Hi all, I was riding to work today with everything as normal and then suddenly the alternator/charging light came on. I pulled into a layby and gave it a few revs to see if it would clear, but it didn't. I then turned it off and on again thinking it might clear/reset itself but instead I was greeted with a dead bike! Arf. After staring at it for a bit and turning the key a lot I asked someone for a push and thankfully it bump started and got me home.

Fiddling with it on the driveway I get the following things working/not working with the ignition turned fully on:

Working:

• Sidelight, headlight
  
• Tail light
  
• Indicators
  
• Horn
  
• ABS, blinks and the relay clicks and clickety-click bzztt's like it always did if that is the ABS
  

Not working:

• Starter button - no clicks, no churns, no fuel pump, no nuffin'  
  
• Alternator light (this usually comes on before it starts, right?)
  
• Oil pressure light
  
• Neutral light
  
• Bulb check light
  
• Brake light for either brake
  
• Fuel gauge
  
• Gear indicator (I do remember this was flickering as I was riding it back home, didn't check anything else.. Just wanted to make it back!)
  

So where do I start? Fuse box? A quick read up suggests the ignition switch can cause big hassles but the ABS light works every time and the lights that work do not flicker, so I'm not convinced it's that. Alternator brushes perhaps, but I have a receipt for the alternator being refurbished with new brushes not long before I bought the bike about 2.5 years and ~12K miles ago.

Help please :pale:

Checking fuse #1 would be a good start.
(All that doesn't work is protected by fuse #1)

Inge K. wrote:Checking fuse #1 would be a good start.
(All that doesn't work is protected by fuse #1)

I had that happen last year, in a totally dark place. Leaving a function in a rural house and last man to leave, everyone gone and no mobile signal either. Fuse cured it. As in had a spare fuse.....

Ahhhh, that gets you home, wondering all the way why the fuse blew in the first place.

brickrider2 wrote:Ahhhh, that gets you home, wondering all the way why the fuse blew in the first place.

When it happened to me on a ride to work, I lost all indication as listed above (including speedo and, I think, rev counter went to zero). I recall battery light came on and stayed on and I was worried that it was an alternator issue. 

However, as IngeK says, fuse no 1 was the culprit. 

I didn't stop the bike until I got to work (just in case it wouldn't restart) and, in a quick investigation, I discovered that the rear brake light bulb had blown - I reckon this was what caused the fuse to pop. Replaced bulb, replaced fuse and no problems since.

And lo, it was indeed fuse #1. Why can a silly secondary fuse allow you to be stranded? Seems a strange way to wire up a vehicle!

And brickrider2 has it right, why did it blow? It's not the first fuse to have gone either, I had to replace #8 a while back as the indicators went mental and the horn stopped working. There was no reason for that, and there appears to be no reason for this - as far as I can tell everything is working fine. And I'm clearly not on my own, everyone's replacing fuses all over the place.

I will now carry spare fuses with me at all times, and live in general fear. Thanks BMW! At least it wasn't anything major

Ah yes, but just remember this.
Do you realise how cool you look to other people/riders/old car owners when you just pull your stopped bike over, shrug, take of the side cover, reach into your pannier and pull out a fuse, and away you go.
It happened a few times to me, and after the first time I was pretty relaxed. 
Eventually of course you have to find the problem, but meantime, chill.

I reckon riding an old K-bike keeps us ol' gray-haired types alert and observant  

Be glad we don't use the older glass tube type fuses....

I have swapped to the blade type on my 2 RD350's because they don't last.

Manufacturers use fuses to protect wiring from too big a draw which can melt insulation and damage components...

I would be very surprised if any fuse lasted as long in a motorcycle as they do in a car - type for type.

I'm sure the range and ampliude of vibrations have a direct bearing on metal fatigue...

