VDO cc brains are often similar,internally.
If memory helps me,diodes are not so much and can rarely fail.There are , in the middle(I am struggling with memory) at least 2 electrolithic condenser, very weak.change them.
Then there are 2 ICs ,LM 2901, they are not really reliable when they're 20+ years old, and when you reflow solder joints they can perish , they cannot stand the heat(one of the problems when you put this pcb in an oven or you insist with your electric solder on the joints...
For piece of mind I will replace electrolithic condenser and those ICs,when I found them in a pcb, like I did to my GTS cooling fans ECU.
I 'd start from those componnts.

 

I forgot tantalium condensers!


here's the picture
with numbered condensers i'dchange.
1 = 15uF 10V Tantal 2 = 2,2uF 35V Tantal 3 = 1,5uF 25V Tantal 4 = 10uF 16V Tantal

5 = 2,2uF 35V Tantal 6 = 4,7uF 10V Tantal 7 = 47uF 16V Standard 8 = 47uF 16V Standard


from sternzeit-107.de

 

Great - thanks Scott - this will be interesting..

Alan

 

By condenser you mean capacitor, correct?

 

I think it makes sense to replace electrolytic capacitors preventatively, Tantalum capacitors are normally very reliable with limited wearout mechanisms and good temperature tolerance. If a tantalum capacitor fails it is by far most likely to go SC due to overvoltage oxide stressing - so is easily tested in situ with an ohmmeter. I'd not take the step of replacing all these unless they test bad...

Alan

 

Yep, but I experienced bad values Sometime... Change capacitors, ICs and diodes for pennies, so there's nothing prone to fail...

 

I think we need to add early/late to the poll, 928 Int'l lists two different part numbers: 928 617 127 00 for '78-87 and 911 617 227 00 for '88-95.

Now what is interesting is that the '78-87 part is also available rebuilt for $395 (core req'd), while the '88-95 is only available new for a lot of money, or used for dirt-cheap ($100). My kindergarten economics education tells me that this is likely a supply-demand issue for the later boxes, lots of supply and no one needs one...

We're 3-for-3 with later cars (88, 90, 93), all working and never a sign of any problems. Of the folks who have reported problems, how many were '78-87 versus 88-95?

The advice to replace the caps is good, electrolytics in particular get dried out and lose effectiveness-- which can lead to intermittent problems. Those are usually can-shaped and commonly used for filtering the 12v power bus.

 

88 plus is rarely an issue and the brain is used on a lot of different cars. As Jim says $100 on eBay and problem solved if there was a problem with the brain in the first place.

The early brain 78 to 87 is the major culprit. There is a company on eBay that sells refurbished brains and I used to buy from them for resale at about $90 each. Problem was that two out of three would give trouble so I stopped. This brain is used on the 78 to 87 911 series as well - wonder what they do for a fix?

 

I could easily program one of these arduino micro's and lay out a board to replace the cruise control unit in a few days if someone gets the needed data. The C++ code would be simple after the last item I'm just finishing programming. You will get to see that soon btw
The total unit would be about the size of a pack of cigarettes and sell for well under $150 easy.

 

My '88 works fine with over 200k on the clock... but I have to accelerate past the point I want and it 'settles' to the correct speed. Other than that minor quirk -no problems! (knock on wood)

 

Mine's worked reliably for as long as I've owned the car.

On it's maiden voyage for me, a Denver to Los Angeles cruise, I ended up spending a good half an hour in a burger stand parking lot. Sipping a drink and rolling through the owners manual again to get a better handle on the cruise function. I needed it not because I was lazy, but to help keep speed down closer to the posted limit. It just wanted to go faster all the time, and it was so effortless the speed would creep up without me noticing. Leaving the stop and headed west again on I-70, nice long straight uphill on-ramp. Bwwwahhhh! Before the top, a shadow from a low-flying plane passed over the hood. Seconds later the radar detector sprang to life, but I was already back to sub-sonic velocity. Top the ridge and there's a row of Colorado's finest, kined up and ready for a le Mans-style start. I -really- needed that cruise to work for most of the rest of that first ride home.

 

To one of the mods- is it possible to change the polls? Seems like there needs to be two polls:

Does your '78 - '87 cruise control work?
a) yes
b) no
c) intermittently
d) don't own a '78-'87

Does your '88 - '95 cruise control work?
a) yes
b) no
c) intermittently
d) don't own an '88-'95

 

Sounds like too much slack in the Bowden cable that connects the cruise-control actuator to bellcrank assemble. It is adjustable at the bellcrank, you want just a bit of slack.

Cheers, Jim

 

Cruise control in the GTS works fine, though 'RESUME' in the powerband of 3rd gear is pretty amusing.....

 

justone question:
can someone provides me the VDO part numbers pressed on the alluminium case?