Cruise control how to, AHU.

vtpsd

Veteran Member
Joined
Aug 15, 2013
Location
Vermont
TDI
03 jsw TDI, audi 90 AHU swap
Todd, cleaning those switches should help. Like I said, my switch wasnt giving any detectable voltage from any of its outputs, and it didnt even look that dirty.

I am now using a mk4 diesel pedal (part number
6Q1 721 503 B) . I never even tried it with the gasoline pedal.
 

ToddA1

Top Post Dawg
Joined
Aug 3, 2011
Location
NJ 08002
TDI
'96 B4V, '97 B4 (sold), '97 Jetta (scrapped)
Well, I finally got around to cleaning out the switch. The tracks on the board didn't look all that bad. The contacts on the 3 position switch weren't too bad either.

What looked bad were the contacts on the "set" button. Nice and green.

Everything got scuffed with a scotchbrite and coated in dielectric grease. I have cruise!

-Todd
 

brokensf

Member
Joined
Dec 5, 2006
Location
san francisco
TDI
1982 AHU TDI Vanagon
I spent some time a few weeks ago wiring up cruise control in my AHU Vanagon. It was working pretty consistently a few days ago. All of the values / checks in measuring block 006 were good. The brake pedal switch I used is a little bit touchy, so it doesn't work every time, but it was good enough.

Yesterday it wouldn't work. Nothing.
Hooked it up to VCDS today and block 006 is saying "ERROR Group 006 Not Available"

It never showed this before. I've tried reactivating cruise control but nothing.

Fault codes:
00741 - Brake Pedal Monitoring 27-10 - implausible Signal - Intermittent
00750 - Warning Lamp 31-10 - Open or Short to Ground - Intermittent
01117 - Generator Terminal DF Load Signal 27-00 - Implausible Signal
00671 - Cruise Control Switch (E45) 25-10 - Unknown Switch Condition - Intermittent

Here's my wiring diagram:


I'm running LED brake lights and have an incandescent brake light bulb wired up to fool the ECU.

I'm stumped because it was working one day, and now it's not even showing up in vcds. I did work on the ECU harness, but I just pulled the split loom back so I could run the CEL wire to the front of the van.

Any idea where to start troubleshooting?
Thanks!
 

G60ING

Top Post Dawg
Joined
Aug 5, 2001
Location
MD
TDI
No TDIs Currently, I have an R36 Corrado. I've had an ALH Corrado swap, AHU Corrado swap and 2003 TDI Jetta
That’s an odd error, you might want to see if you have continuity to the ecu from the switches and so on. I wonder if something shorted out or is chaffed.
 

jimbote

Certified Volkswagen Nut
Joined
Jul 10, 2006
Location
spiral arm, milky way (aka central NC)
TDI
Tacoma 4x4 converted to TDI
Try wiring both your normally closed Clutch and Brake switches straight to 12 volts and leave the normally open brake light switch wire unconnected... this would eliminate any possible switch error
 

brokensf

Member
Joined
Dec 5, 2006
Location
san francisco
TDI
1982 AHU TDI Vanagon
Thanks for the help. Fortunately / unfortunately the problem fixed itself... I definitely need to take a closer look at the wiring.

Cruise worked just fine for 80 miles yesterday! The hyundai brake switch I used is really touchy with a 1mm sweet spot and it shut off after going over a rough section of road twice, but I could turn it right back on.

One thing that I find kind of strange:
I have a scangauge connected to the obdII port. Before the cruise install the glowplug light would flash constantly with the engine running. After adding cruise, the glowplug light turns off as it should. No more flashing. I know it's supposed to flash when VCDS is open, so I'm surprised that adding cruise made any difference with the scangauge hooked up.

I came across this info in another cruise control thread, but it should be posted here too:
Adding cruise fixed the "dead" accelerator pedal issue I was having on startup. When you first start the engine and press the accelerator, it'll crawl forward a little bit but then the pedal will just die and won't give it any more fuel. Letting off the pedal and getting back on it worked every time, so it was more annoying than a real problem.

It's nice to have a normal pedal after a year and a half!
 

brokensf

Member
Joined
Dec 5, 2006
Location
san francisco
TDI
1982 AHU TDI Vanagon
The hyundai brake switch I used is really touchy with a 1mm sweet spot ...
This brake switch is my problem. It wasn't a wiring issue.

I realized that the glow plug light flashing was an indication of "implausible brake signal" or whatever it is that tells the ECU to flash the light. I'd read this somewhere but forgot all about it and reading "NOT INSTALLED" on measuring block 6 seemed a lot more ominous so I thought something major was wrong.

The plunger on the brake pedal switch will stick closed sometimes. Other times it will close too much and the value changes to open again. I'm going to look for a New Beetle switch to replace it next time I'm near a junkyard.

Happy to say that knowing this is the issue I can work around it and get the cruise to activate most of the time.

Got a 2k mile trip to Moab this week and it's sure nice to have cruise on the open road ;)
 
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