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Up Topic C1 Information / Repairs - Faults & Fixes / brake light staying on
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- - By twinc1 Date 17.07.19 11:35
my brake light is staying on and after a mile or 2 the battery is dead could be the alternator or is some other common fault …. c1 125 04
Parent - - By p.gill Date 17.07.19 12:22
It could be the nylon rods. Between the lever and the switch is a small nylon rod, about 4mm dia. X about 5mm long, this gets bunged up with crud and gets more difficult to move, remove both switches, if the light then goes out, it’s either one or both nylon rods stuck!
These are very easy to loose! The hole can be cleaned out with a cotton bud and some cleaner, replace without any grease or lubricant.
Parent - - By twinc1 Date 17.07.19 19:17
thanks paul ill have a look but would the light kill the battery after driving a couple of miles
Parent - - By rockstedy Date 17.07.19 20:16
Worth to check if there is no wear grove spot where touching handle. Certainly clean+ graphite grease should help. If not lever need to be replaced or thickened in wear spot with tiny metal plate ( from can of drink) or insulation tape for quick temporary fix. It does happen to me that nearly new handle became temperamental ( brake light stays on) due to wear of cylinder bolt  with  hex screw under holding lever in place due to wear of parts. Greasing that area is one of things which isn’t mentioned in service manual and pain to replace when fail work properly ( can lead to MOT failure). Sometimes other end ends it’s life- micro switch which is easier to replace.
Parent - - By twinc1 Date 18.07.19 06:49
thank rock any idea on the dead battery ….drive a few mile battery light comes on then dead
Parent - - By twinc1 Date 18.07.19 06:51
I was thinking alternator
Parent - - By twinc1 Date 18.07.19 07:04
I need sort them couple problems out get the 4500 mile service done and start using it more or sell is and get my other one up and running that as about 7500 on the clock or sell as is
Parent - - By twinc1 Date 18.07.19 12:59
someone told me if I start the bike and take off the earth lead and it stops its a good sigh the alternator as gone anyone know
Parent - By twinc1 Date 18.07.19 13:09
also took the little plastic rods out and light stayed on
Parent - - By HelmetHair Date 18.07.19 13:11
a fully charged, good condition battery, will last longer that a couple of miles even with no alternator. Try the other battery/alternator tests discussed on this site and see what results you get.
Parent - - By twinc1 Date 18.07.19 14:50
thanks it may have been more than a couple maybe 4/5
Parent - - By HelmetHair Date 18.07.19 19:11
Should do more than 5.
Try the other tests.
Parent - - By twinc1 Date 19.07.19 08:58
I have no testing equipment think I might be better off calling out Mobitec thank for the in put
Parent - - By twinc1 Date 19.07.19 12:18
if it the alternator just got quote £485 parts £360 labour

Parent - - By aware Date 19.07.19 13:54
A not so well charged OR exhausted battery can easily drop in voltage under 8 volts very quickly and then ABS lights go on (dimly), fuel pump struggles to provide fuel etc. At least this is my experience.
Regarding the alternator: You can measure resistance of yellow cables to make sure that the problem is with the alternator or not.
If the alternator is broken either the yellow wires are broken and can be fixed easily.
If the alternator has issue, you may consider recoiling it (DIY or some old mechanic's repair shop)
Next candidate is the regulator. I have successfully installed one for 25 euros and recently found one for 16 euros.
Parent - - By rockstedy Date 19.07.19 14:10
It may be easier to simply check voltage on battery when engine running, yellow cables from alternator. There is plenty info of how to do it on this forum. Can get whole used alternator ( coil) for around 50+new gasket 8+new engine oil and it isn’t rocket silence to replace it on parked bike if comes to worst.
Parent - By twinc1 Date 19.07.19 16:58
thanks guys for all the info will have to get a volt meter and do a bit of home work as im a total novice to fixing scooters
Parent - - By HelmetHair Date 19.07.19 16:47
That’s hilarious. Who quoted that? Elton John?
You might want to invest £3 in a multimeter and do the checks detailed on here.
Parent - - By twinc1 Date 19.07.19 17:04
yeah I thought quote was a bit strong my wife had to get the fan out and give me a glass of water loool that was from pat keenan at Mobitec
Parent - By twinc1 Date 19.07.19 17:12
I've a little guy near me that just recon's  alternator's think he's man if I find a problem with it
Parent - - By HelmetHair Date 20.07.19 09:44 Edited 04.09.19 08:30

It’s VERY unlikely to be a bust alternator. Broken yellow wires perhaps. Most likely bad connection or dead battery.
How old is battery?
Parent - - By twinc1 Date 20.07.19 09:49
new battery
Parent - - By aware Date 20.07.19 10:00
measure battery voltage
1) everything OFF
2) key in ON but not yet started engine
3) engine started

Come back to us with the figures.
Parent - - By twinc1 Date 11.08.19 11:04
then it was 9.7 when I started it again but I've been way since my last post and the bike as been sitting about with the new battery connected if the makes any difference
Parent - - By HelmetHair Date 11.08.19 11:06
Check ALL (don’t stop if you find one broken) yellow wires. The alternator isn’t charging the battery.
Parent - - By twinc1 Date 11.08.19 14:22
thank helmethair would that make the brake light stay on or would that be a separate problem
Parent - - By twinc1 Date 11.08.19 14:50
and what is the best way to gain access to the yellow wire will I need to replace any gaskets as ive never done this before
Parent - By aware Date 11.08.19 19:54
Check visually alternator yellow cables.
If OK, then measure resistance in pairs (3 pairs) and measurements should be the same.
If OK, then regulator is broken.
I replaced mine with a F650 replica for 25 euros, works fantastic.
There is also another good one for 16 euros (haven't tried).

