries... try your old amp but after all you've gone through I'd just get a new or rebuilt one from GM.

Tks,

Joe


ckamila

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Re: Semi-Automatic Climate Control modification
« Reply #4 on: 22 April 2012, 09:11 PM »
Jon - i figured everything is up for grabs when posted in the library so please help yourself.

I know...i know... i have spent too much time on other things (kids (3), wife, flu, work, vacation) and this project has gotten quite large but the i have run out of procrastination ideas so i am seeing light at the end of the tunnel. Last week i reinstalled the metal water lines, disassembled the window washer pump (have pictures  8) ) and repainted the rusted mounting bracket. Today i reinstalled the brake booster after repainting and hopefully tomorrow i will install master cylinder and possibly the evap box :o . Joe is sending a box of goodies that should arrive in the next day or so.

Joe - thanks for the suggestion.



chris
If it's not broke i haven't fix it yet...


1980 300SD, 170K
1985 300D, 235K

jbrasile

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Re: Semi-Automatic Climate Control modification
« Reply #5 on: 22 April 2012, 09:14 PM »
Chris,

Parts should arrive on Wednesday, I will e-mail you the tracking number and invoice tomorrow.

Tks,

Joe

1980sdga

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Re: Semi-Automatic Climate Control modification
« Reply #6 on: 23 April 2012, 08:17 PM »
That's going to be a fantastic car when you're finished Chris! Yea, sometimes it is hard to find time for our machines.

I heard that Joe even takes a breather now and again  ;)

Here's a little after work progress on my hack:



Water valve installed. 

I decided to keep the aux. pump even though a PO hacked the wiring up. It's a pretty simple setup that you can see here on page 16:

https://s3.amazonaws.com/sspublicweb/mercedes/Mercedes+116+Climate+Control+Service+Manual.pdf

(Thanks to Sshanky for uploading it!)


It's a simple circuit that uses a thermostatic  switch which applies power when the temps are below 79F.  I'm planning on installing an in-line fuse near the pump. Hopefully it will keep the main fuse from blowing should something go wrong.

I'm using my "semiservo" to control the blower speeds through the ACC sensor chain.  No vacuum or water will be controlled via the servo.

I was thinking about experimenting with the vacuum switching portion of the servo and attempting to have the heater valve open when the servo swings to the "hot" side. I'm not sure if it'll be possible considering that the water valve is open with no vacuum and closed with vacuum applied. The control wouldn't be as precise as the original setup but it may work.

Any input?

If anyone else is considering modifying their system without using the servo at all you may want to look at pages 20-27 of the document I posted. You could just jump across the electric plug that goes to the servo and have one of the 5 speeds that the servo/resistor block is capable of. I believe that it would give you 3 speeds switched via the push button panel.

So far I have about $20 in this project  :)

The soup kitchen is open  8)
« Last Edit: 24 April 2012, 05:17 PM by 1980sdga »
Jon


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

1980sdga

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Re: Semi-Automatic Climate Control modification
« Reply #7 on: 24 April 2012, 05:47 PM »
Another update.

I studied the servo electrics some more and discovered that there is no way to use the blower switch in the servo for opening the water valve. It seems that both the hot and cold sides of the blower speed switch mirror each other. The only difference is an additional high speed on the cold side.

I did some testing with the engine running today and was happy to find that the water valve seems to work great!  It only opened when either BI-LEVEL or DEFROST was selected and was closed in the other positions.  The blower speeds are automatic and as the interior warmed the blower speed first dropped and then began to increase as the servo swung to the cooling side. Unfortunately nothing triggered the valve to close so it just got hotter and hotter!  Nothing wrong with the basic heater function in the 116  ;D

Since this worked out so well I decided to go a little further and explore the vacuum switch on the servo and attempt to get some rudimentary "automatic" control.

I started by doing some mapping of the valve:






After some tinkering and head scratching I tested it with a vacuum source connected to #6 and the normally open valve to #5 now the valve  remains closed until the servo turns almost all the way to full heat  ;D  Not as precise as the adjustable valve that the factory uses but it does switch off and on automatically.

I didn't test it with the engine running but I did run it through it's paces hooked up to a vacuum pump with a gauge for monitoring when the heater valve was open or closed.  The ambient temp was 72F in the garage and I noticed the heater valve opening when the thumb wheel was on about 75F and closed when it was around 70F and below!!

So far so good!

Here's a pic of the underhood testing:



I'm soooo ready to tidy everything up and try it out!

Another picture of valve and hose routing:



Jon


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