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  #1  
Old 05-07-2011, 09:54 PM
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Divin' into the 116 ACC...

When I test drove my car originally the AC was on "Hi" and it blew cold air like a boss. I fiddled with the controls to check the defrost and it blew hot out the defrost vents but kind of hung there...

I used the fouled up AC for bargaining and drove the car home.

On the way home (About 600 miles.) the heat became too much so I pulled the AC fuse to kill the blower.

Somewhere along the way the engine lost the ability to turn off *sigh*

I put the controls back on "hi" and replaced the fuse and the AC was cold again so I rolled with it.

Anyway, this AM the defrost was back on (I didn't manipulate any controls).

I tried the fuse boogie again and nothing. I also noticed that the #3 fuse is REALLY warm.


Sooo,

#1

I'm pulling the pass. side ducts under the dash to check the "recirc" pod. If it's leaking I'll plug the lines. It must be a pretty good leak to prevent the engine from stopping right? The AC vacuum controls are somehow fouling up the engine shut off.

#2

Look at the ACC amp for any obvious defects.

#3

Lube the blower motor. (Causing the fuse to run hot?) Need brushes as well.

#4

Check the auxilliary pump for function. I'm sure it works because the heat seems fine.

Any other advise?

I'm going in...

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  #3  
Old 05-07-2011, 11:06 PM
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Quote:
Originally Posted by leathermang View Post
It really sounds like you have a vacuum leak... most of those symptoms fit that....
Gotta be. I manipulated the ACC buttons some more and the engine turns off now

I pulled the pass. under-dash stuff and the glove box liner and didn't see anything obvious.

The big "recirc" pot isn't leaking and appears to function when the buttons are pressed. I did see 2 lines behind the glove box (one black, one white) which weren't capped or anything. Just open ends...They don't look like they were EVER hooked to anything. I didn't see any other hoses that were unhooked or any cracked rubber etc.

I also checked the 2 "bundles" under the hood as well. The one by the ACC servo and the one near the brake booster. Nothing obvious...



I pulled the amp and found several cold joints that appear to be making poor contact if any. You can see them in the pic

I need to find the vacuum leak but I'm pretty lost No need fixing the amp until I've straightened the leak out.

I guess the next step is pulling the ACC control panel and looking back there.
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  #4  
Old 05-07-2011, 11:15 PM
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I would suggest starting at the vacuum pump and heading out... you might get lucky...
Check your check valves and as old a car as it is.... you might consider putting new lines on from the pump... hard to see a small crack leak on the underside of a rubber hose...

I do not know which type of AC system you have..
but the type 2 and 3 on the 123's ....JUST that dash unit you mentioned taking out .... diagnostics section is 80 ( EIGHTY !!!) pages long.... hope that something can be fixed somewhere before you get to there....
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  #5  
Old 05-07-2011, 11:58 PM
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WTF???




These are under the instruments. One of the 3 way deals is open (I understand that there are some "open" circuits) and there is an open hose!

There is NOOO way these were connected together because they won't reach. Kind of funny that all 3 of the lines are a kind of translucent white and the same diameter though...

The hoses to the 3 way come from the engine compartment and the open hose snakes it's way towards the center of the dash...
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  #7  
Old 05-08-2011, 12:50 AM
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Dug a little deeper...

View through the dash with one of the ducts out of the way. I have 3 plastic tubes the same diameter and a 3 way "spider" deal.

Should I hook them up and see what happens?

I like the mechanical oil pressure gauge but sometimes it's a PITA...
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  #8  
Old 05-08-2011, 12:54 AM
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Be sure your parking brake is ON...
LOL
I do not know if anything bad could happen....sure seems like they are meant to be connected.....

How about a klepto mouse in your car... needed that vacuum line somewhere else ? Also known as ' pack rats ' ....
Will carry things off just like a crow....
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  #9  
Old 05-08-2011, 04:08 AM
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Crazy, I hooked those 3 lines up and re-soldered the joints on the amp.

I fired the car up and tried the AC. I get different blower speeds but I have the dreaded "No center vent" blues...

Strange the way it was working, then not, and I removed/reinstalled the fuse and it started working again. Then died on it's own.

I had the ignition on and I heard the servo working with the thumb wheel. It seemed to move incrementally with the wheel which was promising!! I did notice that the amp got pretty hot. No smoke or anything, just really warm.

So I fired up the car to see if the wheel was controlling the temp but I couldn't really tell

Then I shut the car off and now I can't seem to get the AC to work without the engine running. It'll work for about a minute (The blower changes speed) but I can't hear the servo over the blower and auxilliary fan.

