Horn(s) won't blow

[gazelle]

'04, 155K miles, aftermarket (Fiamm I think) horns professinally installed right after purchase by original owner. I bought 2+ yrs ago with 53K. I hear a "click" when pressing the switch.Neither horn works. (Only one horm may have been working sinse I've owned it. I do not know. It "sounds" (no pun intended) like a horn problem rather than a switch or relay to me. I've not looked but some have an "adjustment screw" I am told.Any suggestions as where to look first ? What (if anything) will need to be removed to replace them ? Thanks for any help !

 

[bluesdog]

Try the simple stuff first.

The wires connected to the horns may be a bit corroded at the connecting tabs on the horns. I'd pull 'em off, clean with electrical contact spray and put them back on.

If that fails, check that the wires are actually delivering current.

Fiamm horns were likely installed with a relay, and relays do go bad, so if no power is being delivered to the horns, your next challenge would be to locate said relay, and replace it with a good one

Good luck

 

[SouthernCruizer]

when i had air horns, i constantly had problem with relays. I'd check there first.

 

[BkerChuck]

The audible "click" leads me to think relay above anything else.

 

[ionbeam]

The audible CLICK leads me to think the relay is good.

In a perfect world you would put a volt meter across the terminals of the horn and press the horn button. If you read 12 volts and the horn doesn't sound the horn is bad. No 12 volts at the horn, then put the meter across the coil of the relay and push the horn button. If you don't see 12 volts then you have a wire, switch or fuse problem going to the relay coil. If you read 12 volts across the relay coil then the relay is bad or the wiring between the relay and horn is bad.

 

[Fred W]

Most aftermarket horn relay harnesses will add a fuse on the 12V power cable running from the battery to the relay. Check that.

The relay's coil is usually driven off the OEM horn signal wires.

 

[Geezer]

The relay is likely energized by the original horn circuit, but the power that the relay switches and sends to the horn should be a separate source that is fused and connects directly to the battery or some other power distribution that was added. It is pretty simple if you look at it one piece at a time.

1) Voltage at the horn connectors when the button is depressed? - If yes then the horn itself is likely the problem

2) Voltage at the relay output but not at the horn? - Wiring, connector, between the relay and the horn or ground issue at the horn

3) Voltage at the relay line input? If yes, but no voltage on the relay output then the contacts in the relay are suspect.

4) No voltage at relay line input? There may be a bad in-line fuse or wiring issue at the source of the power. The relay is likely energized by the original horn circuit, but the power that the relay switches and sends to the horn should be a separate source that is fused and connects directly to the battery or some other power distribution that was added.

 

[rbentnail]

...clean with electrical contact spray...

Be careful if you decide to do this. Most contact cleaners available commercially will melt plastic.

 

[gazelle]

Thanks for the responses everyone ! (Just realized that I shoulda posted this under the "problems" banner.) Regardless I pulled the left horn in order to get to the connections, duct taped down the horn button (only two hands and my tester only has probes), attempted to check the voltage and for zero...and then the horns both came on and scared the $&(! outta me ! Removed the duct tape and they work fine. I'm assuming a bad connection and I moved it just enought to make contact. Also assuming that they are wired in series and if one connector is bad neither horn will work ??? 400 mile ride tomorrow into the mtns of W NC and E TN...no time to properly clean them tonite ! Thanks again !

 

[bluesdog]

WD - 40 and similar so-called cleaner/lubricants will eat ABS, but a decent electrical contact cleaner is mainly just isopropanol with a bit of butane. I recently used some on the contact pins for a tube-driven guitar amp to ensure adequate electrical contact.

With a little care, it should not harm anything unless it is seriously oversprayed. Also, it tends to evaporate rapidly. Don't use any contact cleaner designed for cleaning/lubricating potentiometers, such as volume controls on A/V equipment, as the lubricant may indeed damage paint or plastic.

Once you have cleaned the connections, I recommend an application of ACF-50 Awesome stuff, which works as advertised.

 

[Fred W]

...and then the horns both came on and scared the $&(! outta me ! Removed the duct tape and they work fine. I'm assuming a bad connection and I moved it just enought to make contact. Also assuming that they are wired in series and if one connector is bad neither horn will work ??? 400 mile ride tomorrow into the mtns of W NC and E TN...no time to properly clean them tonite ! Thanks again !

Huh? Who the heck would wire their horns in series. That's a really bad idea. You will want to fix that and rewire them.

For one thing it means that your horns will not be nearly as loud as they could be if they were wired in parallel. Being in series reduces the current through the horns, which reduces the power by the square of that (P = I2 * R) Since you have a dedicated horn relay the total current draw should not be an issue for the wiring harness. Second reason is the one you just discovered: Being in series negates the redundant safety factor of having two horns.

PS - Glad you found your problem(s)

 

[Geezer]

They are not likely wired in series. It may appear that way if you have two wires on one connector at one horn, and one of those wires goes to the other horn. That may look like a series circuit, but it is parallel.

Since you now have functioning horns, you may be tempted to leave it and call it good. Don't do that because they will fail again at a time when you need them to work.

If both horns worked after you wiggled one connector then you have a good clue where the problem is. It would be at that connector or before it back to the relay.