Fixed VDO 461 Cruise Control Module

[targa80]

Originally Posted by rokemester

You are a brave and smart man!! I’m guessing you have an engineering background.

40 years in the Aerospace industry specializing in main frame computer systems installation, maintenance and repair. The repairs on many occasions went down to the component depending on the system and the technical information available.

[Nick Triesch]

You can also find a used one on eBay. I did for $65 and it works great! I think other brands of cars used this same control unit.

[rokemester]

I knew it!! Engineer all the way��

[rokemester]

Originally Posted by targa80

40 years in the Aerospace industry specializing in main frame computer systems installation, maintenance and repair. The repairs on many occasions went down to the component depending on the system and the technical information available.

Pat, what do you think it would take to build a CC brain with modern electric/computer components? I’m sure you’ve considered the possibility. Not worth the development time I suppose.

Mike

[mysocal911]

Originally Posted by rokemester

Pat, what do you think it would take to build a CC brain with modern electric/computer components? I’m sure you’ve considered the possibility. Not worth the development time I suppose.

Mike

What are "modern electric/computer components" other than a microcontroller chip? Remember, electronic systems today still use; ICs, capacitors, resistors,
transistors, diodes, and relays.

[alexandervdr]

I could get the Cruise Control back to work bij changing the 3 capacitors as described earlier in this thread.
However , 2 problems remain:

1. When setting the speed, say at 80mph, speed immediately drops some 8mph after releasing accelerator pedal and then CC kicks in and holds indefinitely on 72mph. Does this at any speed. Same when using the CC lever to go to a higher speed, I get immediate response, but as soon as I release it will drop some 8mph before CC settles in. FYI: I did check the servo cable setting and all seems fine (no clearance)

2. the reset function does not work.

Anny suggestions where to look ?

[alexandervdr]

as a sequel to my previous post, replacing the 2 ICs (voltage comparators LM2901N) solved all remaining problems.

I noticed these ICs are mentioned 'no longer available' on many sites, I found them here digikey.be/products/nl?keywords=LM2901N%2FNOPB

That is a bit more fiddly than replacing the condensors. Using desoldering copper braid is the trick here to absorb all the solder from the IC legs. Took me not more than an hour including removing and putting back the unit in the car.

For longer distances on highway the cruise control is really nice to have, even in a Porsche.

[mysocal911]

Originally Posted by alexandervdr

as a sequel to my previous post, replacing the 2 ICs (voltage comparators LM2901N) solved all remaining problems.

It's very unlikely that "2 ICs" were the actual problems, as they rarely if ever fail!
Most likely just re-soldering in those areas fixed the problem, i.e. just re-soldering the board typically
fixes the unit without replacing any components.

[uwanna]

Originally Posted by mysocal911

It's very unlikely that "2 ICs" were the actual problems, as they rarely if ever fail!
Most likely just re-soldering in those areas fixed the problem, i.e. just re-soldering the board typically
fixes the unit without replacing any components.

I agree with Loren, I have "fixed", and made operational six bad units by merely
resoldering every connection on the board. Very tedious, but it usually works.

[alexandervdr]

Originally Posted by mysocal911

It's very unlikely that "2 ICs" were the actual problems, as they rarely if ever fail!
Most likely just re-soldering in those areas fixed the problem, i.e. just re-soldering the board typically
fixes the unit without replacing any components.

that may be true, I have some electronics background and it is indeed rather rare that these ICs fail. I knew this bad joint problem existed. I checked before replacing with magnifying glasses, and could not identify any bad solder spot. Whatever it is, the ICs cost me 3$ for the pair, so that is not a big loss.

I could have taken the intermediate step of re-soldering the existing chips.

Whatever, CC works great now