desertsage

Hello all, I could really use some wisdom after endless troubles attempting to repair my failed cruise control. I seem to have a ghost.

Does anyone have experience with installing an aftermarket cruise control, such as the Rostra Universal, on a B5 with the 2.8L 12 valve engine? Looks like I would have to access the throttle body according to the Rostra tech support person, or engineer a connection to the existing rod on the vacuum actuator. Rostra has no experience with installing their CC unit on an A4 B5.

JohnelP

I was curious if there is extra knowledge on this topic. I was trying to get an old laptop to do the control. I had two topics that i could not figure, and all search didn't go anywhere useful. One was how the speed signal from the instrument cluster was delivered (I assume it is a digital signal, but i did not know the protocol.It should be a simple one, but still... Given the cruise module has a Toshiba x86 processor, I assume there is a lot of logic involved. And second, what was the modulation for the actuator. Voltage controlled? pulse width modulation? ?

Anyway, when shopping a car for my wife, one model didn't have cruise control, and dealer gave me a long list of companies to do aftermarket cruise control approved by dealers.

desertsage

I discussed this with a tech from MNR (M+R?) electronics, who is an authorized seller for the Rostra system. He has worked there since the 90s and had no experience with installing the Rostra Cruise in an Audi A4, B5. After letting him know that I have researched the VSS signal wire location and color (blue and white) the tech said that it should work fine if a cable connection to the throttle can be engineered. I'm pretty confident that I will be able to connect the Rostra cable to the threaded rod on the existing vacuum actuator. Anyway, I just purchased the system from them along with a stalk switch. The tech said that I could probably use the existing Audi stalk switch as the wiring would be compatible (he looked at the wiring schematic) but since that Audi switch is problematic I opted for a Rostra switch. Rostra also says that if you use a switch other than theirs, it will void the warranty, so kind of a conflict there. I will update after I get it installed.

JohnelP

I hope you are familiar with these two links already. I think those are the best I could find so far:
https://www.oschmid.ch/mt/a4-tempomat/a4-tempomat.php (schema is at the end of the page)
https://forums.vwvortex.com/showthre...t-any-interest

desertsage

Hello and thank you! I may have seen that info in the past. I did re-solder my module the first time it failed. That lasted for quite awhile before failing again. I then bought a reconditioned unit on eBay for $50 which didn't work but the seller replaced it for me. The replacement is still functioning (I believe) as it's not dropping out completely like it had prior to replacing the modules in the past. The symptoms the cruise is exhibiting now went from a slow decrease in speed when set to gradually failing altogether. I thought that it must be a vacuum leak so replaced hoses, the vacuum pump, rebuilt the pedal switches, checked for vacuum leaks and had none that I could tell. No vacuum leaks in the pedal switches and electrical continuity is good. It's possible that the module has failed again with different symptoms. I'm getting weary of repairing this system and thought I would try the aftermarket electric type that doesn't rely on vacuum.

It has yet to arrive but I will def post here after I get it up and running (hopefully!). Oh, FYI. I did re-solder the module connections on the IC board but without results this time. I think it's still working?