[200q20v] How do I stop the 15MPH cutout for the center dif?

hah at srv.net hah at srv.net
Mon Nov 27 15:52:00 EST 2000

>How about this...
>Connect the rear diff-lock actuator to vacuum via a solenoid-switch. Rig 
>solenoid to the WFO throttle switch such that the rear diff locks
>automatically at WFO and un-locks automatically when off-WFO. Insert a
>toggle-switch in series as an enable/disable switch.

But the 3B has only an idle switch & throttle position potentiometer, no 
actual WFO switch - doh!

How about: rig up a separate vacuum reservoir (don't want diff locks to 
mess with climate control!) with appropriate check valves. Obtain from 
favorite Rube Goldberg shop one (1) pressure-activated NO switch contact - 
adjustable for triggering pressure of course; and one (1) vacuum solenoid 
(spare GM CC programmer, anyone). T pressure switch into analog boost gauge 
line (of course you have one) and wire the ground side of vacuum solenoid's 
coil through it. Supply vacuum from separate reservoir through solenoid to 
diff lock actuator, sprinkle liberally with check valves to isolate factory 
switch operation from kludged operation, and begin adjusting boost-lockup 
threshold. Voila!

Hmm, is it bad for diff locks to engage when one wheel is already spinning? 
Crunch! Better set that threshold at 0.7 bar where there isn't much 
torque...might even work on a N/A 5k/100q then, whee what fun.

If all you have is a spare GM CC programmer and no Rube Goldberg shop 
nearby (or no McMaster-Carr catalog), try a random SPST toggle in place of 
the pressure switch, not quite as interesting tho.

HTH (right!)
Henry Harper
1991 200 quattro, 111k, need to swap cars before I get in trouble, 
surprised I didn't get a ticket this morning after showing >2 bar to a 
pickup that thought I started from the traffic signal too slow and tried to 
go around and splash me, next car coming the other way was a deputy (on his 
way to work with radar off apparently), as I casually coasted down from ~85 
in a 55 so as to not run over the old-Bug who used to be quite a ways in 
1988 GTI 16v, 215k, feeling neglected as I've been driving the big car for 
almost two weeks, not so fun up the ski hill but doesn't cost $30-for-20mpg 
to fill up either

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