faulty horn... replacement?

[Zimbok]

Hi, my van is coming up for its MOT and I need to get the horn fixed. It hasn't worked for a while and I thought it would just be the fuse.

Anyway replaced fuse, wasn't that. Searched forum and took steering cowling off to check connections etc, not that. Finally there was a mouse like squeak from underneath the van and checked. (the sound may well have been there before but was so quiet it was hardly noticeable). Didn't know the actual horn was there, just by the spare wheel carrier. Tried WD40'ing it, prodding and the like. Now seems totally buggered with not even the previous squeak.

Went up the scrapyard and got one from another vehicle (not sure what car it came from), but it doesn't have the two male spade connections that are on the van horn, only the one. The guy said to try earthing one of the two female spade connector wires on the van and connect the other one to the male spade connection on the replacement horn.

First attempt the fuse went bang (no 16). Replaced the fuse and tried switching the wires around. With the two van female spade connectors, one goes to the new horn male spade prong and the other is earthed (length of wire one side has a male spade connector which I connected to van female spade connection, and the other side of the wire is bolted to the bodywork).

The new horn works now BUT it won't go off . If you switch ignition on the horn sounds non stop (like a car alarm). I have now disconnected and put the old non working one back on.

Am I wiring the new one incorrectly or am I simply barking up the wrong tree and should just try and source a working like for like replacement.

[andyb]

Hi
Ive no idea on later models but the horn should be a simple circuit if it hasnt been modded.

There should be a live feed to the horn from the fuse box possibly black yellow
then a earth from horn brown which runs to the switch in the steering wheel.

Sounds to me like youve fed it a live from the fuse box then earthed it to the chassis - hence horn on all the time.

[ewenmaclean]

Hello,

I think you're being pretty resourceful finding another type of horn - it's a good thing to do recycling where possible in my opinion. The feed wire from the horn is live, and the horn switch earths it through the horn. The reason why the fuse went is probably because the body of the new horn is earthing the live wire directly. With it the other way round the horn is always going but this time I suspect the body is earthing the horn like a switch.

If I were you I'd take it off the body of the van - connect it up as it is now, and then bridge between the van body and where you have designated an earth connection. You may well find that you need to isolate the horn from the chassis using a rubber mount or something. If not then try and find a horn whose body is not connected to either pin like the vw one.

For the MOT you just need a functioning horn so you could put an inline button in what you have now.

Ewen

(E D I T - just saw andyb got in before me - seems we agree )

[82JEW75]

Or you can get a VW horn for under a tenner from the usual suspects.

Did you check the original horn? Remove it, connect a bit of wire to each terminal and touch the ends of these to a battery. It should just about blow your ears off! If the horn works then the problem is elsewhere.

[Oldiebut goodie]

Sometimes all the horn needs is a slight adjustment on the screw that moves the make and break contact. Look for a small screw that has a locknut on it, loosen the locknut and turn the screw, whilst connected to a power source, until you get the loudest sound. The horn on my boat is always needing adjustment like this.

[Zimbok]

Thanks all for your advice / comments, very much appreciated. As always I learn something new all the time.

I must admit I checked on Ebay this morning for a T25 like-for-like replacement and although I didn't see any I noticed that motorcycle horns were very similar i.e. with the 2 x male spades so I popped into a local bike dealer earlier and picked up a brand new shiny one for twelve pounds.

I have just fitted it and the horn works just fine. First time it's worked for a while

Now to book in for the MOT. I have posted another of my problems i.e. flashing temp light / needle issue but I hope that isn't an MOT failure. Fingers crossed!