100 Series cruiser electrics issue

[BEU77y]

Firstly, I can answer part of my own question, in that this only happens when we have rain. So I know something is getting wet and making the circuitry crazy.

We don't even have to get alot of rain, just a mm or two will do it. First off, the air horns go off of their own accord and don't stop until the compressor gives in - usually accompanied by some smoke and a foul burning smell. I remove the horn fuse and all is fine on that front then (other than I don't have a horn until the fuse goes back in).

It also messes with the central locking. You turn the key in the lock, which unlocks all the doors, but as soon as you open 1 door, it locks itself back up and you have to unlock it all over again to get any other doors open. Once you get in and shut the door, it then locks and unlocks of it's own accord. The trip computer is also a scramble - it shows everything, Trip A, Odo B and the odometer reads 88888.8km (it's done 260k+, not 88k). Then there's the fuel gauge. If I switch to my sub tank, the sub light comes on but the gauge doesn't move. If I open the driver's door whilst it's doing this, the trip computer rectifies itself to what it should show and the fuel gauge shows the correct reading. Shut the door and drive off, and the trip computer goes crazy again.

When I get out of the truck at my destination, I leave the doors unlocked. When I get back to the truck and try to get back in, it's locked itself up in the time I've been away from it.

When it stops raining and dries back out, everything functions normally again.

Any ideas what is shorting out and causing the problem, or where to start looking?

[JWB]

As a un-educated guess I'd go over the electrics in the drivers door

[DAZZ]

Sounds like a bad body earth. Check the main earths from the battery to the body and chassis. and between the body and the chassis. If one of these earths is loose or corroded it may only be a problem when wet. Maybe unbolt them clean and protect them then refit. There is a lot of earth small earth points in late model vehicles so could be one of these as well.