Horny issue!

Hi BMWST Communtity users (it's been a while!)

 

I've lost me horns!

 

And I'm just about frazzled and out of ideas, having been tinkering away all of today.

 

I think the left hand switchgear horn switch is duff. However, all other switches fine on that side.

 

The bikes a 2002 single spark with the twin Bosch horns (UK spec).

 

What I've tried to check

 

I have a 12v supply at the fuse and relay. Have swapped the relay, nothing. Also the fuse is good.

 

The horns have the 2 wire cable feed - brown (earth?) and green/grey (live) with the tiny recessed pin socket connectors. I've tried to check for a 12v supply between either of the female connectors and battery earth, but cannot get a reading.

 

Have dismantled switchgear, overdosed it on contact spray and reassembled, still nowt.

 

It looks like the live feed from the ignition switch goes to a junction block up under the left hand side of the instrument panel and the horn switch wires also go to this block??

 

I'll be damned if I can get my mitts in there to separate the terminal block and check for corrosion.

 

The cable sheath that houses all ignition and other wires along/under the support frame in front of the headstock is cracked/perished, but I cannot see any obvious broken/bare wires!

 

What have I overlooked or failed to check?. I only have a multimeter to hand (no test lamp) as away from home.

 

Thanks in advance for any pearls of wisdom. An internet search hasn't thrown up anything close.

 

Cheers

 

Martin

Morning Martin

 

When it comes to testing things like horn circuits a test light is sometimes more useful than a voltmeter. (I know you don't have one but they are easy to build)

 

In any case, on to your problem--

 

With the key turned on can you hear (or feel) the horn relay click when you press the horn button? This a good first step as it tells you what side of the horn circuit to look at for the problem.

 

If no relay click then your problem is in the relay to the handlebar switch circuit or no 12v power to the relay switching side.

 

If the relay clicks then your problem is from the relay to the horns or lack of 12v power to the output side of the relay.

 

The horn relay socket in the fuse box should have (2) 12v power inputs.

 

Terminal (1) at the relay gets it's 12v power from the #4 fuse.

 

Terminal (3) at the relay gets it's 12v power directly from the ignition switch.

 

Terminal (5) at the relay should go to ground when you push the horn button.

 

Terminal (2) at the relay goes to the horns & should show 12v power when the relay clicks.

 

Edited July 24, 2017 by dirtrider

Hi DR

 

Many thanks for your considered reply and at such an ungodly hour! That's really good of you. Following your advice.

 

To clarify - with the ignition on I have 12v at both terminals 1 & 3.

 

Whilst it feels like the relay is clicking, I think that it may instead be the load relief relay when ignition switched on. As nothing at all when horn button pressed.

 

So we're saying a bad earth, broken wire or the switch itself on the horn switching side of the circuit then?

 

Anyway to pinpoint it without just buying a new left hand switchgear gear assembly?

 

Thanks once again.

 

Martin

Hi DR

 

Many thanks for your considered reply and at such an ungodly hour! That's really good of you. Following your advice.

 

To clarify - with the ignition on I have 12v at both terminals 1 & 3.

 

Whilst it feels like the relay is clicking, I think that it may instead be the load relief relay when ignition switched on. As nothing at all when horn button pressed.

 

So we're saying a bad earth, broken wire or the switch itself on the horn switching side of the circuit then?

 

Anyway to pinpoint it without just buying a new left hand switchgear gear assembly?

 

 

Morning Martin

 

Not a real pinpoint but maybe an area.

 

With key turned on put your voltmeter between terminal (5) & terminal (3) in the relay socket. Now push the horn button.

 

If the meter shows 12v when you push the horn button then that side of the circuit is operating correctly.

 

If no voltage when button pushed then you will have to determine IF the wire between the relay socket & push button is open, or if the switch itself is bad, or if the ground side of the switch is open.

 

Added: if the L/H side turn signal switch operates OK then the ground circuit to the L/H handlebar switch unit is probably working good (this is a quick ground circuit test).

