An interesting partial solution to my Quattro Switch problem

[Tyson Varosyan]

After emailing the list almost a week ago about my Quattro switch not
working on the '86 4kcsq, I have looked over everything that people had to
say. Armed with a jack and a vacuum pump I began to tare into the car.

I found the rear diff switch arm, it moved freely.

I went on to tearing apart the switch. The system is still a bit enigmatic
for me, but I got the general layout of things. I found the lines going to
each diff and tested them. One center diff line (blue) and one rear diff
line (red) held vacuum, which seemed normal. I assume that the Green and
Yellow are pressure relieve lines.

I then went on to the white line going to the engine manifold. This part was
a PITA! I started the engine and noted no vacuum coming from the white hose.
After staring at the diagram under the hood for about 20 minutes, I
concluded that it did not reflect the vacuum line layout on my car. It was
close, but I could not figure out where the Quattro switch line originated
from. I went on to tracing every vacuum connection coming from behind the
firewall. It was hard to test because I was alone and didn't have anyone to
verify the line on the other end. After some torment, I used water and my
first guess was correct. Line located!

Plugging the line on one end resulted in sustained vacuum on the other. I
continued down the mess of T connections tracing everything for leaks. I
have no idea why so much stuff is ran from a single tap on the manifold, but
it is... To my amazement, all the lines held true. I stood dumbfounded over
my car thinking how on earth am I not getting vacuum when all the lines are
good. After more testing, I systematically rechecked all lines plugged in
any way to the Quattro switch. One of the lines was the vaccum source, in
this case the rubber boot that connects the idle control servo/warm-up
regulator thingy to the manifold post-throttle. On the bottom there is a
hole for a line to tap into and this is where the line held vacuum and
should not have. I should have been able to suck air from this line coming
from the manifold, yet nothing was coming out.

Given the line's proximity to the crank vent, I thought to myself, "grime,
figures." After removing the big rubber hose and giving it a good rubbing
with towel soaked in brake cleaner, I gave it the blow-through test. To my
surprise, the air didn't go anywhere! I shoved a screwdriver in there, BAM
hit rubber inside of the hole.

It would seem that a factory defect, a casting error had not made an actual
hole there and left a thin membrane of rubber between the hose and the
vacuum line tap preventing air flow. A few seconds with a hole punch and a
drill I was able to open a nice airway for the system to breathe. I have no
idea what other stuff (and there is lots) that is tapped into and connected
from that vacuum source, but apparently, none of it had been working until
today. Excited, I put everything back together, verified vacuum flow to the
Quattro switch and snapped everything else back together to go for a drive.

My victory was bittersweet. Although my rear diff locks (I got a light) the
center refuses to light up! When switching from position 1 to position 0, I
can hear quite a bit of vacuum being released at the switch, I am sure there
is vacuum reaching the center diff. I believe that the shifting arm on the
center diff may be stuck. It is also possible that it is switching, but I
just don't have the indicator light come on. Any way I can test wheather the
center diff is locked?

Thanks for all your help guys!

Tyson Varosyan
Technical Manager, Uptime Technical Solutions LLC.
tyson at up-times.com
www.up-times.com
206-715-TECH (8324)

UpTime/OnTime/AnyTime