SeanR

Been working on some cruise control brains that Roger had on hand and all of them are bad. Figured I'd take them apart and see what I can find as they don't work anyway and maybe I can learn something.

These three are all the same external part number and going from left to right. All are part number 928 617 127 00. They all click with the key on showing they have power entering the unit, and all click off when turned off but the failures are all different.

Far left will accelerate when when you push the cruise stalk forward but won't maintain speed. No obvious hot spots.

Middle won't work on any function but found two burnt resistors that I'm sure I can replace.

Right one will accelerate as soon as you push the stalk forward, and continues until you hit the brake pedal or turn it off. No visual burnt things.

We've sent off a few to be rebuilt and they always come back with the same issues and the only ones that have worked as they should are the ones from Mark at 928 International. Marks guy has it figured out so if you need one, talk to him. I'm just playing with these.

Just thoughts for the community.

jwillman

Mine has the far left units symptoms - accelerates when stalk is pushed forward and then nothing else when released. its on my to do list

Watching with great interest!

SMTCapeCod

The one on the left is rigged/configured differently? (looking at two adjacent cylinders on the mid and right panels, and the positioning of the resistors. Are there build date stamps, given they are same part no.?

a4sfed928

These could be repaired easily if the two ICs are not proprietary.

a4sfed928

Large discrete components definitely look like circuits of antiquity from my time.

outbackgeorgia

Those electrolytics have probably dried out by now
Dave

oldfrat

Sure glad I didn't need one of those! Many thanks for working your magic to get mine working again. It is a great pleasure drive the car after your work!

Brad

Adk46

Yes, that's been my impression, that electrolytic capacitors have the least longevity of any component.

About ten years ago, these things started to fail in all sorts of relatively new devices, such as a few of my wifi routers. Chinese manufacturers had gotten hold of a stolen formula for the electrolyte, but the formula left out a critical ingredient.

Don Carter

Sean,

I have a few of these laying around too and would like to get one going for my 86. Interesting observation about the 928Intl rebuilds. I hadn't heard that before. There was a thread a month or so ago where several people named rebuilders that did a good job on their brains, and I meant to send one of mine off to one of those rebuilders but never got around to it.

WallyP

Back in the late '80's or early '90's, one of the top-rated Japanese electronic firms had a large run of "faulty" capacitors. They lasted for about fifteen years, then failed. I had to replace several on the Bose audio system in Lynn's STS.

siscogts

Condensers made by frako, usually 100uF and 16volts.. Start to replace them, then change blown resistors. After that, I have 2 more steps for far left and far right:relais near pin plugs then ics... Usually have something like lm2901... They last forever but sometimes changing them is useful.

Lizard928

Resolder every solder joint and replace any capacitors, that brings 99.99% of them back to life.

hacker-pschorr

That's the issue with our 87.

I wasn't even aware Mark (or anyone) was rebuilding these. I was going to try the toaster oven trick.

Alan

16V specs are too low for this application (use 25V +). It is shocking to see the quantity of discrete components in these controllers - even for this timeframe I'm surprised they did not achieve a much better integrated controller - after all it really doesn't actually do all that much... (And these ones do even less...)

Alan

John Speake

The ICs are standard parts... the tricky component to source is the MOSFET .