I guess we just have to remember simple electric theories

as corrosion sets in and contact area becomes smaller on fuses and fuse holders or any electrical connector  , contact point current increases dramatically  , some voltage drop accompanies this also .


we do remember stuff like.... don't start the bike with a flat battery ..because the contacts might weld together ..but some of us seem all too willing to forget about anything else of a similar nature .

it isnt rocket science ...

good maintenance is just that  and if we let things corrode away through electrolysis, vibration  and corrosion without doing something about it ...the expectations are as clear as the outcome .

many of us stick with the old beemer because the owners are prepared to do what others wont ,

bmw made an exceptional bike , with all its fantastic design and engineering , lasting well beyond its design life span

Anybody who's had a Guzzi will remember the problems with their 'Continental' type fuses. You forgot to roll them through 360 degrees once a month at your peril. Once you'd done that a sufficient number of times the end caps fell off anyway.

All mine have blade fuses

yeah seen that before too dai

laughing my head off with memories of an old lucas fuse block on the mighty "Steve Austin"  austin 1800 great car but typical electrical design issues   only ever beaten by the any of the  Rover v8s you could care to mention .... the electric windows were a farce and the switches ...well its lucas
designed in obsolescence
giggles

Yes Charlie and the Austin 1800s had positive earth electrics just to be different to the little brother the Mini.

Dai wrote:Anybody who's had a Guzzi will remember the problems with their 'Continental' type fuses. You forgot to roll them through 360 degrees once a month at your peril. Once you'd done that a sufficient number of times the end caps fell off anyway.

Ha!

Okay, I just tried to go for a test ride and didn't make it off the driveway. Everything was working fine until I started it, starter churned like normal and everything was fine for about half a second after the engine fired up, then the fuse blew again. What changes on this circuit when the bike is running?

Fuse #1 gets power when the key switch is turned to ON and the kill switch is in the RUN position, that power is labelled as '15' in bosch schematics.

The circuits that are energized thru fuse #1 include:

Bulb Monitoring Unit
Clutch Switch
F Brake Switch
R Brake Switch
Instrument Cluster (Gear Display)
Heated Grips
Additional Equipment Connector
Additional Instrument Connector

So something in one of these circuits is likely shorted to ground and causing the fuse to blow.

The starter won't engage without '15' power passing thru either the clutch switch or the IC (with Gear in N) to the start button and then to the starter relay when the button is pressed.

check the front brake switch ...just a suggestion

charlie99 wrote:check the front brake switch ...just a suggestion

The front brake switch works fine when it hasn't blown the fuse. I didn't have time to try it (or anything else) when the engine started. It was literally thumb starter, oh good it's running, oh no it's blown again Before it was running everything worked a treat.

Are the heated grips "activated" when the engine is running? Or is the engine running total coincidence and it shouldn't affect anything at all on this circuit? I've tried looking at the wiring diagrams but 'kinell they are so very complicated!

I shall take the tank off and have a root around, as well as under the switch pad thing and anywhere else around the front with wires coming out of it. Thanks all for the help so far. Also the extra temperature gauge has always been temperamental and hasn't worked for a while, I'll check that out too.

Snod Blatter wrote:......Also the extra temperature gauge has always been temperamental and hasn't worked for a while, I'll check that out too.

Try disconnecting the 'special equipment' connector in the electrical box. If the fault clears, it could be the gauge has a dead short or the wiring to it has shorted to earth.

Also, with ignition ON - not started..... Do you have tail light and brake light?

Holister wrote:Try disconnecting the 'special equipment' connector in the electrical box. If the fault clears, it could be the gauge has a dead short or the wiring to it has shorted to earth.

Also, with ignition ON - not started..... Do you have tail light and brake light?

I shall give that a go, thanks!

Tail light and brake light work fine when the fuse is intact, I can play with the brakes as much as I want and the light is always bright and solid, no flickering. Tail light is similarly solid. Everything worked perfectly until I started the engine and it suddenly didn't work any more.

If nothing changes when the engine is started then it must be the act of me sitting on the machine or the vibration caused by the engine, both point to worn away insulation on a wire somewhere. But before I can really start with this I need to stock up on 7.5A fuses

If I stick a multimeter on the left fuse contact the resistance between it and ground (a frame bolt) is 1 ohm - surely this isn't right? Moving the bars lock to lock didn't change it though.

