Horn Amperage/Relay Question(s)

[LieutenantCracker]

Hi!
I recently came into possession of a set of horns from a 1977 Cadillac DeVille, and am interested in replacing the OEM horns on my 1999 Mercury Grand Marquis, w/ them.
A simple-enough project, it would seem, but after I noticed that the Mercury's electrical connector that went from the car to the horns was different from other ones I'd seen, I compared the wiring layouts of both sets of horns-- and discovered that they were wired differently from each other:

*The Mercury horns have one connector, which has two leads (presumably positive & negative) and plugs into one of the two horns..... Then, a set of two wires splits out of the first connector on the 1st horn, and runs to a connector on the 2nd horn.
Just for the hell-of-it, I unbolted the horns from the car (still plugged-in) & set 'em on a piece of plastic, to see if they'd still blow without the frame's "ground"-- They did.;

*The Cadi' horns start w/ a SINGLE-lead connector (the kind I've ALWAYS seen on American car horns) (positive[?]), which plugs into the 1st horn. A seperate lead runs from that conn., to an other one, on the 2nd horn; which has a lead that runs out of it, to a conn. on the 3rd horn.
Presumably, "ground" is provided through the car's frame, to-which the assembly mounts.

Also, you undoubtedly caught the fact that the Cadi' horns are a set of THREE, but the Merc'y OEM-set is of TWO-- Will THAT be an issue w/ the Merc's fuse(s), relay, or otherwise?(!)

Thanks, in advance!
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RHODE ISLAND MEDICAL MARIJUANA

[MagicRat]

A typical electric horn does not have much amperage draw. I have used 3 horns in place of the original 2 on a number of American cars without difficulty.
The horn circuits I have come across all seem to be protected by a 10 amp fuse, which is above the power draw of 3 horns, so imo you likely could use 3 horns without difficulty.

As for wiring, I would suggest just use the positive lead from the stock wiring harness and make your own jumper wire to connect the 3 horn terminals. Try using the chassis ground as well, you may not need to use the ground wire at all.

[LieutenantCracker]

OK, Great!-- I'll test 'er out this evening, as soon as I get home.

Just to clarify, you're suggesting that I use both the OEM horn switch (in the steering wheel) & the OEM positive-lead..... NOT running a NEW positive-lead, and/or wiring-in a new switch, right?
When I first thought of getting some louder horns, I looked at the ones they carried at my local Advance "I Don't Know Nothing About Any of These" Auto Parts, Auto "Non English-Speaking" Zone, & O'Riley "Everything's On Backorder" stores. Some of them only provided vague instructions, w/ the single option of creating a whole-new circuit for the replacement horn(s)-- Including a "Remote" horn-button, mounted in the cab..... independent from the wheel(!)
Fortunately, I realized that I'd completely forgotten about checking Ye Olde Yard-o'-Junk (from-where my Ca'De-Ville horns untimately came!)

PLEASE don't misunderstand: I'm NOT questioning your advice-- Just making sure that I'VE got it straight!


Thanks a lot!
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NO2 VAPORIZER

[shorod]

The horn button in the steering wheel just triggers a relay, so all the significant current switching is done by the relay. There will just be a few milliamps flowing through the horn switch, and that current won't change due to going to a different horn setup.

-Rod

[MagicRat]

Originally Posted by LieutenantCracker

Just to clarify, you're suggesting that I use both the OEM horn switch (in the steering wheel) & the OEM positive-lead..... NOT running a NEW positive-lead, and/or wiring-in a new switch, right?

That is correct!!

As shorod noted, it's the fuse and relay that take the electrical load of running the horns. So, in the extremely unlikely event that the circuit is overloaded, your fuse will blow before any wiring damage occurs.