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The wonderful world of Lucas [fuse question]

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beebopbogo

beebopbogo

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I'm an american living in a world of american parts and ratings. My B was of course born in England with English parts and ratings. Could someone tell me how the British fuse ratings compare to American fuse ratings?

My 4-way fuse box should be full of "17 amp current rated, 35 amp blow rated" fuses according to the Haynes manual. American fuses come in 10, 15, 20, and 30 amps. Should I use the rating closest to 17? Or 35? Also, should I go too high or too low when matching up the fuses. For instance, matching a 17 amp, should I use the 15 or the 20?

--Beebop

P.S. I ran the 'B around the block for the first time after putting the new cylinder head in and it ran great! I'm just nervous about overheating, and since the guages don't work at the moment, I figure I'd better fix that before cracking my head (either the car's or my own).
 
Aloha Beebop,

Typical glass tube auto electrical fuse type 3AG/AGC in the United States and are UL rated. A 15 Amp fuse is UL tested at 110%, 135% and 200% overload and the time at that load to "blow". For 15 amp fuse, the time standard is 4 Hours, 1 Hour and 10 Seconds respectively at the overload schedule above. In your case I would use a 15 Amp fuse as most closely matching the original required protection. The Lucas requirement which I would interpret to mean 17 amp normal working load, 35 amp "blow" load. You can always use a lower rated fuse for added protection, particularly if you are concerned about the integrity of the circuit. Fuses are a lot less expensive than a wiring harness and much easier to replace.

Congratulations on the head replacement.

Safety Fast,
Dave
 
I played this game myself and found that the 15 holds in most instances, however, sometimes running more and having poor connections over time, you may need 20's. I finally answered it by buying a whole new box with "BRITISH" fuses (Lord Lucas's own) and extra fuses from B Hive. You are still under $30 bucks and considering the damage that can happen to "vital" parts that cost a lot more, it was well worth the investment. Check and change all the connectors on the fuse box while you are at it. /ubbthreads/images/graemlins/yesnod.gif
 
Mr. Bee, When you take out the fuses, wiggle the holders on each end and make sure there's no movement. They're just riveted to the buss bar on the back of the fuse box and come lose over time. Then they arc and/or corrode yielding weak connections at the box, I think they must be meant for replacement every 20 years or so. Also if all your guages are out, check the voltage stabilizer and/or its connections, it's mounted under the dash on the back of the firewall near the hood-release cable.
Lots of luck,
Tim Matheis
 
One more thought. The prior owner tapped under fuse number three for the radio on mine and that "tap" shorted taking out the guages. Check for "homemade" wacko taps. The wire would look out of place coming through the firewall plug and tapping into fuse 3 on the back. The insulation behind the fuse box is just a piece of "pleather" and lousy.
 
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