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Discussion Starter · #1 ·
Hoping this is the right section to post this.
Ok important details:
My bike is a Brand new Yamaha xenter 125 (2017 edition though the manual online for the 2016 edition is identical to my physical manual)
fuses for the bike:
main fuse 20a
ignition fuse 7.5a
signalling 15a
headlights 15a
backup 7.5a

Long version:
Sunday last week I caught someone looking to steal my bike (or just happened to be round a corner where the only thing of value is my bike and decide to run as though his life depended upon it when he saw me in my security guard uniform approach). My life savings are that bike so this worried me.
I brought a Blue fire alarm system from amazon, cheap as chips but highly rated by customers and amazons "recommended" product, sorry but the rules prohibit me from linking to it, but I am hopeful the actual specs matter little for this.
I installed it the next day by wrapping the red wire around the screw on the red terminal of the battery and the black wire around the ...well black part lol (all i was interested in is the alarm side and that was all that was needed to get it working).
The alarm worked a treat, however a few people had mentioned installing inline fuses to protect their bikes, so the next day I took it to a motorbike mechanic, he fitted an inline fuse and proper battery terminals. The alarm sounded quieter than before but i felt good knowing it was secure.
Fast forward to today, I go to turn off my alarm and its chirp sounded like the dieing throws of a powered down robot.....and it hit me...the thing was running off the backup 9v battery not bike battery. I took the battery out and hit the arm button, nothing, problem identified. I remembered the inline fuse holder had a spare fuse so I opened up the panel swapped the fuses and the alarm armed. put it back together, tested still armed. Then I turned my bike on (not the ignition but just the stage where the electrics come on and it does a self test, I just wanted to make sure the electrics of the bike were fine....they were but after that I could not set the alarm again) seems turning on the bike blows the inline fuse.

short
Turning on the bikes electrics blows the fuse to the alarm that was added....the bike is fine and functions perfectly but this fuse is an issue)

The question:
So here is where I am stuck, I am guessing that when the electrics are started there is a bit of a spike? The 20a fuse is fine with this but what ever fuse the bike guy gave me (The last two he had and he was in a rush) can not handle it, they are small glass fuses if that helps. (at work and its raining so I can not open up the bike to check, never seen glass fuses before though so guessing if its glass its a certain amp?)
would putting a 13amp house fuse work? (the sort you get in kettle plugs) or do i need to buy a 20amp fuse?
Since the bike works fine and the alarm functions ok on its backup battery is it safe to assume that the issue is purely the wrong fuse in the additional alarm side? (I am thinking that if there was a fault on the bike side I would of seen more of an issue with it and if it was the alarm side then the alarm would not of functioned for 3 days on a little 9v battery lol)

Any advice? fuses/electrical are not something I m familiar with, scary thing is most people just wire these directly to the battery, that cant be good right?

Thanks in advance and sorry for the wall of text, wanted to get as much info as i could over.
 

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Glass fuses come in many current ratings, from less than 1/10A to more than 20A. Do you have the manual for that alarm, and does it say what power or current is required?

What I think is happening is, the fuse is barely big enough to operate the alarm, and is a fast-blow type. When you turn the key on, the battery Voltage will drop abruptly, at least several tenths but maybe as much as several, because of the lamps. The alarm system probably has a large filter capacitor on the input, which is going to try to keep the Voltage from dropping, and push current back through the fuse, which is briefly high enough to blow a fast fuse. You will have to take the fuse out of its holder and read the numbers to get the value - they will be on only one end, and should show NNNV MMMA, for Voltage limit and Current rating. If you take it to an electronics parts store, or even some auto parts stores, you can get a replacement, but you need to know how much bigger you can safely go. If, for example, the manual says it draws 5A, you can use a 10A fast-blow or 7.5A slow-blow fuse, without any danger. In this situation, I would go with slow-blow (if you can find one), which will wait longer for the current to drop before failing.

Personally, while at the store, I would get an in-line holder for a modern fuse, and replace that glass filter. That way, you can keep a kit of replacements that fit all your fuses in your bike somewhere. Fuses do die from fatigue in normal use; not often, but always when you're miles from a replacement.
 