The engine still won't turn off with the wrong button pushed (I need to start writing it down) but I did change from one setting to another with it running and it shut off. This is a clue...

I guess I need to get a service manual to check out the WHOLE AC system.

I would REALLY like to get this system working!

I don't imagine the center vent pod is routed through the amp or servo?

Where exactly is the pod that runs the center vent and how do I test it?

Thanks
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  #10  
Old 05-08-2011, 05:42 AM
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I guess my servo died I had another servo that I took apart and hooked it up. I could turn the wheel and see the little servo motor turn so I figure my amp must be OK. I can tap on the servo and it'll start working again, although slowly...

While testing I turned it the heat all the way up and tested for voltage at the auxilliary pump and got nothing. I tested/oiled it and it works fine.

Now if I could find the vacuum leak and get the center vent working. Haven't found anything visually and the lines I hooked up did nothing.

My door locks work sometimes and they feel kind of stiff. The vacuum reservoir doesn't seem like it holds a vacuum very long after the car is turned off. It's gotta be related because how else could my AC keep me from turning the engine off? The brakes feel fine so I don't think it's a vacuum pump issue.

I'm going to look closely at this thing:
http://www.imperialclub.com/Repair/Lit/Master/281/page08.htm
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  #11  
Old 05-08-2011, 02:31 PM
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Ok,

On later W116's, there is a separate, inline fuse in the fuse box for the auxilliary water pump.

Several causes of blown #3 and #9 fuses on W116's. The single most common cause of blown fuses on A/C and DEF operation is a shorted A/C low pressure switch in the drier. Disconnect this to verify.

Second most common cause is either dry bushings in the blower motor and/or burned/mis0aligned contacts in the double pole blower relay behind the glovebox.

With the blower operating, wiggle the connector on the blower relay. If the blower speed changes, take the unit apart and file/straighten the contacts.

Also, you need to verify that the foam hose between the evaporator case and the in-car temp sensor (on the dash) is intact. They are almost always rotten and will cause the ACC system to 'hunt' back and forth between A/C and heat.

A quick fix is a 3 foot section of 1/2 household pipe insulation from your local hardware store.

Vacuum is critical to getting this syetm to work properly. Be sure to inspect the check valves underhood in the gray vacuum supply lines from the vacuum pump. A bad check valve is another common cause of vacuum loss. Also check the vacuum storage unit in the trunk.
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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 05-08-2011, 02:36 PM
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Quote:
Originally Posted by 1980sd View Post
I guess my servo died I had another servo that I took apart and hooked it up. I could turn the wheel and see the little servo motor turn so I figure my amp must be OK. I can tap on the servo and it'll start working again, although slowly...
You must follow the test procedure and verify that all of the voltage and resistance values are correct. You cannot assume the amplifier is good based on this sort of test.

Quote:
Originally Posted by 1980sd View Post
While testing I turned it the heat all the way up and tested for voltage at the auxilliary pump and got nothing. I tested/oiled it and it works fine.
Check the inline fuse in the fues box.

Quote:
Originally Posted by 1980sd View Post
My door locks work sometimes and they feel kind of stiff. The vacuum reservoir doesn't seem like it holds a vacuum very long after the car is turned off. It's gotta be related because how else could my AC keep me from turning the engine off? The brakes feel fine so I don't think it's a vacuum pump issue.
You should go to www.w116.org and look at the testing procedures in the ACC II FSM located there.

Over 75% of the servos I harvest from Pik-N-Pull actually work fine. The biggest servo problem is a coolant leak, either externally or internally. However, I find very few bad servos and far more items in the system that appear to be the servo's fault.
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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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  #13  
Old 05-08-2011, 04:02 PM
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Thanks Doc! I was hoping you'd chime in. I'm working on a friends car today (My old CTS-V. I keep thinking it's mine ) but I'll be back on the Benz this evening.

I'll check what you outlined and change the "sniffer" hose, mine was pretty well gone.

How do you test the check valves? I assume they are the plastic in-line parts? are they supposed to only be one way? Sorry, but I'm learning...

I have a mity vac but I'm not sure what to do with it I was hoping it'd be a magic bullet...

This car is my daily driver. Wife said I was crazy, must prove her wrong...
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  #14  
Old 05-08-2011, 07:38 PM
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Yes. The check valves should flow in only one direction...

My wife is now using my W116 daily for her Mary Kay business. I feel like I work for a motor pool nowadays.

Be sure to check the ACC II FSM at www.w116.org and follow the test procedure...Robert
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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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  #15  
Old 05-08-2011, 11:04 PM
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I take it that this is the pressure switch? It looks like someone installed a relay at some time.

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