How can i put the washing flude in montero 2003 ?

check horn relay works
get a 12v probe and test the horn switch works when pressed
12v should be supplied to the horn relay coil contact when the horn switch is pushed on.
Also check the fuse.
Check voltage going to horn when pressed
horn might be negatively switched so 12v positive is on one side of horn and relay switches ground negative .
You will find the horn relay under the bonnet in a relay compartment most likely

Do you have an antitheft system? If disarm it. If not you may have an electrical issue

PLEASE DO NOT TRY ANY THING OUT OF YOUR OWN SINCE IF YOU FIX WITH A HIGH FUSE CAPACITY IT WILL NOT BLOW IN SHORT CIRCUIT AND YOUR CAR WILL TURN INTO FIRE IN SECONDS.
SUGGEST YOU CHECK WITH THE MANUFACTURER OR CHECK INTERNET FOR FUSE BOX FOR CORRECT FUSE.

First you should check the fluid levels of your transmission fluid. The fluid can be low and need a little added to it, but check the level first.

sorry to put it this way but WHO CARES.just change the belt every 60k.regardless of what the makers say....(they get you to pay for the bits when they break dont they.)

is it true that I have to put my montero in reverse to engage 4 wheel drive first?

Yes it is the condensor.

Have it checked and replaced.

check the fuse box on the driver side of the car underneath the dash near the door the fuse is probably blown

I looked this up and got that a 2004 endeavor has a 3.8l and the 2003 montero has the 3.5l engine. the oil filters have different part numbers for each engine.

ok this needs to go in to a mechanic now this will not cost more than $100 around $40 maby to get it fix depending on what is leaking