03 f-250 horn wiring

i am trying to wire a relay into my horn circuit in my 2003 ford f-250 superduty w/ 6.0L diesel. i found the blue wire up to the column but when i wire it into series w/ the relay it is not enough to pull in the relay. also this wire is 12v+ dc when the horn is not sounding then goes to 0 when sounding. i think i need a different wire like the one that goes to the horn

What are you trying to do with this wire? The negative output provided by this switch should be plenty strong enough to activate a relay.

i am trying to power up a relay to activate an air horn. when i wired in the relay into series with the blue wire going up to the colmun to the horn switch the horn doesn't work it won't go through the coil on the relay. The wire is constant +12vdc so i can't put the other side to ground. I need to find the relay that this blue wire pulls in or the wires going to the horn itself as the horn itself is not accessable.

The tech sheet from dei lists it as a negative trigger. The relay should work just fine if you wire it like this 85 Fused +12V Constant supply 30 Fused +12V Constant supply 87 +12V Output to device 86 Factory horn wire (this shows ground when the horn button is being pressed) 85 and 86 are interchangable they are just energizing the coil. Is this how you wired it and it is not working?