A call for help with ACCII - PeachParts Mercedes-Benz Forum

Phillytwotank · #1 06-30-2014, 11:36 PM

After years of trouble shooting and repairs of my ACCII in the el toro I feel like I've got a great grasp on all of that.

However, with the ACCIII in the blues mobile I feel a little like a babe in the woods. '84 w123

Moms is driving the car to work three days a week and she was super excited to have the climate control fully operational with cold AC.

Since I've had the car everything with the climate control had been working fine. I just charged up the refrigerant last weekend and it was ALL working fine all week until Friday.

So here's the situation...

No Blower in any mode,I can feel the compressor kick on, fuse 8 is good, no voltage at the blower, no vacuum pods are moving.

I took apart the pbu and checked for broken solder joints and didn't see anything a miss. My first time taking one apart tho so I'm not 100% positive I can say that it was all good.

Can anybody please maybe point me in a direction towards something to do next? I don't really want to start throwing parts at it if I can somehow narrow in on the exact cause of the problem.

Got to get it working again for me mom.

Thanks.
P

uberwasser · #2 07-01-2014, 12:08 AM

When I had this exact same symptom, it was the temperature regulator. The silver box behind the glove box.

You can pull junkyard spares from either a W123 or a W126. In the W126 they are located down behind the kickpanel near the blower, instead of behind the glove box.

Here is a site that covers some diagnostic steps:

http://userweb.windwireless.net/~jimc/mamerepairs.html#acctest

*Edit* Crud. The site is down. It was working just a month or two ago. Hopefully it comes back. If/when it does I'll copy it all to another document - hopefully it's not lost forever

Anyway, without that resource what I'd suggest instead is to review the FSM section on climate control troubleshooting. It's a decent resource.

You can also do a visual check of your blower resistor, the toaster coil filled item up behind the passenger headlight. Look for any broken/burnt wires.

And when you have your glovebox liner out you should check and replace, if needed, the foam hose for the temp sensor along the underside of the dash. I used a PVC hose, I think 1/2" ID. Nice snug fit, and will never deteriorate like the foam did.

Phillytwotank · #3 07-01-2014, 06:55 AM

Thanks for the tip. I have inspected the blower resistor and replaced the temp hose.

I've heard of this temp regulator box you speak of. Is there any way to test that independently from the rest of the system?

I'll grab a spare first chance I get.

uberwasser · #4 07-01-2014, 11:13 AM

I haven't seen much in the way of diagnostic info for this part. It's somewhat a complex item, for its time. It handles most of the logic in the system - it takes input from the cabin sensor regarding current temp, monitors blower speed, monovalve state, and the input from the driver as to what condition they want in the cabin (temp wheel selection, fan speed selection, etc) and sends commands to the various parts to adjust everything accordingly.

You might get some idea of what it should be doing by studying the wiring diagram for the system. Click this link, save the image, then you can zoom in:

http://i.imgur.com/boj8wly.jpg

Then check the FSM. Like I said, it has some methods for testing the system and suggestions on what the replace if it behaves in certain ways. Unfortunately some of these tests require a testing tool that is designed to report pass/fail, rather than using something more standard like a voltmeter with expected readings noted. That was where the page I linked above came in - that person recorded a variety of tests that can be performed, which pins to test and jump, etc on the push button that lead to a pretty good diagnostic guide. Like I said, hopefully it's just down temporarily.

uberwasser · #5 07-01-2014, 11:18 AM

Forgot to mention -

Obviously there are ways to test and repair this item. Programa sells refurbished ones with a warranty. But the DIY community hasn't cracked the nut yet, as far as I know.

The only person I know who is probably trying is JamesDean. He posted pictures a while back of the temp regulator and the blower relay opened up for inspection.

If I remember right one of the challenges is that the board has some integrated circuits. That raises the complexity quite a bit.

Anyway, it may be worth shooting him a PM to see if he has any insight, or has made any progress on that.

Maxbumpo · #6 07-01-2014, 11:53 AM

Quote:

Originally Posted by uberwasser

When I had this exact same symptom, it was the temperature regulator. The silver box behind the glove box.

You can pull junkyard spares from either a W123 or a W126. In the W126 they are located down behind the kickpanel near the blower, instead of behind the glove box.

Here is a site that covers some diagnostic steps:

http://userweb.windwireless.net/~jimc/mamerepairs.html#acctest

*Edit* Crud. The site is down. It was working just a month or two ago. Hopefully it comes back. If/when it does I'll copy it all to another document - hopefully it's not lost forever

Here is the replacement website:
Middle-aged Mercedes Electrical Repairs

uberwasser · #7 07-01-2014, 12:37 PM

Much appreciated.

Phillytwotank · #8 07-07-2014, 12:59 PM

some helpful info. Thanks.

I'm narrowing in on the PBU. I took it out again and while holding it in my hands, squeezed a bit and everything came to life for a brief moment. Then i couldn't get it to do it again.

Like i said.. i took it apart already and didn't see any obvious burn spots or broken solder.

I'll just swap another one in there if i can find one easy.

WTB: good ACCIII '84w123 climate control push button unit!!

There is a w123 at the pull a part in charlotte if i ever get a chance to get up there before it gets gone.

vstech · #9 07-07-2014, 06:30 PM

I saw this post and wondered what computer text language was being discussed..

http://en.wikipedia.org/wiki/ASCII

Phillytwotank · #10 07-07-2014, 07:48 PM

WoW! My brain just shivered a lil bit from trying to understand ASCII

I actually miss "spelled" the title of my thread. Should have read "ACCIII" as in the last version of the w123 auto climate control.

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