Snod Blatter wrote:
If I stick a multimeter on the left fuse contact the resistance between it and ground (a frame bolt) is 1 ohm - surely this isn't right? Moving the bars lock to lock didn't change it though.

That's a great check there--you have a way to find the fault without blowing a ton of fuses.  1 Ohm is a short somewhere, so you can go thru the circuits to disconnect items until you find the culprit.  Does your meter have a beeper/continuity checker--if so you can search until the annoying noise goes off...

Do you have heated grips--maybe check those wires at the switch. 

If i were doing this i would pull the tank and start at the back of fuse #1 and trace and shake the harness of the green/black wires in the circuits listed.  Commence to jigglin', and Good Luck.

kennybob wrote:That's a great check there--you have a way to find the fault without blowing a ton of fuses.

Thanks, I thought of it myself

No beeper but the numbers should suffice. If anyone would be so kind as to check their own bike for resistance between the left fuse contact and ground (I'm using a big allen bolt in the middle of the side of the bike) it'd be much appreciated, I'd like to have a number to aim for.

I do have heated grips, this bike has all the bells and whistles. I have read that they can cause trouble and the previous owner replaced them so it has all been messed with, I shall pay particular attention to them. They are not switched on though.

Right, to the tank!

Snod Blatter wrote: to check their own bike for resistance between the left fuse contact and ground

i don't have heated grips nor any accessories or additional instruments, and measured 7.3 Ohms on a K75S.  The schematics look identical.

Thanks, kennybob. I am seeing 8 ohms at all times with everything off, and can't seem to make it go back down to 1! I have the tank off and nothing is jumping out at me, the brake switch wire looks to have melted its insulation on whatever the heatsinked thing is right under the headstock but no wires can be seen and there is no short there until I pull the brake lever. Also if I turn the heated grips on the resistance drops to 5 ohms, so that seems to be working fine.

There is also a pair of yellow wires which have heated up their connector block to near-melting and slightly blackened the wires but again no short and no visible wire under the insulation. Measured with the multimeter shows no short.

Disconnecting everything I can find keeps the resistance at exactly 8 ohms, but at least I know this is now where it should be. I'm still lost and seemingly cannot replicate the problem but I haven't uncovered all the wiring around the headstock and under the switch pad just yet. I may investigate more after the last episode of Top Gear which is on right now

Snod Blatter wrote:There is also a pair of yellow wires which have heated up their connector block to near-melting and slightly blackened the wires but again no short and no visible wire under the insulation.

That's most likely your problem. Where do they go? Clutch or front brake? Or rear brake?

That heatsink looking thing is your Ignition Control Unit, a very important piece of gear.  Surprising that it would get so hot as to melt insulation of a wire laying near or across it.

The two yellow wires could be the choke indicator from the throttle body to the Instrument Panel, but more likely the clutch switch wires.  i would be concerned about any connector block being discolored or melted--that would be a place to investigate in detail.

Maybe pull the bulb monitoring unit and see if it will start and run without blowing a fuse--it has transistors and active components in there that could short.  Haynes manual indicates a way to check it by removing bulbs, but i don't think it would work for a shorted device.

Dai wrote:That's most likely your problem. Where do they go? Clutch or front brake? Or rear brake?

It's the clutch switch. The contacts are blue with corrosion, I guess that is what is causing the heat. I don't remember managing to pull the clutch in before the fuse went but it's possible and I'm quite sure I didn't play with it when the engine was off and everything seemed to be working perfectly, and the fuse wasn't blowing then... I'll clean up the contacts and try again when I have bought some fuses.

The melting insulation on the front brake switch wiring may be from lots of vibration rather than outright heat from the ICU, it's hard to tell. I shall clean all the green/black wire contacts and then if I'm not getting anywhere will take the flippin' tank off again (I wish it was easier) and disconnect the BMU. Plenty to go at now but a shame the problem wasn't staring me in the face the moment I lifted the tank off, I really hoped it would be obvious. Oh well.

Again, many thanks to all for the help so far.

