1994 E350 box truck 7.3 2wd auto
I've got 12.5v at new batt but 10v at horn switch.
if i hot wire horn from batt it sounds but jumping horn switch leads got nothing
I confirmed horn switch works by reading continuity when pressing horn "pad"?
just replaced 15a horn fuse which was blown
fuse was actually physically blown apart - the plastic case was in two pieces
I get 12.5 on ea side of fuse
so somewhere between the fuse and the steering wheel connector I lose 2.5v
leads me to think a partial ground in harness might be bleeding off some volts???
don't know why or if that could have previously blow fuse ?????
edit: just checked with key on, horn switch legs inside steering wheel shorted (jumpered) ie simulate horn being pressed - I get no voltage at hot wire going into horn
i thought maybe I'd get the 10v I see at the steering wheel but that wasn't enough to fire the horn...but i'm getting 0

I can't imagine the nightmare of trying to find a fault in the harness...can I just run a wire up to the dash and put in a push button switch?
it obviously wouldn't be going thru the fuse anymore, does that matter?
or does someone have an easy way to fix the "right" way?
Thanks for any tips

okay this is weird LOL I was testing as above and had the switch legs jumpered and came in to post this question and 15mins later the horn starts blasting out in the driveway!!!
it now works as intended...I should go buy a lottery ticket :-)
so nothing to do with volts and ohms just a gremlin issue???!!!

 

Check my signature below.

 

ok, thanks

 

Check the Y/LG (yellow/light green) wire, do you get ground signal when you press the horn button there? Basically you find a good ground, perhaps from steering column rod or your knee panel, just measure continuity of that with Y/LG wire.
There are several sections you have to test:
1) From G200 to Y/LG wire (the relay trigger wire)
2) At the horn relay C181 check circuit 460 for present of voltage on Y/LB (yellow/light blue), 2 of them, not the DB (dark blue) wire. You remove the relay first then measure voltage (always hot as shown above).
If you know how to bench test the relay you can do so as well.
3) I run out of time gotta go, please test those first.