4WD Light Doesn't Work / Blue Vacuum Hose

>If someone has an 88-90 YJ and wouldn't mind looking under
>the battery tray and telling me where the blue hose hooks, I
>would sure appreciate it.

That "blue hose" is part of the vacuum harness for the front
axle disconnect system.  Being as anal as I am, (all hoses
must be accounted for), I to wondered what function did that
"blue hose" perform.

The vacuum harness, (which I had to replace), runs between
the front axle, the firewall mounted vacuum switch and the
Tcase, (if you look on top of the xfer case you will find
where the harness ends, and the "blue hose".

At the end of the "blue hose", (the end in question/under
the battery) there should be a small plastic disk about the
same size as a $.50 piece, and approx .25in thick with a
nipple on each end, (mine appears to be 2 halves glued
together white/black).

This disk is a "one way" release valve. Whatever you do
don't plug it up with gasket sealer otherwise your axle
won't engage and you will be forced to purchase the whole
harness when you "puncture it" trying to get all that goop
back out...8(.

Unfortunately you must purchase the whole harness in order
to get the valve, wasn't bad under $20. The whole
installation including removal took about .5 hour.

- author unknown (but an excellent bit of info!)

(This may resolve those cases where the 4WD Light doesn't
come on - lars)