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Should A 30 A Fuse Blow Almost Immediately After Fitting

electrical

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#16 68+86auto

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Posted 11 December 2023 - 02:05 AM

A modern 30A fuse is NOT suitable and is a good way to melt wiring.

The short version is that the Lucas fuses originally fitted were rated differently and a 15A modern fuse is a closer equivalent. To confirm you can compare the internal fuse wire/metal size of an original Lucas vs modern fuse. If you look at a 30a modern fuse the fuse material is very obviously a larger diameter and therefore takes a lot higher current before blowing (very bad idea).

If you want more information there are plenty of discussions online about it.

 

Fit a 15A fuse.

 

 

The fuse is blowing because you have a fault. I am currently rewiring a vehicle because someone had decided to add an electric fan as well as indicators using the original trafficator supply wiring. They obviously had fuses blowing so what did they do? Bypass the fuse. The result was of course melted wiring and a melted terminal block. Increasing the fuse capacity like you have done would've ended with a similar result.


Edited by 68+86auto, 11 December 2023 - 02:12 AM.


#17 mad4classics

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Posted 11 December 2023 - 08:56 AM

Once you've tracked down the fault, Durite make fuses to the original 17a/35a rating part number 0-374-35.
Available from Green Spark Plug Co. for instance.

https://www.gsparkpl...0-0-374-35.html

(0-374-25 is the 12/25 & 0-374-15 the 8/15)

EDIT: although still in stock with various suppliers these too are now discontinued.

Edited by mad4classics, 12 December 2023 - 08:29 AM.


#18 cal844

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Posted 11 December 2023 - 09:49 PM

What you need is a 17 amp continuous glass fuse, or 35 amp blow rating, which is how glass fuses are rated.

I get mine in a kit from Halfords or my local parts stores

Edited by cal844, 11 December 2023 - 09:50 PM.


#19 Vinay-RS

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Posted 12 December 2023 - 05:16 PM

A modern 30A fuse is NOT suitable and is a good way to melt wiring.

The short version is that the Lucas fuses originally fitted were rated differently and a 15A modern fuse is a closer equivalent. To confirm you can compare the internal fuse wire/metal size of an original Lucas vs modern fuse. If you look at a 30a modern fuse the fuse material is very obviously a larger diameter and therefore takes a lot higher current before blowing (very bad idea).

If you want more information there are plenty of discussions online about it.

 

Fit a 15A fuse.

 

 

The fuse is blowing because you have a fault. I am currently rewiring a vehicle because someone had decided to add an electric fan as well as indicators using the original trafficator supply wiring. They obviously had fuses blowing so what did they do? Bypass the fuse. The result was of course melted wiring and a melted terminal block. Increasing the fuse capacity like you have done would've ended with a similar result.

 

Thank you so much! This is really helpful and essential. Would rather not have a fire starting in the engine. 

 

Once you've tracked down the fault, Durite make fuses to the original 17a/35a rating part number 0-374-35.
Available from Green Spark Plug Co. for instance.

https://www.gsparkpl...0-0-374-35.html

(0-374-25 is the 12/25 & 0-374-15 the 8/15)

EDIT: although still in stock with various suppliers these too are now discontinued.

 

Thank you! I will check if I can find a local supplier who stocks those fuses. 

 

What you need is a 17 amp continuous glass fuse, or 35 amp blow rating, which is how glass fuses are rated.

I get mine in a kit from Halfords or my local parts stores

 

Awesome. I will check locally if I can find those fuses here. 



#20 Steam

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Posted 13 December 2023 - 05:02 AM

A standard 20A glass auto fuse will do the job.

#21 68+86auto

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Posted 17 December 2023 - 07:05 AM

A modern 30A fuse is NOT suitable and is a good way to melt wiring.

The short version is that the Lucas fuses originally fitted were rated differently and a 15A modern fuse is a closer equivalent. To confirm you can compare the internal fuse wire/metal size of an original Lucas vs modern fuse. If you look at a 30a modern fuse the fuse material is very obviously a larger diameter and therefore takes a lot higher current before blowing (very bad idea).

If you want more information there are plenty of discussions online about it.
 
Fit a 15A fuse.
 


Here on the left is a "35A" fuse I just removed from a vehicle compared to an old genuine Lucas 35a one on the right. The fuse wire is visually smaller on the correct one. The incorrect fuse is also too long.

Attached File  20231217_165841~2.jpg   53.14K   0 downloads

#22 nicklouse

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Posted 17 December 2023 - 09:19 AM

Never seen a fuse like the one on the right.

 

local production?



#23 68+86auto

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Posted 17 December 2023 - 11:44 AM

Never seen a fuse like the one on the right.

 

local production?

 

It is actually out of a 1951 vehicle (a Jowett so UK made). I haven't seen a mini with ones like it but the fuses have the same ratings and size.







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