On my 1998 Dodge caravan nothing works such as horn, headlights, breaklights, door locks, etc. without the key being turned to accessories or ignition. When I turn on the key these everything works. I have checked fuses, relays, etc. but can't find the problem. I have studied schematics in a manual from the parts store but haven't found a circuit that could cause the problem.

Please don't type in all CAPS, it is considered SHOUTING and is difficult to read, plus you have absolutely no Punctuation! That is not one sentence. No idea when one part end and another starts.

The issue is the horn switch itself or the 'clock spring' in the steering wheel.

Test and trace the switch and wiring.

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Security engaged, Lock and unlock doors with key until horn stops.

door locks cycle as you are driving? if this is the case a common cause is the switch going bad that shows the sliding door is closed.

sounds like you have a security problem, (antitheft) , when it acts up take the key and put it in the outside door lock switch with the door shut and window down and lock and unlock the drivers door with the key,it should quit, if not try locking and unlocking car with key fob(remote lock,unlock switch on key chain), if that dont work , you have further prob. with security system and take it to a shop. if it quits with the key process and then comes back on , the sensitivity might be to high. does the horn go off with the lights?

on the positive side battery cable their is a small wire coming off cable end, is a fuse connector an the fuse is bad .

the alarm is active and the door lock dosnt switch it off

think it's supose to do that if I read this right

check the fuse migh of gone out

Battery Constant 12v+ Positive Wire (+): Black/Orange And Red/White
Battery Constant 12v+ Positive Wire Location: Ignition Switch Harness
Starter Positive Wire (+): Yellow
Starter Positive Wire Location: Ignition Switch Harness
Ignition Positive Wire (+): Blue (16 Gauge)
Ignition Positive Wire Location: Ignition Switch Harness
Second Ignition Positive Wire (+): Yellow/Red
Second Ignition Positive Wire Location: Ignition Switch Harness
Accessory Positive Wire (+): Blue (10 Gauge)
Accessory Positive Wire Location: Ignition Switch Harness
Second Accessory Positive Wire (+): Orange
Second Accessory Positive Wire Location: Ignition Switch Harness
Parking Light Positive Wire (+): Black/Yellow
Parking Light Positive Wire Location: At Headlight Switch
Power Door Lock Positive Wire (+): Orange/Violet
Power Door Lock Positive Wire Location: In Drivers Kick Panel, White 6-Pin
Power Door Unlock Positive Wire (+): Pink/Violet
Power Door Unlock Positive Wire Location: In Drivers Kick Panel, White 12-Pin
Door Trigger Negative Wire (-): Yellow
Door Trigger Negative Wire Location: At Headlight Switch
Domelight Supervision Wire: Use Door Trigger (Requires Relay)
Domelight Supervision Wire Location: N/A
Horn Negative Wire (-): Black/Red
Horn Negative Wire Location: At Steering Column Harness
Tachometer Wire Negative Wire (-): Gray
Tachometer Wire Negative Wire Location: At PCM, Connector 1, Pin A7. The PCM (powertrain control module) is located on the firewall next to the wiper motor.
Brake Light Positive Wire (+): White/Tan
Brake Light Positive Wire Location: At Switch Above Brake Pedal
Factory Alarm Disarm Wire (-): Black/Orange (To disarm requires a (-) negative through a 1565 ohm resistor and an extra relay to connect.)
Factory Alarm Disarm Wire Location: In Drivers Kick Panel, White 12 Pin Plug
Factory Anti-Theft System: N/A
Factory Anti-Theft System Location: N/A

No preferences as to charger, as long as it has trickle charge option (slower, but better for battery). Would like to see battery load test done by parts store to see battery condition, but a simple charge may be it. Let me know how it goes, hopefully you will have it up and running soon.