Basic electrical help needed

[Nerdy Norm]

I'm having trouble getting sound from my horn. It's a 12V DC horn, and I've already made the following tests:

Horn connected directly to battery terminals - works fine
Horn connected to wiring loom - just a click sound
Tested continuity from power and earth between rear battery and front loom - OK
Tested voltage coming from front loom - 12 volts
Tested voltage at horn with button pressed - drops to 8 volts
Bypassed switch by earthing horn direct to frame - still just a click sound

Thinking logically, this tells me that:
1. The horn works
2. The switch isn't the problem
3. The wiring is OK (as far as continuity and voltage are concerned)

So the bottom line is that the horn works fine when connected directly to the battery, but just clicks when connected to the other end of the cables (even though continuity and voltage seem to be OK).

That's about the limit of my electrical knowledge, so I'm guessing that I need to test current and/or resistance - where do I start?

Thanks!

[coaster]

You have done well so far using the process of elimination. The next step would be to run a wire direct from the battery to the horn, if that works then you will know there is a problem with the loom (possible high resistance in a crimp/terminal?)

Good luck

[Nerdy Norm]

Thanks!

Whilst I came indoors to defrost, I put the test battery on charge for half an hour. Guess what? Now it seems to work fine. I can only think that the battery was just a little bit low on charge after all the messing about testing I've been doing. Whilst it worked when the horn was connected directly to it, a couple of metres of loom and the odd connector or two must have tipped it over the edge.

[coaster]

Glad you got it sorted Norm