Had problem with headlights coming on by themselves - found fault due to water in Fuse Box in engine compartment.

A fuse can blow but physically look intact. How did you verify the fuses were ok? It could be that the 40A fuse 8 in the engine compartment fuse box has blown.
This supplies multiple circuits which are themselves individually fused in the consumer box inside the car.
The smaller 15A fuse 15 in the consumer box would normally blow under these circumstances but f the horn does not work as well and there are other things you have not listed that do not work like brake lights or headlights, it is definitely the under bonnet fusebox where the problem lies.
Good luck.

sounds like a fuse or relay ,have you checked the fuse box drivers side lower dash for headlight fuse(s) also in engine bay there is another fuse box with relays ,list will be on the cover ,i'd start there as power is going to bulb on one circuit , other than that the switch may not be working fully

see this steps and fix it use the VOM or DVOM. God bless you
The Cause: Most likely no voltage to the headlights because of a bad headlight relay, fuse, module, headlight switch, dimmer switch or wiring fault.
To figure out what's causing your problem, start by inspecting the main fuse for the headlight circuit. See your Owners Manual for the location of this fuse. It is often located in the power center in the engine compartment, but may also be in the fuse panel under the dash.
If the fuse has blown, replace it with a new fuse (same amp rating) and try again. If the fuse blows immediately, there is a short in the headlight circuit that will have to be found and repaired before the headlights will work. If the fuse does not blow and the headlights work, problem solved (for now). There may be in intermittent short or overload that caused the fuse to fail.
If the fuse if okay, use a volt meter or 12-volt test light to check for power at the fuse. Most headlight circuits are on (powered) all the time, so there should be voltage to the power side of the fuse. No power at the fuse would indicate a wiring fault possibly in the fuse block or in the wiring between the fuse block and the battery. You'll need a wiring diagram to trace the wiring circuit and find the fault.
If the fuse is okay and there is power, the next check would be to find the headlight relay or control module. If the system uses a relay, pull it out and shake it. If anything inside rattles, replace the relay. Or buy another relay and plug that in to see if that restores power to the headlights.
On systems that use a module control module or daytime running lamps, about all you can do is eliminate other possibilities such as wiring faults, a bad relay or headlight switch first. If the module is getting power when the headlight switch is turned on, but the headlights fail to come on, the problem is likely a bad module. The module may be located in the front area of the engine compartment (common on Fords), under the dash or elsewhere in the front of the vehicle. You will probably need to refer to the vehicle service literature to find the module's location.
If the headlight relay or module do not receive voltage when the headlight switch is turned on, a bad switch is your problem. Switches get a lot of wear and tear, so it's not unusual for a switch to wear out after many years of service. Replacing a headlight switch can be difficult depending on whether is it located in the instrument panel or on the steering column.
If your headlights work on low beam, but you have no high beam, or they work on high beam but there is no low beam, the most likely cause is a bad dimmer switch. The dimmer switch is integrated into the steering column mounted headlight switch on most vehicles, so if the dimmer is not working, you will have to replace the entire switch.
DO NOT attempt to replace a steering column mounted headlight switch without first disconnecting the battery and waiting at least 20 minutes for the capacitors in the airbag circuit to discharge. The steering wheel will have to come off to replace the switch. Crossing up the wrong wires in the steering column could set off the air bag and cause personal injury.
If a headlight switch looks like it will be difficult to replace, don't try to do it yourself. Take your car to a dealer or repair shop and have them replace the switch for you.

The fuses that protect your headlamp circuits are Fuse Numbers [4] (Left High Beam), [5] (Right High Beam) [6] (Left Low Beam) and [7] (Right Low Beam).
Fuse 4 is a 10 Amp fuse
Fuse 5 is a 10 Amp fuse
Fuse 6 is a 20 Amp fuse
Fuse 7 is a 15 Amp fuse
All are located in the Power Distribution Center in the engine compartment.

The difference between a 1999 Chrysler Town & Country with DRL and WITHOUT DRL is that one has a DRL module and the other does not. The headlmps themselves are wired exactly the same.

To make yours work, you would have to add the DRL module and reprogram your Body Control Module (BCM) to accept the DRL module. Doing it any other way would probably result in the BCM setting fault codes and possibly even causing malfunctions in other non-headlamp-related circuits.

Just solved this problem on our 2004 Isuzu Ascender. It was a bad relay located in the fuse/relay box which can be found inside the engine compartment. The relay is number 46 (HDM) on the diagram located on the inside cover of the fuse/relay box lid.

There are actually two of the same relays side by side in the fuse/relay box. To be sure this is the problem you can remove the relay from slot 45 and put in 46, the headlights should come on and stay on. Of course you will need to replace the relay which can be purchased and most GM/Chevy. The part number is: 15016745. I paid $52 for mine.

Oh, and be sure you use solid state relays only. The afore mentioned part number is a solid state relay.

The Battery junction box is located in the left corner of engine compartment, let me know if this helps.

the headlight pop-up circuit is different from the lights themselves. Check the headlight fuses in the engine compartment fuse box. If the fuses are good then check the headlight relay. It is in the same fuse box just behind the headlight fuses. (The headlight relay is the second relay from the right side of the fuse box. the relay at the far right is the electronic fuel injection main relay.)

swap fuse 45 and 46, if that works go to your nearest auto parts store and buy a new fuse. One fuse is for a fan exghuast the other has to do with the low beam.

Just a question from experience: Have you tried the brights? I have seen both headlights burn out simultaneously several times.

Moving on, the headlights are probably fed through a relay in the engine compartment box. Should be an embossed diagram in the box lid for which one is which.

ddlucia: there is one fuse box located in the engine compartment.
it is a large black box. it will contain the headlight fuses.
The other fuse block is inside the passengers compartment.on the drivers side. some of the cars had the cruise control fuses in this panel others were in the engine compartment.