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Fuse sizes

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robert_ellison

Jedi Trainee
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Now I'm confused. Are all american fuses double the capacity of english fuses. Are the values I have received in other posts:
generator 2-3 amp
panel 2.2 wt
headlights 15 amp
overdrive 7.5 amp
taillights 5 amp
license plate light light 2 amp
fuel pump 7.5 amp slow blow
wiper motor 20 amp slow blow
supposed to be 1.2 half the size fuse as indicated or what?

Also, what about if I use a 10 amp slow blow in the fuel pump instead of a 7.5 amp fuse. Will I be defeating the purpose of fusing the circuit?
 
Those listed above are the required US fuse sizes based upon the type of load and its current characteristics. Because the fuel pump is unique no two may not be exactly alike from the current stand point, so you can use use a 7.5 Amp fuse initially and if it blows then increase it to 10. if does notleave it alone.

No British fuse VS US rating ratios are not 2-to-1 how ever as a grassroots choice you will be fairly close.---Fwiw--Keoke
 
Robert, I'm with you. Too many things have been said unclearly. And how are the different fuses marked to let you know what you've got? Some say Buss and some say other things. I have a 30 amp on my headlights that I believe is a 15 amp but who knows till it blows. Some have paper inside with the amps written on them but are they British or US.
 
I have what I believe is the original 50 amp fuse in my fuse block and it is engraved with the initials UK meaning it is a British spec fuse. The Buss fuses I believe are U.S. spec fuses. I am using a 20 amp Buss (U.S. spec) fuse in the A3/A4 fuse holder which originally had a 35 amp UK fuse. I have added in-line mini blade-type fuses which are U.S. spec for my overdrive solenoid (10 amp) and my rear lights (5 amp).

By the way, the wiper is already fused with the A3/A4 fuse as is the heater blower and horns and anything else fed with a green wire. The fuel pump is not fused nor are the light circuits except for the turn signals (powered by the flasher which is fused) (All this applies to BN4/BN6/BN7/BT7)
 
I might have confused you with this post:

<div class="ubbcode-block"><div class="ubbcode-header">Quote:]While you are at it, I would check to see if your fuses are british spec or american. If you have replaced the standard fitted Healey 35a or 50a with a local sourced from walmart (or wherever you americans buy fuses from) its asking for trouble.
Original lucas fuses that are rated at 35a (will be rated 17a continuous and 35a trip / blow. Therefore if you have replaced it with an american fuse that says 35a made by bussmann (or whoever, they will be marked AGC as a standard for US) it is rated at 35a continuous and 60a blow. Much more than the prince of darkness intended. Hence frazzaled loom letting out smoke.

Just make sure the standard 2 healey fuses are either 50a british / 25a US and 35a british / 20a US.
ps British fuses tend to be marked IEC.[/QUOTE]

Basically what I was trying to highlight is if you only have the original 2 fuses in your healey you should make sure they are 25a and 35a (US Spec), so they will provide a 'little' protection. If you or a po had replaced them previously for american spec fuses marked up with the same rating they would provide no protection.

Just use your american fuses and dont mix the two types up. To work out their sizes, basically add up the wattages in the circuit and divide by 12 volts, ie 4 x 5watt lights = 20w / 12 volts = 1.67 amps so go for a 3a or 5a fuse (US spec).

British fuses are slightly shorter at 30mm and will usually be marked IEC, american fuses are 32mm (1.1/4") and will usually be marked AGC.

So just buy your american fuses and spec, and just replace the 2 original fuses for the sizes outlines above.

hope I have not confused you more?
cheers Andy
 
tahoe healey said:
Robert, I'm with you. Too many things have been said unclearly. And how are the different fuses marked to let you know what you've got? Some say Buss and some say other things. I have a 30 amp on my headlights that I believe is a 15 amp but who knows till it blows. Some have paper inside with the amps written on them but are they British or US.
Click to expand...

WE Can not teach electricity 101 on the forum we simply try to provide you with guidance where possible based upon our back ground and experience. If you do not care to use just disregard it and do it uour way.--Regards--Keoke


GOOD SHOW ANDYBJ8
 
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After all the discussion on additional fusing, I have installed a new fuse box with 8 fuses to get individual fusing on all the switched circuits including the overdrive and the fuel pump. Yes it is in crooked, but I had to cut a corner off to fit. Everything works.
 
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