I have a 1995 Isuzu Trooper. The battery goes dead unless u unplug the battery cable every time you turn it off. A the same time this started happening the check trans light came on and it fells like maybe the transmission is slipping????

fixya doesnt carry or sell products ---purchase from a dealer --auto parts store unkyard-online search

which engine, ill toss coin, land on v6
check fuses first.
wont crank? that grrrrr grrrrr grrrrr sound
jumper cable start it yet, why not?
or put in a known good charged car battery?
or using any battery charger charge yours?
or buy a new battery, (if rich)

if it cranks and wont start?
check spark x6 (scan it yet?)
if sparks ok try test fuel!
if test fuel fails 100% see bad belt below.

EVER REPLACE THE CAM BELT?
if not and over 60k on the last one
the belt is doomed, living on borrowed time.
got the V6?

Answering for ENGINE will not Crank !
Or the starter motor is SILENT !
Is the IMMoblizer lamp in dash telling you why?
good questions, sure it can.!
all electrics on cars are fused, (cept starter main)
lets for get the engine, (for now)
by no lights? that mean head lights are both dead? (if yes we fix this first) {easy}
head lights work key off, so..... is panic fail, prime failure mode.
if you meant the cluster lamps only, why not say so?

if the HL are out, the battery is dead or its cables are rusted (4 ends)
or fuse blow out in main box.

if the cluster lamps are dead and for sure the CEL lamp? then the ECU has no power, and engine will never run with that dead. or IMMO lamp stuck on.
CEL = check engine light if , out,key on, the ECU has zero power.

the radio is dead , is one more prime failure.
head lights win that argument.. but i'd bet cab fuse box are dead due to PCD box under hood dead.

So, open hood, see the PDC (main fuse box)?
you check battery voltage with neg lead of meter to body metal.
it reads:
12.6 vdc or more rested is a charged battery,.
$10 meter at walfart works.
if not, bingo. bad battery cables or ground. (the cables have 4 ends,and all 4 ends can rust or even be loose)

so next check the voltage in the main box at all main fuses.
i'd bet one fuse has 12v on one side and 0v the other is a clearly blown fuse.(there)
if you need a schematic we have it.ask

the symptoms are lost main power.
the tests are easy.
with any cheap voltmeter every made.
got one?, or must we work blind?
Recap:
No cranks (is IMMO active?)
no head lamps, fuses blown for them or mains blown
CEL lamp dead in cluster key on , ECU fuses blown
or cluster fuse blown.

from your limited hints, id say them mains are blown.

FL1 is the main fuse.
got 12vdc on both sides if fuse? if not all is dead. the fuse blows, changing out the alternator not pulling battery neg lug(very common reason)

post symptoms, we can not guess all the nine ways from sunday
to mess up.

all dead, , one dead, one lies., some dont glow, speed makes noise, or jerks.
the park lamp dimmer is dead>?
do warning lamps work, key, CEL lamps glows?
if not battery is dead, or fuse blown.

the cluster has one fuse, and fues need testing.

fuse that look bad are
fuse that look good, can in fact be bad, (hair cracks)
we use a voltmeter on both sides of fuses. 12v, and 12v.
good,
and the can have 2 or 3 fuses boxes, no didnt look yours up
you can at alldata.com

Are the battery an cables good ? Check the starter electrical circuit , voltage drop testing ! Why pull the starter , until you have to ! Starter Voltage Drop test the circuit before you pull the starter !

Try jump start with a freinds car befor you by a battery

The starter is on the drivers side of the 3.2 engine you will have to remove the cross over exhaust pipe to get at it.

bad generator

Try and shoot a little fuel in the throat of the throttle body or air cleaner to make sure its not a fuel problem .. thanks Jerry

Could be one of two things.

1. Your starter motor is no good.
2. If you turn on your lights and try to start the car and they dim to almost black, then you need to check the battery connections.