Ford F250 upfitter switch question

Hello all…newbie to the forum here. I have a question about installing a shocker series set. I will be using my stock toggle switched in my 2006 F250. The one will be to power the compressor on and off. The second switch will be to toggle from factory horn to train horn. When i switch it on to train horn, will this disengage my factory horn, or will the factory still come on along with the train horns?

I would rather have it set up to where either one of them will blow, but not both at the same time. From what Ive seen to set up, the toggle would just tap into the factory horn wire, which makes me think that they would both blow at the same time.

Hopefully, somebody can shed some light on this for me.

Thanks, Patrick

Welcome. I know upfitter switches provide 12V but I don’t know if the relays for the small compressors and/or horn valves need 12V or Ground.

The control for an Oasis compressor is based on Ground so the upfitter switch would need to activate a small relay connected to Ground.

You can do what you want with a Single Pole Dual Throw (SPDT) Relay. They have five pins and basically can divert a line to either one of two gates. The relay would be triggered by a toggle switch which in your terms would mean (Train Horns, or Stock Horns). I’ve attached a simple circuit drawing to show you how you’d need to wire it. Any questions, let me know.

Thank you all very much. That info is what I needed. Great Forum here!!!

Did you every get the horns to work? I have looked at the diagram and am stuck. The stock horn uses the horn pad a the ground to make the horns work. So did you connect the relay to the blue wire under the dash or the power wire to the horns? If you connected to the power wire do your air horns sound when you flip the switch? I have read so many articles on different ways to do this, but I am just getting more confused the more I read. My plan was to cut the blue wire and attach that to post 30 and 87a on the relay and then attach the air horn wire to 87 and the upfitter to the remaining two post on the relay for power and ground. but if there is no power on the blue wire the air horn should not work. Please help I to have a 06 F250 and am looking to finish my installation. Thanks

You need to just work through it step by step so it makes sense. Plus you need to know which wires in your car do what. When you’re doing this type of work it’s very handy to have a multimeter.

OK… so let’s say we go on the following assumption:

  1. Your horn has one ground wire (which you’ve seemed to have found).
  2. The other wire coming out of the horn will be a power wire which is energized when you hit the steering wheel button.

Your air-solenoid for your air horns works exactly the same way (one wire is ground, the other needs power; do that and the solenoid opens - honk!). Which way round you get those two wires doesn’t matter; that’s why they are often colored the same.

So for a start, you could just wire the solenoid directly into the stock horn wires and you’re good to go. The obvious side effect of doing so is that both horns will go at once.

The SPDT relay described in my diagram above, acts like a gate to allow you to switch between one horn or the other. Let’s assume your relay is numbered as follows:

Focus on pins 30,87 & 87a - These are the switch part of the relay.
So basically to splice this relay into your existing circuit:

  • cut your positive horn wire
  • connect one end to pin 30, and the other end to pin 87a

Now test your horn … should still work as normal, since all you’ve done is spliced a closed relay into that wire. If you bought a NO (normally open) type relay, you will need to switch the wire from 87a to 87.

Once you’ve tested your horn still works, continue

  • Wire your air solenoid to ground on one wire
  • Take the other wire from the solenoid and connect it to pin 87 (or 87a; depending on your relay type)

Now you’ve got a setup where all you need is to activate the switch in the relay - which is done via the other two pins on the relay (85 & 86). These energize a small coil which flips the internal switch. So…

  • Connect one pin (e.g. 86) to ground
  • Now test your upfitter switch wire (possibly the blue one) to see whether it supplies 12V when you enable the switch inside the cab. If it does, then simply connect that to the other pin on the relay (i.e. 85)

If your blue wire doesn’t carry 12V with the upfitter switch engaged, then you have to find another option - remember all you need on pin 85 is 12V+ and the relays switches over from stock horn to air horn.

Anyway… I hope that’s helped.

That is what I had figured out, my concern is more specific to the ford horn wiring.

  • The upfitter switch powers the relay
  • The blue wire is the ground for the horn via the horn pad
  • There is a 12v wire to the horns yellow/green that is a constant 12v with key off

So if I use the 12v wire to pin 87a and 30 I think when I switch the upfitter on that will cause the air horn to sound. Not the horn pad.

If I use the blue wire then I have find a 12v source for the solenoid

My next thought would be to ground the solenoid to the neg side of the factory horn (don’t even bother with the blue wire) and use the 12v yellow/green at the relay. Does this sound like it should work?

Thanks for all your help.

I think I would have to ground the air horn solenoid to the factory horn wire and not just to a ground. If it was just grounded to the frame I think it would cause it to sound when I flip the switch since the 12v wire has constant power supplied to the horns.

Also to help clarify, the blue wire when grounded honks the factory horn.

Not quite; If you have the upfitter wired to pins 85 & 86, and 12V (yellow/green) constant going to pin 30, then all it will do is switch power to flow out of pin 87 instead of 87a.

What you have on the Ford is a negative switched system (via the horn pad). So wire both the solenoid earth and the horn earth wires into the blue wire.

So basically - the solenoid and the main horn get grounded by the blue wire and therefore the horn button. What the relay does is to determine which horn gets the power.

[Edit> here’s an old drawing I found which may help visualize the negative switched thing…

Thanks, I think I may have a plan and will post my results.

The plan:
85 Upfitter 12v
86 Ground
87 Air Horn 12v
87a Yellow/Green 12v
30 Yellow/Green 12v
Ground Air horn solenoid to factory horn ground wire

All my questions were answered too!