W116 climate servo question: - PeachParts Mercedes-Benz Forum

treetrimmer · #1 05-18-2014, 06:13 PM

I have a 1979 300SD with a bad climate control servo. Big surprise, I know.

Recently, MB has drastically lowered the price of the basically identical unit for the w123, part # 000-830-03-84. They also lowered the price of the correct w116/107 part, (don't have part# handy), but not nearly as much. There is about a $600 difference between them.

The two units are outwardly identical AFAIK and of course eBay junkyard sellers do not acknowledge that there are even two separate parts, they just advertise the w123 part as being for all models.

Does anyone know for sure what the difference between them is and more importantly, are they interchangeable? The climate systems are outwardly identical in all models of those years, dash unit, etc. We are of course talking about the early w123 system used up until 1980. Thanks in advance as always!

Ether · #2 05-18-2014, 08:36 PM

w123fanman · #3 05-18-2014, 08:41 PM

Either the aluminium one or the solid state one by UnwiredTools

cooljjay · #4 05-18-2014, 08:49 PM

Unless your servo is leaking, it may not be the issue. Remember the chain of events on the servo system....aux water pump freezes, thus blowing the amplifier, the servo doesn't usually get affected by these events, as long as the little motor inside turns...it is likely fine.....Also remember there is a sensor tube behind the glove box, this turns to dust, with out it, the system won't be able to tell the cabin temperature.

treetrimmer · #5 05-18-2014, 10:36 PM

The other components are ok, I need a servo. They fail in other ways, mine has something stuck that makes it run on and the switch-over hot water valve is dead.

treetrimmer · #6 05-18-2014, 10:41 PM

Also, a new MB servo, (w123 part listed above), is about $400 my cost. The aluminum ones are junk in my experience and the electronic hack deal is unbelievable crap. That's what I just ripped out of this car, returning it to stock but the used servo I had in my parts pile is no good.

These systems are great if everything is working properly and they haven't been "improved" by some moron. I just need to know what, (if any), differences there are between the w123 and w116 factory servo.

cooljjay · #7 05-19-2014, 01:44 AM

How do you know the parts are ok?

The only way to know if the amplifer is okay, is if it is new.....

Only way to tell if the aux water pump is good, is to pull it and test it via the battery...

I have not seen any w123/w116/w107 that has not had a crumbled sensor tube.

A bad amplifier can cause the servo to not park itself...

w123fanman · #8 05-19-2014, 04:04 AM

Quote:

Originally Posted by cooljjay

How do you know the parts are ok?

The only way to know if the amplifer is okay, is if it is new.....

Only way to tell if the aux water pump is good, is to pull it and test it via the battery...

I have not seen any w123/w116/w107 that has not had a crumbled sensor tube.

A bad amplifier can cause the servo to not park itself...

Is the sensor tube necessary for the AC to work? I assume so but wouldn't be certain. I need a new piece for my brother's 300SD. Any suggestions?

Zacharias · #9 05-19-2014, 09:56 AM

Quote:

Originally Posted by w123fanman

Is the sensor tube necessary for the AC to work? I assume so but wouldn't be certain. I need a new piece for my brother's 300SD. Any suggestions?

It's an automatic system, which means it has to reference the ambient temp to set its output temp. It can't do that if its ambient inside temp sensor isn't getting an accurate reading.

Any tubing will do. If you want to get original the part from the dealer is a length of foam and costs a few bucks (or did a few years back). Dense foam like pipe insulation works.

treetrimmer · #10 05-19-2014, 10:57 AM

The sensor tube on my 1979 300SD is rubber and it's not damaged. I have another car with a working system in it, I'll switch the amplifier but I don't think it's the problem.

So I take it no one knows the answer to the question posed in first post?

Zacharias · #11 05-19-2014, 01:08 PM

Concerning whether they interchange: The level of knowledge on ACC II isn't really that deep around here. Not that many people have messed with it extensively, usually it's specific knowledge on having fixed this or that issue.

Cooljay has done as much or more as anyone. DoktorBert is a working tech and knows the system well - but he sold his diesel a while back and is MIA from this forum.

