Polarity for Horn wires

[goinsvt]

Hoping someone can help me with wiring some air horns that I've installed. I'm going to splice a relay into the OEM horn wires so that I can press the steering wheel horn button to activate OEM horn when upfitter switch is off and activate air horns when upfitter switch is on. I don't have access to a volt meter right now and need to know the polarity of the wires going into the horn wire harness. Is the red wire (+) and the black wire ground as logic would dictate? I only want to splice into the (+) wire so I don't want to make any bad assumptions. Thanks.

 

[goinsvt]

Just as a sanity check - I'm wiring the relays as described below to allow the factory horn to be active when upfitter switch is off and air horn to be active when upfitter switch is on. Please let me know if something doesn't look correct.

Pin 30 - (+) wire from OEM horn button
Pin 80 = (+) wire from upfitter switch
Pin 85 = ground
Pin 87 = (+) wire to air horn solenoid
Pin 87a = (+) wire to factory horn

 

[The Car Stereo Company]

i am guessing you mean 86 instead of 80. but you do have a coulple wires backwards. 87 and 87a are normally closed so when the relay is not active these two are a pass through. so when you press the horn current will pass through 87a. once you flip the switch, then 87 and 30 become common.

so you should have it like this

85 power (or ground)
86 power (or ground whatever is opposite of 85)
87 horn input
87a horn output
30 to train horn relay

 

[goinsvt]

Thanks Busa. Was hoping you could chime in. If its warm enough, I'll try this tomorrow.

 

[The Car Stereo Company]

im not on the forum much...... but i saw your post......

 

[Yukon Joe]

Noah is very helpful when it comes to those pesky relays!

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[jocdmd]

I think the yellow wire going to factory horn is the "+". But follow whatever Noah says.

 

[goinsvt]

Thanks @jocdmd. I measured with the volt meter this morning and you're right, red/yellow is the positive lead going to the factory horn.

 

[Greybeard]

So if the polarity is crossed will the horn suck instead of blow?


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