Vehicle Horn Doesn't - Frustrated!!

[AdamB]

Hello all Funsters, I have a 1999 MB Vario 814D Campervan conversion (24V system). The horn doesn't work and I have been so confused trying to work out why. I am using a multimeter and would expect to find 24V at the horn terminals but I am reading about 7mV that goes up to about 450mV when I press the horn. I have checked the fuses and the relay (that clicks) and even that only reads 7-450mV. What could be wrong? Any assistance or advice would be welcome.

 

[donkey]

Horns tend to be wired with a positive feed and the negative is earthed via the horn push. If yours is that type then you should have 12v at the horn. I would start by checking and double checking the horn circuit fuse.

Geoff

 

[mitzimad]

two types of horns one wire and two wire two wire ones eatrh at the switch single wires you get power to the horn from the switch and they earth via the fixing with either you should get 24v at one terminal with the switch closed /button pushed if your not getting power check fuses and then check for power at the switch

 

[mitzimad]

you can test if the horn works across a battery

 

[pappajohn]

I have checked the fuses and the relay (that clicks) and even that only reads 7-450mV

The relay may be clicking but that doesn't mean the contacts are making contact.
Change the relay as a first step......unless you mean it's 7 to 450mv at the trigger wire at the relay but then that isn't enough to trigger the relay anyway.

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[dabhand]

If it works with a direct feed from the battery it could well be a connector terminal issue, I had the same problem on a previous m/h, put new spade terminals on and it worked

 

[Popty]

If you're getting Mv at the horn, then it's probably bad connections or corrosion in the wiring, or a combination of both, corrosion plays havoc with wiring and voltage, easy way to describe it is, treat it like a garden hose, no problem (when there is no restriction)then water flows easy, put your foot on the hose and water flow slows or stops, that's what corrosion does to electrics, look for any green verdigris on connections and cables, the corrosion stops electricity flowing properly

 

[pappajohn]

Pull, or short circuit, terminals 87 and 30 on the relay plug and connect together.
If it works it's definitely the relay