Horn Relay

[the_lone_wolf]

Originally Posted by Baph

I fully understand the subject, and was essentially trolling last night.

Convenient

[DarrenSV650S]

Bumpety bump bump

My horn was working fine for ages then suddenly stopped working. Everything is wired up correctly and the horn works when connected directly to the battery. Putting the volt meter across the outgoing of the relay shows the voltage is constantly jumping between 0 and ~4V

Can I assume the relay is fooked? What would have caused this? The pins were covered in tape so they couldn't of shorted against the frame. Only thing that I can think of is that water might have shorted out the pins on the horn, but they're not exactly very close to each other.

[yorkie_chris]

Sounds like the relays buggered, but check the horn button with a test light too.... just directly connect a headlight bulb where it plugs into relay and see if it lights...

[DarrenSV650S]

There's definitely juice at the horn connectors because when the new horn stopped working I just connected up the old horn. Looks like I'll need a new relay then. Any particularly good quality ones you can recommend?

[yorkie_chris]

Baphs area of expertise here...

[Luckypants]

The relay is probably FUBAR. They can seize if water gets in them. Best way to check is to listen closely to the relay and press the horn button (with ignitions on, obviously) you should here a click as the relay contacts close. If it is clicking, then relay is probably OK.

Did you fit an in-line fuse to the horn circuit? Have you checked that?

[yorkie_chris]

Maybe take relay apart and try some contact cleaner. If that cures it, put a decent blob of grease around it when you put it back.

[DarrenSV650S]

The relay clicks when I press the horn. And the in-line fuse is fine.
I'll take it apart and have a look

[Luckypants]

Try Chris's bulb test on the relay terminals going to the horn. If it lights, the relay is fine. If that's the case I'd be looking at the fuse and then the earths

Originally Posted by yorkie_chris

Baphs area of expertise here...

Apologies for the delay, I'm staying in Manchester for a few days & just now got internet access.

Originally Posted by Luckypants

The relay is probably FUBAR. They can seize if water gets in them. Best way to check is to listen closely to the relay and press the horn button (with ignitions on, obviously) you should here a click as the relay contacts close. If it is clicking, then relay is probably OK.

Not always the case. Sometimes the coil is perfectly intact, but one of the terminals on the coil also connects to one of the other terminals (usually 87a shorts on to 30) - quite common with water ingress.

Darren, as you stated that the relay output varies between 0 & 4V constantly, the relay is fubar'd & there's little point playing with blubs etc IMHO. Save the hassle & get another relay.

As for recommendations, about the best (and easiest to lay your hands on in a hurry) are the Maplin ones. 12v automotive relay - ask any member of staff & they should be able to put their hands on one in a couple of minutes. If you get one of the staff out on "day release," the code you want is N02AW. That's a 40A 12v SPNO relay, in a pretty water-tight casing.

Other stores stock similar (MotorWorld, Halfords etc etc), but Maplin is the one I know & so far, non of their relay's have let me down.