Compression Ignition Addict
Join Date: Feb 2008
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i may have to think about this a little - i haven't messed with the horn circuit on this truck, so bear with me a little bit...
IME, most of the time the horn circuit has one wire to the horn, which is then grounded to teh chassis through it's bracket, in which case the wiring above should work.
The reason we have this relay between the truck and the stock horn is to stop the stock horn from honking when you have the upfitter switch "on." a SPST relay on the horn wire, firing this or another SPST relay, when you had the switch "on" you would get BOTH horns.
assuming what you say is true, and without additional information, i see two possiliities, you'll have to help me determine which is correct:
1) the horn circuit is ground side switched, like so:
+12 -> horn -> switch (horn button) -> ground
in which case you would modify the wiring as such:
30 : truck side of stock horn wire
85 : upfitter switch
86 : ground
87 : pin 86 on train horn relay
87a : horn side of stock horn wire
the train horn relay would be as such:
30 : fused +12V
85 : fused +12V
86 : pin 87 on SPDT relay
87 : Load (Train horn compressor/control box/whatever
2) the stock horn is hot side switched, has two wires and you are on the ground side - it would be WAY easier to wire on the hot side of the relay.
someone please double check my logic, as i'm trying to picture this in my mind.. i should probably draw it out, or go find some relays and wire it up...
I've actually thought of a way to simplify the first schematic, in the case of #2 here...
Last edited by Safir; 03-25-2008 at 04:47 PM.