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Discussion Starter · #3 ·
Glass fuses come in many current ratings, from less than 1/10A to more than 20A. Do you have the manual for that alarm, and does it say what power or current is required?

What I think is happening is, the fuse is barely big enough to operate the alarm, and is a fast-blow type. When you turn the key on, the battery Voltage will drop abruptly, at least several tenths but maybe as much as several, because of the lamps. The alarm system probably has a large filter capacitor on the input, which is going to try to keep the Voltage from dropping, and push current back through the fuse, which is briefly high enough to blow a fast fuse. You will have to take the fuse out of its holder and read the numbers to get the value - they will be on only one end, and should show NNNV MMMA, for Voltage limit and Current rating. If you take it to an electronics parts store, or even some auto parts stores, you can get a replacement, but you need to know how much bigger you can safely go. If, for example, the manual says it draws 5A, you can use a 10A fast-blow or 7.5A slow-blow fuse, without any danger. In this situation, I would go with slow-blow (if you can find one), which will wait longer for the current to drop before failing.

Personally, while at the store, I would get an in-line holder for a modern fuse, and replace that glass filter. That way, you can keep a kit of replacements that fit all your fuses in your bike somewhere. Fuses do die from fatigue in normal use; not often, but always when you're miles from a replacement.
Ah that complicates things, if its not raining when i get home from work I will take a look at what is on the glass fuses (or tomorrow when awake as it will be 1am here). can I assume I can not replace a glass fuse with a standard home fuse?
The manual was little more than a hard to follow wiring guide, though for the main feature it was easy enough to follow. It was highly rated but very very cheap and clearly made on a budget. I would assume the draw would be very low though or it would of drained the little 9volt battery much faster than 3 days? but that is a pure guess.

The circuit I care about most is the bike one, thats the one I want to protect, since most people just attach the red wire and black wire direct to the battery I am assuming the alarm can take up to 20a (look on youtube for "bluefire motorcycle alarm" and there are tons of install vids not using fuses, though that seems crazy to me). The reason for this assumption is anything more than that would blow the main fuse to the fuse box so wired directly in it has to able to take that max or people would be moaning about fried electricals.......but i could be wrong there.....this is all new to me.

Some point next week I have a package arriving from Maplins with crimps, electrical connectors, tools etc so I would have the tools to do what the mechanic charged for, when I ordered them it all looked so simple lol. I will likely replace the glass one with a modern one (when i figure out what a modern one is lol) then, the glass fuses and inline holder were about £3 each so getting a glass one to tie me over until the package arrives will not break the bank assuming the modern ones are as cheap?
 

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For a modern type fuse, just look at any of those in your bike; they are probably little plastic rectangles, with two metal blades sticking out one side.

As far as current draw goes, you noticed it was quieter when running on the 9V battery, so I suspect it will draw more than the battery can provide when sounding the alarm. I'll search for that alarm, to see if I can find a proper fuse size for you.

UPDATE: unfortunately, no one has measured the current draw when the alarm is sounding, just the standby current when the 9V battery is removed or dead. When you find the rating for the fuse you have, please post it. I see that the unit connects to the ignition path, so that may be where the current surge is going.
 

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Discussion Starter · #5 ·
For a modern type fuse, just look at any of those in your bike; they are probably little plastic rectangles, with two metal blades sticking out one side.

As far as current draw goes, you noticed it was quieter when running on the 9V battery, so I suspect it will draw more than the battery can provide when sounding the alarm. I'll search for that alarm, to see if I can find a proper fuse size for you.
That is greatly appreciated, its listed on amazons uk site as "BlueFire 12V Universal Motorcycle Alarm System Anti-theft Security Remote Control Engine Start for Motorbike Scooter" but i know 12volt is not the same as 12amps :(. Someone on their QnA said they fitted a 5a fuse but then their bike may not be as electrical as mine (which I assume makes a difference, the whole display is lcd and when you turn the electricals on there is a small whiring like a motor, maybe the coolant pump.....I wish i knew more about these things, i feel clueless)
 

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All of the inline fuses of the glass type have failed for me at some point.
The U shaped type found in cages are better, and better still are the ones used in boats. Your local marine supply store should have them. Blue Sea is a good brand.

