MGB help! fuse replacement 77 MGB

[Edward]

help! fuse replacement 77 MGB

I have blown a couple of fuses while doing some rewiring. 4 blocks on my panel, 17amp continous/35amp blow rating. Is there any standard type glass fuse that I can replace with. All the auto parts shops in the area do not carry british type. Need advice on amps and replacement, want to do some driving this weekend!!!!!Thanks!! /ubbthreads/images/graemlins/driving.gif

 

[Geo Hahn]

Re: help! fuse replacement 77 MGB

Get a 20 amp American glass cartridge fuse (e.g. Buss). This is roughly equivalent to a Lucas 35 amp fuse.

 

[fadler1]

Re: help! fuse replacement 77 MGB

I found the exact fuses in boxes of five (never enough of them) at Kragen Auto Parts, west coast

 

[SilentUnicorn]

Re: help! fuse replacement 77 MGB

[ QUOTE ]
Get a 20 amp American glass cartridge fuse (e.g. Buss). This is roughly equivalent to a Lucas 35 amp fuse.

[/ QUOTE ]


i dont know if your kidding or not...lol



mark /ubbthreads/images/graemlins/driving.gif

 

[Dave Russell]

Re: help! fuse replacement 77 MGB

George is right on & not joking.
A fuse requires heat (power, watts) to melt the element. The heat applied to a fuse element follows the formula of I squared R (amps times amps times the fuse resistance). Since the fuse resistance is approximately constant it boils down to the speed of melting is proportional to amps times amps.

The 17/35 amp English rating says that the fuse will carry 17 amps continuously & eventually melt at 35 amps. If for example the 17/35 fuse would melt in one minute at 35 amps, with 70 amps applied it would have four times the heat applied & melt in 15 seconds. With 140 amps applied it would have 16 times the heat & melt in 3.75 seconds. All simple fuses roughly follow this rule.

The USA rating system gives the current required for the fuse to eventually melt, not continuously carry. Thus a 20 amp USA rated fuse with 35 amps applied will melt in about the same amount of time as the 17/35 English rated fuse.

The above melt times are for example only & the actual times may be different.
D

 

[JTB]

Re: help! fuse replacement 77 MGB

Thanks for that explanation. I have a bunch of Buss fuses and am running some that are lower apparent rating than the 17/35 spec'd. I was running some much lower ones (5 amps) while I tested my new wiring harness but kicked them up to 20 after I was done.