That ICU unit is rubber mounted, open the 2 nuts and it slides back and out but you kind of have to pull some of the loom wiring to each side. It went wrong on my 92 [91 build] K100LT and replaced it. It cause erratic problems of non start nature. £50 Motorworks at the time. But a dodgy plug connection to it will also produce a similar effect.

On the 8v engines as far as I know the clutch switch, front and rear brake switches are all the same part. They are on the 84K100 because I had them off and replaced them. Same on my LT. Its worth know if you are travelling and the clutch switch goes wrong, swap the one from rear brake and sorted. You will still have brake light from front brake.

But a dodgy clutch switch will only cause a non start [everything else should function correctly, lights and accessories]. Been there when I changed the bars on the RT and pulled a little too hard on the switchgear. Neutral light on will allow you start irrespective of the clutch switch but that means finding neutral. Not sure what's on your K but my LT has a side stand pull up mechanism worked by the clutch cable. I have a feeling some have an electrical side stand switch.

I have no side stand switch (I think a previous owner removed it?) and no stand pully-uppy cable doodads either, I can (and have..) ride away with the sidestand still down.

As an aside there is a small wire which is bolted to the outside of the right hand switchgear near the brake switch, it has a metal loop on the end of it and the bolt goes through. This wire looks as if it has led a hard life at some point, but again it may just be the insulation coming away due to age. Am I right in thinking this is just an earth wire so cannot be shorting out on the bodywork?

Fuses will be bought on the way home from work tomorrow, borderline excited to see if the contact cleaning has cured it [insert praying emoticon here]

That wire is for earthing as you say, otherwise it will try to earth through the throttle cable and cause problems.

If you had a side stand switch then my take is removing it meant someone had to short out the connection so the bike thinks the side stand is up all the time. A bit like cutting the plug off the clutch switch and then connecting the 2 wires and refitting it. Check where that side stand switch attaches to the loom in case that was done and has come apart.

If the ICU has had 12v applied to its outer case then that may well be the problem and that one or some of the components have been damaged.

As long as you have the tank pulled back or off, might as well clean and lubricate all the connectors you can see or reach--if you have blue corrosion on one pair it could be in any of them considering the age of the wiring. 

Also undo the bolt to the frame holding that big bundle of brown ground wires and clean all the terminal ring lugs and the mounting boss on the frame.  A clean ground is a good ground.

Just to be safe and avoid any arcing it is recommended to disconnect the battery negative terminal cable first to open-circuit the entire bike.

It sounds like you are very close to getting this sorted--way to go!

That non working list set me thinking about the connector block/plug to the clocks. They all need that except the starter button. But the starter button needs the neutral light to function which it hasn't got. Just a thought as it seems to be the same effect as if the clocks are removed and the K dont go without clocks.

kennybob wrote:As long as you have the tank pulled back or off, might as well clean and lubricate all the connectors you can see or reach

Way ahead of you. I have also cleaned the common ground, all this cleaning has lowered the resistance between the left fuse contact and ground from 8.1 ohms to 7.6 ohms. Progress.

I bought some fuses on the way home, played with the bike with its tank off and everything seems to work perfectly. I can sit on it, I can move the front lock to lock, everything's great.

I push it off the hilly driveway (oh god my arrrmmmsss) and decide to video what happens to show you all that either I am a clever boy and have fixed it or that this is not a normal reason to be blowing fuse #1. Sadly it was the latter. Check it:



The talking is me, my dad and an old bloke who walks his dog past the house, he likes to see what's going on As you can hopefully see, everything works perfectly until I start it. Then poof, blown fuse.

Halp BMU next?

Change the ICU. Gut feeling I reckon there is a component that heats up fast as soon as you start is and then goes short and blows the fuse. I may well ba wrong so borrow an ICU to try.

Good Video--seeing is believing,
Are these normal for your bike:
Why is the red fuel light blinking?
Why doesn't the choke light come on the IC when you flipped the lever?

i hope it is the BMU, the ICU is upstream of fuse #1 so it doesn't seem likely to be able to blow the fuse, plus the bike was still running even with the fuse blown?

What is that additional instrument on the right inner fairing?