UK
 

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Discussion Starter · #8 ·
While searching, I did find this: **url removed, else it will not let me post my reply lol**
Did you connect all the wires, or just the red and black wires?
@;

Just the red and black, I had planned to add the blinkers later but doesnt seem too needed. Remote start, I have no idea who would have a need for that lol. It was just the alarm I was after too and wanted to limit the amount of cables i needed to mess with. Should I of wired up another part? would be typical if I messed it up while trying to be as non invasive as possible lol

The linked alarm does seem very close to the one I have (no cutting of cable was needed and the symbols are different for silencing the alarm but I am willing to bet the innards will be essentially the same, the rest of the wires certainly look right)
 

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OK, just red/black - is there any chance any of the other wires could touch a ground? IOW, did you tape them, so that they can't?
 

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Discussion Starter · #11 ·
OK, just red/black - is there any chance any of the other wires could touch a ground? IOW, did you tape them, so that they can't?
The glass fuses were 10a and 20a
But I think they were duds, I put a household 3a fuse (the red kind) and it is working fully now. Should hold until I can get the proper bladed kind (I assume the 3a fuse won't be an issue even though its not a glass one? Man I wish I could link to things! )
The wires needed to be trimmed down to use (rubber covers them fully) so I did not tape them, but then it's mostly plastic in there and they are cable tied to prevent movement.

Right I need sleep, hopefully that 3a fuse will be OK for now (if you go to the screwfix website, a UK electrical and DIY store and search for 94488 it should show a pack of 10 of them, its one of them I have installed for now)
 

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Is it at all possible that what you had was a 1a and 2a? That might explain why the 3a is working. I just don't see how a 3a would not blow replacing a 20a unless possibly you replaced a fast blow with a slow blow but that's still a stretch.
 

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Glass fuses are vulnerable to vibration, and twisting the ends, because the seal between the glass tube and metal ends is often poor. Sometimes, the wire connection to the ends just isn't good to begin with. Regardless of current rating, I've had new ones fail in minutes, without visibly burning the element inside, and only verified with a meter. I, for one, was glad to see them fall out of favor, for the newer, and IMO better, designs.
 

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Discussion Starter · #15 ·
Is it at all possible that what you had was a 1a and 2a? That might explain why the 3a is working. I just don't see how a 3a would not blow replacing a 20a unless possibly you replaced a fast blow with a slow blow but that's still a stretch.
One had 20a on it the other 10a but they may of been faulty, I will explain why I think that further down as it relates to what the other chap said

It could also be whatever was shorting the fuse is no longer shorting the fuse.
Hope that's not the case as that would mean it could fail me at random


Glass fuses are vulnerable to vibration, and twisting the ends, because the seal between the glass tube and metal ends is often poor. Sometimes, the wire connection to the ends just isn't good to begin with. Regardless of current rating, I've had new ones fail in minutes, without visibly burning the element inside, and only verified with a meter. I, for one, was glad to see them fall out of favor, for the newer, and IMO better, designs.
Is the metal inside the fuse supposed to be visably damaged? Reason I ask is on both of them the metal inside looked intact however on the 10a the metal cap fell off when I removed it
 

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Glass fuses do bad a lot. I had a 1970's D100 (Dodge pick up) and I remember many of the fuses melting the fuse block and them falling apart, and no the metal and glass part is supposed to be firmly intact.
 

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The metal visible in the glass is what melts when the fuse blows, and usually at or near the center. The end caps shouldn't come off, ever.
 

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When you add someting to the bike ALWAYS add a fuse for it.
RTFM to find the right size fuse.

In your case, I see you talking about 13 amp fuses for an alarm.
You shouldnt need that much.
I would expect an alarm to be 5.

So, if the alarm SHOULD use 5 but you are blowing a 5, then something is wrong, obviously.
What to do ?

Measure resistance from the alarm end of the fuse to ground.
Divide 13 by this resistance in ohms.
This is what the amp draw is.

Why did I say 13?
A 12v motorcycle battery in good shape is actually a bit over 13vdc.
In fact its is electrically dead at 12. Any time spent below 12.5 is permanent damage to a lead acid battery.

You might have a bad alarm or you might have a short somewhere.
I hope this both gets you started troubleshooting and serves to help others in their troubleshooting.
 
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