Whitesands

Add to the poll?

"Working but would like a spare"

FLYVMO

SISCOGTS:

928.617.127.00 MFG date 11/79 also stamped with 412.203/1/10
928.617.127.00 MFG date 9/86 also stamped with 412.203/1/10

White Lightnin'

Thanks Jim!

The Fixer

Scott you can have my CC brain, (found it in a box of removed stuff) no need for it in the RS. I don't know if it works, IIRC my cruise was not working when i bought the car with 57K miles. I never looked into why as i didn't care or want to use it so not sure on condition. The car was very well kept though so it may work.

siscogts

Thank you, checked Yesterday night my gts CC brain, it is 911.617 227 00,

but i believe that internalPCB should be the same, almost.

IMHO,it's not impossible to have these brains perfectly refurbished, unless the big IC inside(late systems of VDO cruise control brain) is gone,it was made on purpose for VDO and it is actually impossible to get.the rest is imho really basic.

I saved my cooling fans brain with 5,50 euro,and 3 euro for the mosfet amp .... this CC brain is far better and less complicated....

svpmx83

Motorola manufactured a single chip cruise IC for vacuum controlled systems that would work as an alternative if you can find them.

The datasheet on the chip contains control strategy info for anyone looking to build/program a microcontroller replacement
MC14460

an alternative (I'm currently part way through) would be to replace the whole thing with a GM Delphi module
http://chevythunder.com/cruise_control_system.htm

syoo8

Oooh! How difficult would this be to retrofit to our cars?

siscogts

that's great information!thank you for the datasheet!
changing to a chevy brain?not abad idea,but I still prefer to keep the original and work on it, maybe using plastik 70 to protect the board..

The Forgotten On

If some one could make a guide and parts list to properly replace known problem part that fail that would be amazing and the easier option.

I some one managed to get a newer style and more reliable system to work in their 928 that would give many people a new option to work with.

i can't wait to see where this thread goes.

UpFixenDerPorsche

In answer to your question: Yes.

But now a question re your question: OMG why would want it ???

IMHO (ok ok ... not much 'H' ...) cruise control is for the totally lame and mentally inane nimcompoop drivers infesting highways everywhere.!!! Arrrggghhh.!

As if we're not sufficiently 'brain-dead' already. :-[

I think cruise control is a full-on next-to-dangerous *$@??>*))% that should be banned.

I've disconnected the CC's on both my 928's, and fortunately none of my other vehicles have it.

If you're a driver who is sensitive to ever-changing road conditions and one who is always reading the road ahead this dang thing will drive you mad as it's always doing it's thing according to the rise and fall of the road, whereas mentally you might be reacting quite differently to what you see ahead: so who you gonna trust eh?

Or are you going to turn off your brain and let the CC rear-end an 18 wheeler at 60?

Sheesh.

.

Fogey1

IMO, Cruise Control ≠ Brain Dead - particularly in areas infested with revenuers (excuse me; armed safety professionals). And, as a CC user who sets at ~ 8-10mph above the speed limit on interstates and occasionally as low as 35 on lightly traveled but heavily enforced municipal highways, I can state categorically that the accordion drivers are less attentive and a greater hindrance to smooth traffic flow than I. CC is also helpful in reducing fatigue over lightly trafficked long distances where driving at a comfortable speed exposes one to a high risk of enforcement action. I use CC, when I do, in preference to falling asleep at the speed limit, jacking my stress levels to 11 or being jailed by an angry cop.

That said, the finest CC I have ever used was in my 1995 Chevrolet Caprice former cop car with a certified digital speedometer. It was dead-on constant once set, whether at 35 or 105, up hill and down dale, and a single tap up or down on the stalk changed that speed by 1mph up or down. Two taps 2mph, and so forth. Big torquey LT1 V-8 was a great help in this precision, of course, but it was _much_ better than my Dad's same year 740, which was awful, or the non-op system in my 928.

jcorenman

Oh, that. ... That's why they invented "adaptive cruise control", so that you can safely turn off your brain and not rear-end a semi at 60... another example of successfully replacing common sense with technology.



Actually I completely agree with you, and we rarely use CC (in spite of ours all working).

There are two circumstances where it can sometimes be useful:
1) You've got a weak radar source somewhere ahead and you need to artificially match your speed to some arbitrary number on a sign; and
2) Ohio.

I'm joking about the second, and the first is way off-topic. But we almost never use the CC and instead just drive at a reasonable speed for whatever the road conditions are at the moment.
Occasionally that leads to a roadside conversation on that topic, but that's just one of the many road hazards that you have to watch for.

I think the real answer is a simple desire that all of the systems in the car work as intended. And that's perfectly reasonable, even if they are largely unused.

The stock CC brain does a good job when it works, and the troubles are for the most part just flaky solder joints which can be fixed, or ordinary parts which can be replaced.
So instead of designing a new one and throwing away the broken unit, why not just fix it?
Modern car repair consists of throwing away questionable parts until the car runs, no one fixes anything. But why not?? Isn't fixing stuff what this group is all about?

Cheers, Jim

syoo8

I'll tell you why I would want it: my health.

I use my 928 as a grand-tourer in the most literal sense of the word. Every summer, there are at least 3-4 days where I drive it all day- meaning, I drive it for as long as I can, then pull over to a motel.

The constant pressure that my right foot has to put on the accelerator does a number on my body. I am not a professional driver, so my body is not used to it. I can feel the effects of driving for long distances without cruise control for at least a week after I've done it. Not so with cruise control.

It doesn't have so much to do with being brain-dead, as it does trying to avoid sciatica. That has a big affect on my profession, and I can't afford to have it.

syoo8

Exactly. When I bought my '86.5 the sunroof, central locking, cruise control, rear hatch and HVAC were all inoperable. Would be fun to get the tempostat working. Avoiding sciatica is great too.

This feels odd to disagree with you Jim, but here it goes. :-)

We actually throw away broken things on the car all the time- things that can be refurbished with some rubber bits and a little work. Clutch slave comes to mind: they can be refurbished, but many get a new one to refresh, for example. Ditto for electric window motors.

As I wrote in the original post, I have two tempostats in my two cars: (only one working) plus five non-working units. (I only have three in the garage, because two I threw away in the garbage after attempting solder reflow.) That's six non-working units in my six years of 928 ownership. I've not encountered anything else so unreliable in 928 ownership. I think it might be time for some different options.

LT Texan

Same for my '78. Settles 3 or 4 mph under the set speed.