[W126 Coupe] RE: MBCOUPES Digest, Vol 22, Issue 19

[Dick Spellman]

Hi Jack:

I've done all the elements several times and never needed to remove the 
center vents.  Which element are you referring to?

Dick

Jack wrote:

>Hi Dick,
>
>I found that the vacuum lines on the switching vales were leaking. When I
>applied 25hg on the center console the element ruptured. Now I get to change
>that one! I wish I would have known about the 15hg part! The manual says you
>have to remove the console and the center vents to get to it. Waahhh... Do
>you know of an easier way?  Fixing the switching valve problems got the air
>blowing out the right vents finally.
>
>I'm still sorting out the heat blowing out the vents all the time. I'll try
>the functional test as you recommend 
>
>Good thing I'm doing this myself. A shop would have charged me about what
>the cars worth to fix this. Next up, a new a/c compressor and replacement of
>a leaky fuel return line. 
>
>If this car didn't drive so well, I would have got rid of it a long time
>ago. At least we have a well equipped garage, even have a scope and 4-gas
>here.
>
>Thanks again!
>
>Jack
>
>++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>I would recommend you run the tests in 83-601 to see where the fault(s) lie.
>If no air is coming out the center vents it's being diverted to the defrost
>vents and/or to the leg area. If you can access the vacuum switch valve to
>the right of the center console and have a Mighty Vac
>(MV) handy, you can test each of the individual vacuum elements one more
>time without having to get at each element directly. Just unplug the
>respective vacuum line and run the connected MV up to 15 hg or so and let it
>sit for a minute to see if the needle creeps lower. (I wouldn't go much
>above 15hg to protect the rubber diaphragms from rupturing) If all the
>elements and their respective vacuum lines check out, then one remaining
>possibility is that one of the element linkages is stuck or a pivot on say
>the leg flaps is broken in the heater box. I found that
>83-601 done in an orderly fashion pretty much gave me the details of what
>needed fixing.
>
>By the way, I just replaced the complete ACC head last weekend in the 86
>300SE with a rebuilt (warranty 2 or 3 years) from Ken at
><www.thebenz-store.com>. This was the sedan that I rebuilt the ac and vac
>elements on 2 years ago. Worked fine for 2 years but, started behaving in
>such a manner a few weeks back that I once again ran the tests in 83-601 and
>determined that the head unit this time round was all done. An important
>note found on the new unit instructions says "check that there in no reading
>at or close to 0-ohms resistance on both the mono-valve head and the coolant
>recirculating pump as an external short on either of these components will
>damage and void the warranty on the acc push-button unit". So, as an
>additional test you can and should check these two devices with an ohm meter
>with electrical disconnected to see if they are working showing and open vs.
>a short as the instructions recommend. I tested both my units before
>installing the new head unit and found them to be in working order. I took
>the added step of running 12VDC across each unit to see/hear the operation
>was as it should be... Clicking on the solenoid element for the mono-valve
>and the buzz and sounds of coolant being pushed though the heater core on
>the recirc. pump.
>
>The behavior I just dealt with was in fact the vacuum switching valve
>changing air distribution locations erratically along with the 'Auto' 
>button having been selected causing wild shifts in the fan speed. Every time
>I'd hit a bump in the road the system would start mis-behaving. 
>Again, I diagnosed using 83-601 before laying out $155 to effect the repair.
>I didn't bother withthe cold solder joint repair where I had done this 2
>years earlier and felt that after 20 years a reman was in order.
>
>Good luck, keep at it.
>
>Dick
>
>Jack wrote:
>
>  
>
>>Hi again,
>>
>>Ive got the vacuum elements switched out, no more leaks. But the air 
>>wont come out the center vents.
>>
>>Anything other than max a/c also blows hot air. Not good when its 
>>already 100 degrees out here. I changed out the mono valve too.
>>
>>What the heck is going on with this thing? The center vent (40) 
>>element didnt leak but I dont hear any movement when adding vacuum.
>>
>>Looks like a pain to get in to that one!
>>
>>Jack
>>
>>-----------------------------------------------------------------------
>>    
>>
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