Red light is the ABS light and an 89 RSSE does not have a choke light.
I agree it wont be the ICU.

The choke light hasn't worked during my ownership of the bike, and the fuel light blinks as part of the ABS - it all stops flashing when past 4MPH or so. The right inner fairing has the temperature gauge that doesn't work, the left has a fuel gauge which does work - as far as I know the fuel light itself doesn't work, it has never come on even though I've very nearly ran the tank dry a few times.

The bike runs fine after this has happened, I just can't start it. To me it looks like some strange problem with the clocks or charging system but my mind doesn't have the wiring schematic for these bikes burnt into it

Right, BMU.. I have three fuses left so it's worth a go! Oh and I'll twist the throttle a bit too in case it's the TPS, the fuse blew as soon as the switch was off its stop..

RicK G wrote:Change the ICU. Gut feeling I reckon there is a component that heats up fast as soon as you start is and then goes short and blows the fuse. I may well ba wrong so borrow an ICU to try.

When you start up the Hall Sensor signal immediately kicks in. Fuel pump gets an initial signal when you press the starter button. But to stay running it gets a different signal, from the HES. As mentioned this could be a fault in ICU too that kicks in when the HES signal kicks in. The wiring from the HES comes up behind the radiator to a connector under the tank and can also be damaged.

Jack - PM me. I'll send you an ICU for testing.

92KK 84WW Olaf wrote: The wiring from the HES comes up behind the radiator to a connector under the tank that looks the same as the connector for the front brake/clutch switch and I discovered could be confused.

Rather difficult to mix the HES connector with any other connector as it isn't a
similar connector on the entire bike.
The HES connector have five flat pins, the brake/clutch/choke switch connector
have two round pins.

Inge K as usual is correct. My mistake. Will amend the post. Brake and clutch connectors can easily get swapped...

Does it only happen when you touch the throttle grip? --would it continue to idle longer had you not tried to rev it up, or does it always blow within a short time after starting regardless of throttle contact?

Has it ever been dropped over onto the right side and smacked the end of the grip?

If yes to any of these, then try disconnecting the heated grip connector and see if it will run.  If not then on to something else.
 
To say it continues to run, but you can't start it after this happens only means that fuse #1 has blown.  Fuse 1 is required to be in the circuit for starting but not for running, which is why you could bump-start it to get home.


Another idea, Could it be that the 2 yellow wires from the choke position have been switched with the 2 yellow wires for the clutch switch?  They both use the same style connector and are both routed on the left side frame tube under the tank.

Remove the fuse and hook up the ohmmeter trick again on the left side to ground--8 Ohms.  Then engage the clutch and see what happens, then engage the choke and see, then shift gears out of N and see if anything chances, etc with each of the circuits on fuse 1.

Since you say the heated grips have been changed and messed with by the PO, then it makes you wonder about that circuit also--grab the grip and see if the resistance changes.  The switch may be on the ground leg of the grips such that the element has +12v on it all the time and touching it pushes something internally to ground it out?

You are all gentlemen and scholars, but I have been given a gift - the gift of the second fuse giving wiring and whatever else enough time to break properly and cause me a permanent short that I could trace. I came back to the fuse box with my multimeter and was inordinately pleased to find it reading 1 ohm to ground - this meant I could just disconnect things until it went back to 8 ohms. I quickly found this to be the culprit:



Something I would call a molex connector. It has also badly affected this small blue single pin connector:



But whatever it connects to doesn't seem to be shorting to ground. What is that?

Anyway, the molex connector makes the resistance from fuse to ground 1 ohm whether the blue connector is together or separated, so it's definitely the molex. And, unless I'm very much mistaken, this leads straight to the fuel gauge and temperature gauge on the inner fairing.

Playing with the multimeter again I find that the short is not from the green/black wire to the frame bolt, so wiring shorting on the frame is not the problem - more poking and it's 1 ohm from green/black to brown on the gauge wiring itself. Did I mention that the temperature gauge has not worked properly for a while and was sold as being a bit dodgy when I bought the bike back in February 2014? I think you can see where this is going..

