Rough Idle... Fixed when horn fuse is removed

[jnorman15]

I have read a thread on this one before but noone has given the reason yet. When I am in gear with brakes applied, the rpms drop and the car runs rough... as soon as I remove the horn fuse, the rpms corrects and everything is ok. Any ideas why?

[JonsMazda]

Hmm, anything else hooked up to the fuse box?

[Dave_The_BMXER]

horn fuse is also tail light fuse.

[Default User]

How in the world did you decide to pull the horn fuse?

[jnorman15]

I've read a post before that said to do it because the brakes work off the horn circuit, so I pulled it and it worked. The tail lights don't work with the horn fuse pulled. That post did not offer any solutions though

[Kappa]

i wanna know how someone found this out... lol

[Dave_The_BMXER]

Curious what happens if you turn on all your accessories (fan/highbeams/window heater etc)

[Flagrum_3]

Don't know if this is the same but at work we had a New bus that everytime you pressed the horn the right wiper would wipe lol.It turned out to be a circuit issue, but they use a relay not a fuse...Who knows probably a short/break or corroded connector somewhere?

_3

[rukus]

lowered idle when in gear and with brakes on? isnt that normal?

[jnorman15]

Ya but it runs abnormally rough. To about 400 rpms and steady