brake lamp different problem.
Parent - - By alunt Date 11.08.19 21:18
The brake light problem sounds like at least one of the micro switches on the handle bars has got stuck. Try pressing the switches in and out and listen for a click, which implies they’re working. Or use your meter to check their continuity if you can get access to their plugs. Replacements are cheap if you look around, but they would need the plugs soldering on. Alternatively BMW will supply them probably at top dollar prices with the right plugs on.

Opening up the alternator to get to the yellow wires is a bit involved and may require a new gasket, but it’s not very difficult. Once in there, repairing the wires will need some good soldering to avoid them breaking again.
Parent - - By aware Date 12.08.19 04:46
If you remove the rear right panel (or remove some screws and lift it enough), you may umplug the yellow cables plug and measure.
In my case, I had almost the same exact figures and it was the regulator that was damaged.
Parent - - By twinc1 Date 12.08.19 13:11
thank everyone will have to open it up and have a look and see how I get on been look on YouTube to see if there was any videos or good pictures but no joy so far
Parent - - By twinc1 Date 27.05.20 13:47
hello guys not been ill for some  time back and ready to sort the bike when I was last on here I was advised to check the yellow wire as I'm a total novice could one talk me through it from the photo I posted .. thanks
Parent - - By HelmetHair Date 27.05.20 14:34
disconnect the plug with the three yellow wires

take OHM (resistance) measurements of the wires heading in to the engine casing WITH THE ENGINE OFF

Check pairs of wires-from top, measure

You will probably find two readings are infinite, which means you can find the broken wire as it will be the numbered wire common to both infinite measurements.

if you pull, push and wiggle that wire/the bunch of three wires close to the engine casing (don't pull too hard!), you may find that they will reconnect briefly and give you a reading same as the one pair that works-and this will confirm the broken wire issue.

Fixing the wiring takes 10 minutes.
Stripping the bike down to get access takes the time! Its a good opportunity to change the oil if you havent done it for a while.
Parent - - By twinc1 Date 27.05.20 15:28
thanks HelmetHair I will get a test meter tomorrow and have ago still all a bit Greek to me but I'll see how go failing that I will have to find someone with the skill knowledge and time on their hands to do the job who is not asking ridiculous money to do it
Parent - By HelmetHair Date 27.05.20 19:20
just a normal bike mechanic can do this stuff.
Your last quote was ridiculous. Its, possibly, a two hour job start to finish-as youve already got that panel off-and the altertantors dont break, just the wiring, just where it goes through the engine casing.
Parent - - By BOR Date 28.05.20 14:22
Before you go too far..........

My battery wsn't charging and the bike was going haywire.

I replaced the voltage regulator ( the thing with cooling fins in your photo) which cured the problem.


I am still suspicious, that the connector pins simply had a layer of electrolytic corrosion on them.

Try disconnecting the connector in your photo, and cleaning up the pins (if possible).
Parent - By twinc1 Date 09.07.20 09:27
thank BOR i'll give the pins a clean to
Parent - - By twinc1 Date 09.07.20 09:24
you was right HelmetHair one of the yellow wires was broken just at the engine case is it best to get a new gasket before taking the case off
Parent - - By HelmetHair Date 09.07.20 10:26
If you are careful, you can remove the gasket whole, and use a blade to cut it off without damage. Any small damage can be repaired with gasket sealant, but clearly a new gasket is (1) best
(2) safest.

So, the answer is, do you feel lucky?
Parent - By twinc1 Date 09.07.20 17:59
where is the best place to buy a gasket lool
Parent - - By twinc1 Date 20.07.20 15:00
exhaust is off ready to take casing of is best drain oil out first
Parent - - By HelmetHair Date 20.07.20 15:21
yes. Absolutely.
Parent - - By twinc1 Date 21.07.20 10:04
ok everything off 3 wires going into the alternator case 2 are broke but they are both yellow how do i tell which go's to which ....... stumped :-/
Parent - By twinc1 Date 21.07.20 10:08
all 3 are yellow to be accurate
Parent - - By HelmetHair Date 21.07.20 10:18
It should be obvious from the length and position of the wires-or the pattern of the break on the outer covering.

Bit of detective work needed!
Parent - - By twinc1 Date 21.07.20 11:39
just looked at it and  the wires do seem to sit better in certain positions  .......... but there is a guy across the road that reconditions alternators is there a electronic test he could do to make sure which is which
Parent - - By twinc1 Date 21.07.20 12:03
and what will happen if i get them round the wrong way
Parent - - By twinc1 Date 21.07.20 16:31
someone it don't mater if you get them the wrong way round anyone know different
Parent - By twinc1 Date 21.07.20 18:26
well wires are soldered think the hardest part we be getting a gasket off BMW
Parent - - By HelmetHair Date 22.07.20 08:42
Am pretty sure that's right, as the C1 system takes all the voltages in to the rectifier unit at the same time.
Up Topic C1 Information / Repairs - Faults & Fixes / brake light staying on
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