I unplug the temperature gauge and the short goes away. I hate you, temperature gauge. I hate you so much. Now, to put it back together again and see if I have caused any other damage..

Looks like the temperature gauge was raising your temperature! But its always a feeling of satisfaction to have found the culprit.

Snod Blatter wrote: It has also badly affected this small blue single pin connector:
But whatever it connects to doesn't seem to be shorting to ground. What is that?

It's the connector to the sensor for your temp gauge.

And so, with the temperature gauge disconnected (and removed because it's toxic!) she runs a treat again. Proof:



I even took it round the block after this, everything works like normal. I'll take the gauge to bits if I can and see what's going on inside, but it can wait a while..

So, many thanks to all (and particularly Dai for offering help that would require him to leave his computer, and kennybob for measuring his own bike's resistance) but there are still things I don't understand - why would this only happen when the bike is running? Is it just coincidence or the rise in voltage from the charging?



Edit: Ahhh that makes sense, thanks Inge. I feel even better knowing that is so non-critical too.

Snod Blatter wrote: still things I don't understand - why would this only happen when the bike is running? Is it just coincidence or the rise in voltage from the charging?

When you take it to bits you'll find the problem, but basically there are a few points to consider.

The temperature sensor and gauge work together as a series resistance to give an indication of the temperature.  There is a heater wire in the gauge (resistance ~20 Ohms) that is wrapped around a bimetallic spring such that when current flows in the heater resistance it will cause the gauge needle to move and point at the calibrated scale numbers.  This is where the +12v enters the circuit.

The sensor is an NTC device, meaning negative-slope temperature coefficient, in that the resistance is higher when cold and decreases to a lower value as it heats up (which is opposite behavior to most metals).  So as the engine warms up the sensor resistance decreases, which lowers the resistance in the series circuit with the heater causing more current to flow to heat the spring and move the needle.  The hotter it gets the higher the current and greater the spring deflection.  The sensor completes the circuit with the return path back to ground.

In your bike the temperature sensor likely appears as a high resistance (greater than 5k Ohms) when cold but changes immediately to a very low value (less than 1 Ohm) once it warms up even slightly (the sensor is defective).  And by now the heater wire inside the gauge is likely broken and shorting thru the bimetallic spring.  So when the engine is cold the circuit has high resistance and the fuse is okay for starting, then as it heats up it quickly completes a very low resistance path to ground thru the sensor wire and the high current is too much for the fuse. 
cheers, kenny

kennybob wrote:When you take it to bits you'll find the problem

Yup. I finally got round to taking the clock to bits, and as soon as I took the plastic cover off the back the problem was obvious - the green/black feed wire had broken off and was waggling about looking for things to short on!

Where the wire is, and where it should be.. Looks like a combination of fatigue and corrosion allowed it to come away, the rest of the connector is still riveted to the clock. No problem, sand the bit on the clock until it's clean(ish) and then soldering iron ahoy!

It now works again, and I haven't blown any more fuses. Though it doesn't read very high, only makes it a bit out of the blue when it used to read in the middle. Maybe the replacement K1100 radiator works better, or just isn't full of crud? Or perhaps more connections are corroded and it's keeping the voltage down. I dunno.

This clock stopped working in the Black Forest nearly two years ago, and it chooses to make itself known now? Bizarre. But I'm glad it waited! I'm planning on taking the K to Germany/Luxembourg in about 8 weeks time, I'll check the fuel gauge for similar problems before leaving and stock up on fuses to take with me.. And make a note to take a multimeter. That way I won't need any of it, right??

I like your thinking, take a spare or tools and the problem will not appear again. It is amazing that a "little" thing like that can cause so much heartache.

ainsjac wrote:I like your thinking, take a spare or tools and the problem will not appear again.

True... very true.
Been stuck on the road only once, apart from a puncture. Couldn't get the key to turn in the ignition after I filled up with petrol. I didn't have a screwdriver small enough to get at the tiny screw to remove the key mechanism from the ignition switch and had to walk some distance to buy one. Had everything else.


I am convinced that if I'd had a small screwdriver in my kit, that ignition lock would not have failed.