[Vwdiesel] Cruise control on a diesel

[HWY9FERGS@cs.com]

In a message dated 9/20/2005 8:06:24 AM Pacific Daylight Time, Miser writes: 
> How does cruise control work on a diesel? Can I make one? 
> Roooogggger!
> Miser
You're probably wondering what they do for a speed input.  The 85 Jetta (RIP) 
has a set of magnets on the halfshaft hub. I think this may have been stock, 
because the controls were on a stock looking turn signal stalk. Anyway, the 
magnets' fields get picked up by a little coil sensor mounted adjacent to them.  
 Lots of aftermarket CC's did this, even for gas cars. They put them on the 
drive shaft or wherever.  Later models didn't seem to use the magnets.  The VW 
and other diesels came with a W terminal on the alternator which can be used 
either for a ignition signal substitute, or for a tach, or both I suppose, but 
now that I think of it, the 85 has W terminal and a tach, so maybe the W 
terminal can't handle feeding both, thus the magnets.  Anyhow,  in summation, an 
aftermarket unit with magnets will work in any case, but if the unit needs a gas 
car ignition input, you would do best to have an alt with the W terminal.  I 
can imagine also that some of the magnet style units might find the signal 
from the W terminal usable, but I can't be held responsible for damage due to 
improper/misbehaving electrons.   I trust this has been sufficiently confusing.  
Ferg