Edited July 24, 2017 by dirtrider

Thanks again.

 

With the relay out I have 12v across terminals 3&5. Pressing the horn button has no effect - still 12v. I tried to measure the voltage also between earth and the horn socket (tiny recessed square socket holes) but could not get any voltage reading with the horn button pressed.

 

Would it be worth removing the silicone on the bottom of the horn micro switch and doing a continuity test - switch open/closed?

 

It's driving me mad ahead of an MOT test fail if not sorted.

Edited July 25, 2017 by die_panzer

Thanks again.

 

With the relay out I have 12v across terminals 3&5. Pressing the horn button has no effect - still 12v. I tried to measure the voltage also between earth and the horn socket (tiny recessed square socket holes) but could not get any voltage reading with the horn button pressed.

 

Would it be worth removing the silicone on the bottom of the horn micro switch and doing a continuity test - switch open/closed?

 

It's driving me mad ahead of an MOT test fail if not sorted.

 

Morning Martin

 

If you have 12v across terminals (3) to (5) then your horn should be sounding all the time with the horn relay installed. (so this reading doesn't make sense)

 

Are you sure that you are measuring across terminals (3) & (5)?

 

This is why I like using a test light for this sort of circuit testing. It takes some current for a test light to light up bright.

 

Would it be worth removing the silicone on the bottom of the horn micro switch and doing a continuity test - switch open/closed? -- ONLY if you positively determine that the horn switch is the cause of your problem. So far we haven't determined this.

 

If you have 12v across terminals (3) to (5) then your horn should be sounding all the time with the horn relay installed. (so this reading doesn't make sense) sorry that was with the relay removed!

 

Are you sure that you are measuring across terminals (3) & (5)? How do you get access to the connections below the relay?

 

This is why I like using a test light for this sort of circuit testing. It takes some current for a test light to light up bright.

 

Would it be worth removing the silicone on the bottom of the horn micro switch and doing a continuity test - switch open/closed? -- ONLY if you positively determine that the horn switch is the cause of your problem. So far we haven't determined this.

I probed in the silicone and got continuity when pressing the switch! So that suggests it's ok. Also continuity between the switch (brown/yellow) wire and where it meets junction block under the instrument panel. Also between switch and back to relay.

 

So am I right in now thinking it's between the relay output and the horns - presumably before the wire (green/grey) meets a connector to feed each horn separately?

 

So am I right in now thinking it's between the relay output and the horns - presumably before the wire (green/grey) meets a connector to feed each horn separately?

 

Afternoon Martin

 

That would seem logical-- BUT!-- If the switch has continuity back to the relay & the relay has 12v power then you should be able to hear (of feel) the relay click when you push the horn button.

 

With relay removed IF you jump terminal (1) to terminal (2) in the relay socket do the horns sound?

Edited July 25, 2017 by dirtrider

Hello again DR and thanks for your time and patience in trying to help solve this problem.

 

Have just tried to jump pins 1&2 with a paper clip and still 'niet, nada or sweet little else' I'm afraid to say!

 

 

Hello again DR and thanks for your time and patience in trying to help solve this problem.

 

Have just tried to jump pins 1&2 with a paper clip and still 'niet, nada or sweet little else' I'm afraid to say!

 

 

Afternoon Martin

 

Well, then that kind of points to an open between terminal (2) & the horns or, or bad horns (possibly full of water), or an open ground circuit to the horns.

Morning DR!

 

So, I have shorted sockets 3 + 5 in the fuse box (horn relay) and that gives me the horns.

 

With ignition on, I also have 12v at socket 1.

 

So, as you quite rightly say, that points to either a bad earth on switch or a break between switch and relay.

 

But, where is the earth connection for the switch (if it's shared with other components, then would they not also play up?)

 

And how do you even begin to sort the feed out from the switch to relay? Would you simply piggy back in a separate wire? If so, is there any easy way to get access under the fuse box (or that part of it?)