Suggestions:

- Send an email through the private messaging system to DoktorBert.
- ask the question on Benzworld.
- As a prospective customer, which technically you are, contact George Murphy and ask. George isn't the technical guru he makes himself out to be in all things, but on ACC II I would trust his response. He was the first to offer a less expensive and more reliable alternative to the dealer part for the servo.

My $0.02 is that, unfortunately, if Mercedes is still selling under two part numbers for the different chassis, there is a difference. Generally I have found they merge or supercede identical or nearly identical parts that were numbered differently but can be interchanged, as the cars get older.

treetrimmer · #12 05-19-2014, 05:35 PM

Thanks a lot, do appreciate all responses on my thread. I may not need to worry about it right now because the used one I'm looking at is actually the w116 part# after all.

Graplr · #13 05-19-2014, 09:11 PM

To the best of my memory the 116 and 123 servos are identical except the mounting location and likely the mounting bracket (not the mounting holes on the servo).

I gave my 116 servo away before I picked up my 79 wagon so I couldn't compare them directly.

I had always assumed the electrical "upgrades" were good deals. I have had no personal experience with them but you say they are junk? What is so bad about them? I almost pulled the trigger on one on eBay a couple years back.

I've been through 3 servos. All were used and all leaked in under a few thousand miles. One plastic and two aluminum. Maybe I have really bad luck? One was shaped a bit different (shorter) so perhaps one was a 116 servo? Either way they all hooked up the same. I finally just bypassed the coolant flow from the servo and put a ball valve in there in case I need heat (I only drive my wagon in the summer). I just keep it closed in the summer.

If it didn't leak so darn much I would agree that it is a good system. Plus I am in the middle of swapping in a turbo engine from an 81 TD and am considering doing a full climate control swap as well.

treetrimmer · #14 05-20-2014, 02:45 AM

I have not personally tried the aluminum ones but I'm going by the experience of an independent MB shop owner whose word I trust completely. He will not install them because he needs to stand behind and warranty all of his work and has seen too many fail prematurely. Factory units only.

The electronic hack solution was in my car until I ripped it out recently. It has never worked, at all, since I bought the car and I cannot see how it ever would from the jury-rigged way that it bypasses the factory system while still using some of the key components like the dash control. I guess I understand how it's supposed to work but it did not.

When is a Mercedes-Benz not a Mercedes-Benz anymore? My answer would be once it gets old and cheap enough to fall into the hands of someone who cannot maintain it properly and factory parts are replaced by horrible aftermarket "solutions" that ironically cost more than the correct parts in some cases. The ACC 2 system is not at all complicated from a repair/maintenance POV but the servos wear out and they are expensive. The solution is a good used part if necessary, not some hack that's guaranteed not to work.

My car came with a thick folder full of receipts showing that the poor lady who owned it before me paid some dipschit scumbag MB shop a ridiculous amount of $$ to "fix" her climate control. All she ever needed was a servo unit but they replaced every other component including the push button control on the dash, (these absolutely never go bad unless you take a hammer to them), two different supposed new servos, (the electronic garbage was on the car when I bought it), and on and on because they did not know the first thing about diagnosing the system. I have access to the factory manual on ACC for 116s and it's all laid out in pretty simple terms for technicians. I guess if you don't have the book, you just guess or ask other morons on the phone or online who also do not have the book and should not go near the cars.

That's the end of my rant. Just because I can buy an old Benz with a quarter million miles for peanuts does not mean that I can repair it like it's an '87 Chevy Citation with parts from Autozone. It does not work out well.

cooljjay · #15 05-20-2014, 04:05 AM

Don't switch in a good amplifier until you check the aux water pump!!!

I blew one that way.

The main thing, besides a leaking servo that kills the system is the aux water pump....it freezes and then in fries the amplifier, the aux pump was never fused and it should have been. Even on the later models it was never fused. A member even sells a quick connect type fuse.

The unwired kit, its not worth the money, as was said above. The man reason I wouldn't consider one, is that it does not control the fresh air flap, meaning the system will circulate the cabin air only.