[Urq] Re: Diff. lock switch conversion for '83 Ur Q

[QSHIPQ at aol.com]

I did the dual rear controller method on my 83.   For install pics, see
http://www.hometown.aol.com/qshipq/page1.html

I did my install per the factory.  Per the factory means the diff lock 'box' 
and switch backlight, become 'on- standby' when the car is on, and shut off 
when the car is off.  In 'on' mode the vacuum is in the default position of 
"diff unlock", IOW, the vacuum defaults to inlet (feed) to outlet (diff unlock).  
All rear diff cars with electronic locking are wired this way.  My comments on 
"overheat" only applied to when the diff is activated, IOW when the relay in 
the control box has now triggered inlet(feed) to outlet(diff locked).  There 
is a cooling air port on the control box, and there is a thermal shutdown for 
the box (it doesn't turn off, it only turns the diff to unlock, box goes back 
to standby).  I think it's where you place the box, since in my install (behind 
glove box), I ran 16 hours continuous with the center diff locked to 
Steamboat one year as a test.  Never a shutdown.

There are 2 power feeds to the box, 1 is to activate, the other is diff 
lock/unlock.  The diff lock/unlock is 12v on, 12v off momentary contact.  The 
standby is continuous on (with car), and full shutdown (with car - full shutdown 
means if you have the diff locked and you shut the car off, the diffs are 
unlocked next time you start car).  The triangle turns on with intention, the actual 
diff lock light turns on only when the diff is actually engaged.

WRT window switches then, you can certainly trigger the diff activation with 
one, but you really only need one side hooked up to it.  Any momentary contact 
12v switch or button will work.  To actually turn off and on the box?  I 
wouldn't, audi turns them on when the ignition is on.

HTH

Scott "diff controller box nerd" Justusson
'84 urq
'83 urq





In a message dated 11/21/2003 7:25:03 PM Central Standard Time, 
Steven.Buchholz at kla-tencor.com writes:
... let me get this straight ... you power down the diff lock control
modules???  Do you know whether they are guaranteed to remain in one
position with no power applied?  ISTR Justusson reporting that these
controllers get hot too ... and I have a fuzzy recollection that he thought
it was due to the speed signals not changing ... but I'm probably
oversimplifying.  Are you sure you have things wired correctly?  Window
switches are not as simple in operation as a general DPDT switch, on each
pole there is one contact that is closed even when the switch is in the
middle position ... if you were using this connection you might well be
acting as though the momentary contact lock/unlock switch that the module
normally works with is always pushed ... which might then cause it to draw
excess current.  Given what can happen if a diff is locked or unlocked
unexpectedly at the wrong time, I would certainly prefer to have a system
that is always powered up ...