 

Feels like I'm closing in, but there's still a lot of work to be done!

 

Terrific support from you so far, by the way.

 

Martin

 

 

 

 

 

Morning Martin

 

So, I have shorted sockets 3 + 5 in the fuse box (horn relay) and that gives me the horns.--This is VERY PUZZLING as terminal (5) goes to the switch not the horns. Are you sure that you have properly identified the socket terminal numbers?? (it seems that what you identify as socket terminal (5) is really (2)

 

But this does shows that the circuit between relay socket & the horns is working. But horn circuit should be terminal (2)

 

With ignition on, I also have 12v at socket 1.--This is puzzling as yesterday you wrote that the horns didn't sound when you shorted (1) to (5).

 

So, as you quite rightly say, that points to either a bad earth on switch or a break between switch and relay.--See above, the horns are not powered from terminal (3) so powering from (3) only confirms that terminal (2) to horns circuit is good & terminal (3) is getting 12v power.

 

But, where is the earth connection for the switch (if it's shared with other components, then would they not also play up?)--If the L/H turn signal switch is working then the earth connection to the L/H switch is probably working OK.

 

And how do you even begin to sort the feed out from the switch to relay? Would you simply piggy back in a separate wire? If so, is there any easy way to get access under the fuse box (or that part of it?)--You need to identify the circuits better before running any additional wires.

 

SO, lets identify & confirm the circuits ----

 

 

First, make a large diagram of the relay socket on a piece of paper.

 

Next- Place the voltmeter black lead on a clean earth connection.

 

Now with "KEY OFF" probe all the socket terminals with the voltmeter red lead- One terminal should show 12v (that is terminal (1) -- Label that as (1) on your paper drawing.

 

Now turns KEY ON & probe the remaining socket terminals one more should NOW show 12v (that one is terminal (3)--Label that as (3) on your paper drawing.

 

Now turn key off & move your voltmeter red lead to the battery (+) post. Then probe the remaining relay socket terminals as you press the horn button. One relay socket terminal should flip between 0v & 12v as you press the horn button-- Label that as (5) on your paper drawing.

 

The remaining terminal should be the one going to the horns-- Label that as (2) on your paper drawing.

 

Once you have ALL the socket terminals properly identified--

 

Use a wire & short terminal (1) to terminal (2) -- DO THE HORNS SOUND?/ If YES then terminal (1) & (2) are working correctly & horns work OK.

 

If the horns don't sound in the above test then with "key on" short socket terminal (3) to terminal (2)-- Do horns sound?? If so then you probably have a power supply problem to terminal (1) --probably in the #4 fuse area.

 

Then with key-on hook your voltmeter probes between relay socket (3) & socket terminal (5)-- Voltmeter should toggle between 0v & 12v as you push the horn button. (yes/no)

 

Hello again DR

 

Because I'm off on tour in the morning, I wanted to get the horn operational - I figure that I usually have more need of it in France than England!

 

Anyway to confirm as per terminal posts identified on the bottom of the relay itself.

 

A short between 3 & 5 gave me the horn without use of the button switch.

 

I was registering 12v at terminal 1 also.

 

I did not have continuity between the switch and terminal 2 (or any terminal) which suggested a break somewhere there - although I could trace continuity from the switch back to the plug socket up behind the instrument panel and to the left hand side (brown/yellow wire)

 

So (ahead of seeing your latest reply I must say and with time ticking down) I opted temporarily to feed a new wire between the relay terminal (post 2) and a now cut wire at the plug socket (instrument panel).

 

It's a bit 'Heath Robinson' but all appears to now be working as it should.

 

With more time, I would like to try and trace the break in the wire more carefully - but at least for now I should be able to get away on tour and return to get the bike MOT'd.

 

You though Sir, have been an absolute gentleman in attempting to walk me through the problem. It's been too long since I did anything even remotely electrical! Huge praise once again dear fellow