It will work either way, since the horn is an intermittent-use item. Anything that draws constant current like a heater fan motor, radio, wipers, etc., needs to go to the downstream side of the ammeter so the true charge current to the battery can be monitored. The generator or alternator will supply all the constant loads first, such as ignition, lights, heat, etc., and whatever is left over goes to the battery to recharge it. If the load exceeds the capacity of the charging system, the battery makes up the difference, and you'll see the ammeter go to "discharge". Plug in the cigarette lighter if you've got one, and watch the ammeter take a dive momentarily until the generator can catch up!
Jerry
Last edited by Hotrod Lincoln; 02/23/2012 4:39 AM.
