syoo8

Hi everyone,

Perhaps this is a naïve idea, but I wanted to throw it out there after reading this very interesting thread.

I've been through 7 cruise control brains between my two 928s, and only one of them works properly.

I've tried the solder method (twice) and it hasn't worked for me. (My soldering technique was developed in the eighth grade, then in lab electronics in college- where I barely squeaked by with a B-. I suck at it.)

Perhaps this is a question for Alan Moore, PorKen, or another resident electronics luminary:

How difficult would it be to recreate VDO's cruise control brain, if we got, say, 100 or so people to buy in? Could we 'commission' a small, low-cost computer, with wiring to connect to the VDO wiring harness- something that would be bulletproof?

(I would be happy to do all of the legwork. This would not be a money-making venture- it would be a 'public service' for the 928 and 911 community.)

Rob Edwards

Have you tried the oven roasting method?

https://rennlist.com/forums/928-foru...-the-oven.html

syoo8

Hi Rob,

I haven't- several on the board have reported that this works- but others have reported that bringing the circuit board to a temperature high enough to reflow the solder also damages components at the same time. Given my luck with electrical components I didn't try it.

My '86 and '87 had inoperative CC brains. I bought three used brains for very cheap from a used parts dealer (not 928Intl) and they didn't work. Then, I bought two "refurbished" units. One sits in the '87 and works. The other sits in the '86 and worked for a while- now it is intermittent, at best.

Buying another refurbished CC brain is possible, as is reflowing the solder with a gun or an oven... but isn't there a better way?

The Forgotten On

If some one could program a Raspberry Pi to take the analog input of the switch and then trip a set of relays that would be great.

Or even use an arduino to make a CC computer. The biggest problem would be the programming because many of us here don't know how to use C++ or other program scripts.

If some one is willing to do this, that would be awesome

FLYVMO

Scott,

These places do reverse engineering (many do I'm sure) so you might want to send one CC to them for an estimate.

http://www.silvercircuits.com/index.htm
http://www.americancircuits.com/aci/...6/Default.aspx

Cheers!
Carl

Niles

I'm definitely interested in this. I hope to hear someone is going to go forward with it.

FreedP

I'm in for 1, maybe 2.

a4sfed928

I do some work on PCBs both through hole and surface mount and the temperature profile for reflow is specific and not just an ordinary oven.
You are correct in the fact that components can be damaged in an ordinary oven. I would suggest not to "reinvent the wheel" but to determine what the failure mode is in the original board and correct this with a design change.
Just my .02

wpgshark

There are other alternatives to solder, that may work.
Electrically conductive glue and epoxy's are used for many applications, many more severe than a circuit board. They have been used for low volume circuit boards but are too expensive when the volume goes up. Ideal if you know which pins are loose or where there is a break in the board.

Something like this, and I have no affiliation

http://www.circuitspecialists.com/8331-14g.html

Lance

syoo8

Hi Lance,

The trouble with reflowing the solder is that you never know which pin is loose. Or, at least, I didn't by visual inspection. That's why you have to go through and spend the two hours to reflow every connection- and not make a mistake.

Alan

I just don't see them as unreliable enough to warrant this. By your own account you are buying risky ones and had poor ones... get a good one and be done with it?

If they were really billed as refurbished - send them back as DOA.

Alan

thezonster

I recently "re-flowed" the cruise brain board from my 86.5 in the oven, and it now works.
Fixed it!

GregBBRD

Certainly a percentage of the brains are going to have "soldering issues".

However, there's going to be a percentage that have component issues.

It's not realistic to think that any one fix is going to fix all the units.

As far as remaking pieces.....Anything can be re-made.

Getting something made for this tiny, tiny market is the problem, so someone generally has to undertake something like this as a "hobby".

syoo8

I defer to your judgement as the resident 928 Electrics expert (and author of the eponymous website/primer.)

However, I must add that almost all of the two dozen or so 928 owners I've physically met do not have a working cruise control. It seems to me that the CC units are indeed quite unreliable, compared to the other systems in the car that seem to work for most people: EZF, LH, etc.

(That might be perception of course: one can "live with" a faulty cruise control, not so much with a bad ECU.)

Thanks Carl for your help- I will contact american circuits and report my findings.

syoo8

This is what is so frustrating to me. With one of my CC "brains" I reflowed the solder, and even got "fancy"- by testing the transistors with a "diode tester" (read: multimeter) to see if any of the transistors were bad. It took hours, the transistors seemed to be "good," and after all of that work, no change.