I am trying to put a siren in my truck and would like to hook it up to the existing horn. The problem I am having is that I am not sure if my horn is greater or less than 2 amps. Here is the part of the instructions.....

The horn ring transfer circuit of the siren is
capable of switching a maximum of 2-amperes.
Some vehicles do not have a horn relay
and, consequently, will draw more than 2-
amperes when the vehicle horn is activated.
Consult your vehicle service manual or a
qualified mechanic to determine the current
required to activate the horn. If it is less
than 2-amperes, perform the procedure in
step 3. If it is greater than 2-amperes,
perform steps 4 through 10.

I own a 2008 FX4
Any help would be appreciated.
Thanks

 

Take a look at your owners manual, page 305.

Relay R305 ( non serviceable ) is for the horn.

The fuse that feeds to horn relay is a 20A fuse, page 303. Nothing else is on this fuse.

Considering that relay is soldered into the fuse panel, you might want to still install a relay for the siren, using the power to the horns to trigger the coil.