Hello Jtarchala,
Interesting (and doubtless very vexing) trouble...
I always recommend that an OWNER beg, borrow or BUY
the FACTORY+WORKSHOP+REPAIR manual..
but as that is not always an option...
I like to point out where
FREE wiring diagrams and
TECHNICAL SERVICE BULLETINS (TSBs) can
be accessed (on
BBB Industries website (registration
is required... as these are real documents))... for popular
USA Market vehicles.
FREE diagrams & TSBs
BBB Industries Premium Alternators Starters Power Steering Products
I noticed the Manual switch (dash) was assumed to be the trouble... out of curiosity I tried looking up your switch...
Please note: while totally UN-SCIENTIFIC.. when I find
multiple BRANDS of a particular switch STILL (plentifully) available ...
I CONSIDER I have FOUND A
PROBLEMATIC area ...
GUESS WHAT... Your switch is
WIDELY AVAILABLE in large numbers (quite popular (a huge clue)..
Check them out:
ROCKAUTO (examples)
1998 JEEP GRAND CHEROKEE 5 9L V8 Headlamp Switch RockAuto
Product detail:
More Information for OMIX ADA 1723429
Notwithstanding that
screaming clue...
Each door and the TAIL-GATE also have
contacts
which can jointly or singularly contribute to the problem.
Putting some body sealant (or play-dough) on the tip of each plunger... ( I would simply
remove THEM and TAPE OFF the
connectors to
TROUBLE-SHOOT)...
Again: hugely popular parts
1998 JEEP GRAND CHEROKEE 5 9L V8 Door Jamb Switch RockAuto
Rear tail-gate (switch)
More Information for STANDARD MOTOR PRODUCTS AW1048
Door contact (examples)
More Information for STANDARD MOTOR PRODUCTS DS875
Actually... including the courtesy timer module... this is a fairly complex circuit to trouble-shoot...
I hope I am helping.
I like electronics, circuitry (etc.)... Please feel free to comment
me or EVERY "FIXER" for more depth... &
HAPPY HUNTING.
Carnac the Magnificent