Want to wire air horn compresser to the steering wheel horn wire.

Problem: Compresser draws 18 amps and stock horn wire is fused to 15 amps. Need a relay set up somehow/where.

Will wire the horn wire to a single pole, dual throw switch so I can use either setup when I want. But don't know how to place the relay? After the switch and before the compresser? Or what type I need?

Get these where? Radio Shack I am guessing?

Let me know your thoughts please . . .

 

I am not sure what horn system you have on your truck now. Are you sure you do not have a horn relay already? And if you do, the horn button in the steering wheel will ground the wire, not switch the +.

Are you working on the 06?

 

Yes, '06 F 250 PSD. So the horn wire is a ground wire then. So wire the + to the bat w/ a 20 amp fuse? Then run the ground to the switch setup? I was only going by the fuse box setup @ 15 amps.


Thanks for the direction. Let me know what your approach would be.

 

I was looking at the diagram for a 2005 f150. My first approach would have been to tell you to find the darkblue wire running up the column to the horn switch, cut it, and put your switch in there.

But, looking at the diagram, there is more stuff on that wire which includes the security module(I am guessing this blows the horn when someone tries to steal the truck?).

So the simplier more foolproof way, would be to put the switch inline with the wire going to the horns themselves.

Like I said I am looking at a 2005 f150 diagram. It shows the horn relay in the fuse box under the dash. The main wire leaving the relay is a yellow with a lightgreen stripe.

I would get a single pole, double throw switch rated at least 15 amps. Cut the yellow/lightgreen wire leaving the factory relay, and hook the wire coming from the relay to the common of the switch. Hook one of the other terminals of the switch to the other end of the yellow/green you just cut.

The remaining terminal of the switch, I would hook to a small wire and run out under the hood and hook it to your new 30 amp Bosch style relay(foglamp relay) coil. Ground the other side of the coil.

Then do what you said, and run a 25 to 30 amp fuse off the battery to feed the relay and then the air compressor

 

I can't find a relay on the dash fuse box, just a 15 amp fuse for the horns. I will look for the horn wire from the horns to see what color they are but I really don't even know where they put the stock horns.

Doing it this way will make the alarm sound which ever horn the switch is on, correct? Mentioned by another was cutting the dark blue wire and putting it on the switch commen BUT the the factory horns always blow with the alram vs. the air. So wouldn't you think the dark blue would work? It is a ground I am assuming given your earlier comment.

Where do you get a Bosch relay coil? Auto parts store? Radio Shack?
Thanks for your patience and insight.

 

You can go ahead and try the darkblue wire. The common of the switch would go to the wire going to the steering wheel, and one of the other terminals would hook to the other end of the blue you just cut, and the other terminal would hook to a small wire going out to the Bosch type relay. In this case you would have to take the bat + hot wire and hook it directly to one side of the Bosch coil, and hook the other side of the coil to your wire that runs to the new switch. This would activate the Bosch coil when the steering wheel switch grounded the wire.

You can get these relays anywhere. I even saw Walmart has a foglamp wiring kit that has the relay and the wiring in it for foglamps. They may even have just the relay hanging there somewhere.

 

I'll try it out and Thks!