melted fuse (not blown) - Triumph Forum: Triumph Rat Motorcycle Forums
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post #1 of 19 (permalink) Old 05-20-2019, 03:20 PM Thread Starter
wol
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melted fuse (not blown)

I have a 4 way fuse block on my T140 hooligan bike - fuses are the "standard " size two prong things as fitted to those 4 wheel cars -- had a sudden loss of volts so checked the fuses - these fuses have a colour coded plastic back to them - i use one as a main fuse from which the other 3 fuses are fed - i found that on the main fuse the plastic part had melted into the plastic of the fuse box and had finally blown (it looks like it had been melting for a while before it finally blew or could have just fallen apart )- there was another fuse that had begun to melt but was still OK - main fuse was 25 amp and the other i think 10 amp --- it it suggests to me that the fuses were getting hot enough to melt the plastic part but not blowing ---- could it be a just a bunch of cheap plastic used to make the fuses - could it be loose wires ( connctors to the fuse box are those nasty crimp on spades) -- there is no evidence that the wires to or from the fuse bos have been hot -- wires are new thin wall type big enough for the job but not massively oversize

anyone got a suggestion as to cause ( std wattage headlamp - rear is an LED - so no power load bigger than standard )

got a replacement fuse box on it way so will rewire and give it a good looking at
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post #2 of 19 (permalink) Old 05-20-2019, 03:55 PM Thread Starter
wol
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just done an information exchange with Mr Google -- likely / possible cause is a poor connection - will change the nasty connectors to better crimped ones and see how it goes
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post #3 of 19 (permalink) Old 05-20-2019, 04:59 PM
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Unless it's a slow blow fuse 25A is too big
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post #4 of 19 (permalink) Old 05-20-2019, 06:25 PM Thread Starter
wol
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yes 25 is too big -- but all circuits are protected by lower sub fuses -
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post #5 of 19 (permalink) Old 05-20-2019, 11:39 PM
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Hi Wol
Original main (single) fuse was 35amp.
Perhaps it is build up of heat over a period of time in the 25 amp fuse.
Regards
Peg.
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post #6 of 19 (permalink) Old 05-21-2019, 03:01 AM Thread Starter
wol
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I will change the main to a 15 amp and see how it goes ( and keep a selection of spares in my pocket)
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post #7 of 19 (permalink) Old 05-21-2019, 03:45 AM
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Hi,

Quote:
Originally Posted by Rancidpegwoman View Post
build up of heat over a period of time in the 25 amp fuse.


Quote:
Originally Posted by wol View Post
fuses are the "standard " size two prong things as fitted to those 4 wheel cars
main fuse was 25 amp
Quote:
Originally Posted by Rancidpegwoman View Post
Original main (single) fuse was 35amp.
Misunderstanding fuse ratings ...

. Wol's "'standard' size two prong things as fitted to those 4 wheel cars" are rated 'continuous' - i.e. a "25"-marked fuse can conduct up to 50A without blowing, because "blow" is double 'continuous'.

. "Original main/single fuse" - fusible strip attached to a metal cap at each end of a glass tube enclosing the strip - ONLY in GB were the numbers on these a 'blow' rating which, as I say, is double 'continuous' - many of these fuses used to have a small piece of paper inside the tube with both 'blow' and 'continuous' ratings; e.g.:-

35 Amps blow
17.5 Amps continuous

. In GB, you have to be careful with glass-tube-metal-ends fuses. The rest of the world rates all fuses 'continuous', the Japanese use that system so a Japanese glass-tube-metal-ends fuse marked "35" is 35 Amps continuous, 70 Amps 'blow'.

Quote:
Originally Posted by wol View Post
25 is too big -- but all circuits are protected by lower sub fuses
Nope:-

Quote:
Originally Posted by wol View Post
4 way fuse block
one as a main fuse from which the other 3 fuses are fed
... so only three other circuits can be protected by the "lower sub fuses".

The "main fuse" is supposed to protect against the unforeseen; as I say, the "25" (Amp) "'standard' size two prong things as fitted to those 4 wheel cars" actually could conduct up to 50 Amps without blowing - is the bike's wiring 4.5 sq.mm. or larger conductor? if not, the unforeseen could melt wires before the fuse blows ...

"main fuse from which the other 3 fuses are fed" means the fuses are all on the same 'side' - positive or negative - of the electrics. On a bike without an electric starter, the 'main' fuse should be in the single wire attached to the battery 'earth'/'ground' terminal, +ve or -ve, to protect against short-circuits between the other battery terminal and any other part of the bike (which, by definition, is connected to the battery 'earth'/'ground' terminal). Fuses protecting individual circuits then should be in wires connected to the battery 'non-earth/-ground' terminal.

Hth.

Regards,

Stuart
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post #8 of 19 (permalink) Old 05-21-2019, 03:54 AM Thread Starter
wol
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Thanks stuart - need to re-read that a few times but its begining to sink into my ageing grey matter -- time to rewire all my fuses methinks
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post #9 of 19 (permalink) Old 05-21-2019, 04:43 AM
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Quote:
Originally Posted by wol View Post
just done an information exchange with Mr Google -- likely / possible cause is a poor connection - will change the nasty connectors to better crimped ones and see how it goes
I like to solder as many connections as possible for that same reason. Hi current going through a high resistance connection gets a lot of power dissipated as heat. Very common in headlight connectors

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post #10 of 19 (permalink) Old 05-21-2019, 09:11 AM
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Iíve read that crimped connections are actually better than soldered connections on motorcycles because of the vibration. Apparently vibration can crack soldered connections and cause a poor connection. I donít know if this is true, but I now crimp all mine.
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