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35 amp fuses

Posted by Lightfoot 
Lightfoot Avatar
Ralph Bell
Martinez, California, USA   usa
1979 MG MGB

I'm confused. I've been looking for slo-blo ceramic 35 amp fuses in all of the local automotive stores, and no one has had any in stock. I read something recently that indicated we could replace our original fuses with a lower amperage modern type of fuse. What do I look for when I go to buy a replacement? Do I just buy one of the generic glass types rated at 20 amps? My car is a 79B. Thanks.

PS. I did read Mac's post below, but I'm not sure what AGC means.

you want AGC 15 or 20. The top two would work fine wioth less because they control just the side lights/parking lights. I have found theat the bottom two need 20...they too readily blow 15s.

the original fitment was a 35 amp Lucas but the threshold on these fuses (the point at which it blows) is far sooner than what an AGC 35 fuse would be...the correspondnace is about 2x. so a 17-1/2 would be equivalent but you can't find them so 15 or 20.




Edited 1 time(s). Last edit at 02/14/2008 09:21PM by Lightfoot.
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cfrench Avatar
Carl W. French
alfred, Maine, USA   usa

15-20, 18 is the match but some people are running 15 on the top two and 20 on the lower two slots.



Carl W. French
Alfred, Maine
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67B will be in our will
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Swamperca Avatar
Swamper CA
-, Nor Cal, USA   usa
1968 MG MGC GT
1968 MG MGC GT "California Chrome"
1969 MG MGB GT "Rat"
1969 MG MGC GT "C-Rod"
1970 MG MGB GT "Widow"   → more

Go to Radio Shack.



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The Wiz Avatar
Mike The Wiz Barnes
STL, MO, USA   usa
1969 MG MGB GT
1971 MG MGB GT "Blueberry"
1979 MG MGB "PopTop"
2000 Ford Ranger SC4x4
2001 Mercedes-Benz SLK 230 Kompressor

If you have a Jaguar dealership near you they carry the correct fuses.





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1971 MGBGT, overdrive, Limey relay and fuse kits, Rick Ingram struts all round, Jeff Schlemmer points distributor, mgccars.com alternator, Basil Adams camshaft and side cover, Eurospec tail lights, 1976 dashboard and console, 1999 Chevy cavalier seats, GM heater motor and fan with Ford 3 speed controller, Ford Merkur/Sierra parcel shelf, cruise control.

1979 B, Olds 215 engine with 1996 Landrover heads, Carter AFB, Camaro T5 gearbox, Limey relay kit, Rick Ingram struts all round, mgccars alternator, Jeff Schlemmer distributor with Petronix, Eurospec tail lights, cruise control, 99 Pontiac Sunfire seats.

1969 MGBGT, Miata seats, late centre console, apart from that it's stock!
Hurst Nuckols
Midway, Ky, USA   usa

You can replace the fuse block with a modern one fairly inexpensively. I saw them at Advance the other day when I was buying a new inline fuse thing for the headlights. Check it out next time you are in there, they are right around the fuses. Also, you could replace the fuses with circuit breakers for the higher amp stuff too, just another idea. You won't hurt anything if you go slightly lower amps (30 amp I think is pretty readily available in the buss glass fuses if that is what you have in your B like I do in my 71), but you may blow the fuse. I am not sure about the replacing with a lower amp modern one. Fuse ratings are fuse ratings I think...

Hurst
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ingoldsb Avatar
Terry Ingoldsby
Calgary, Alberta, Canada   can
1971 MG MGB

There is really no reason not to use standard AGC20 fuses. The originals were essentially identical - they just used a different method of rating. So a factory 35 Amp fuse is very close to the American standard AGC fuse.

AGC refers to the style (length, size, shape) of the fuse. You will find all sorts of letters like SFE, AGC, etc. AGC was (and is) very common.



Terry Ingoldsby
terry.ingoldsby@DCExperts.com
Lightfoot Avatar
Ralph Bell
Martinez, California, USA   usa
1979 MG MGB

Thanks for the replies. I understand now that our newer fuses, at 20 amps closely approximate the original 35 amp lucas fuses. I would like to install a newer fuse block. Ray Wyberski did a great job with this, but I would not try it without some good instructions.
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RSS Avatar
RSS Gold Member
R SS
Virginia, USA   usa

Lightfoot Wrote:
Quote: Thanks for the replies. I understand now that our newer fuses, at 20 amps closely approximate the original 35 amp lucas fuses. I would like to install a newer fuse block. Ray Wyberski did a great job with this, but I would not try it without some good instructions.

Instructions? Uh-oh..... :eyepop:







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Tom Bedenbaugh Avatar
Memphis,Tn, USA   usa

In the 20+ years I have been working on British cars I have always replaced a blown fuse with a regular old 35 amp fuse and never had a problem with that practice.

Just today I had to replace a new out of the box brake light switch(I installed yesterday) that was blowing 35 amp fuses. After blowing two fuses and looking for a dead short in the wiring I decided some how the switch itself was grounding internally. The switched circuit has a lot of stuff pulling current.



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Lightfoot Avatar
Ralph Bell
Martinez, California, USA   usa
1979 MG MGB

Buy Tom, Which type of fuse?
mac townsend Avatar
Fairfield, CA, USA   usa

any auto parts store will have AGC 15/20

i do not know what the acronymn means, and don't care.

no need to get fancy/ radio snack is costly for this kind of stuff. A buck fifty for a box at Kragens.






1973 Pale Primrose Roadster. A nice 10-footer!
SUs, Datsun 5-speed
MGB Tips and Tricks: www.mgrescue.com
mac townsend Avatar
Fairfield, CA, USA   usa

Tom Bedenbaugh Wrote:
Quote: In the 20+ years I have been working on British cars I have always replaced a blown fuse with a regular old 35 amp fuse and never had a problem with that practice.
Just today I had to replace a new out of the box brake light switch(I installed yesterday) that was blowing 35 amp fuses. After blowing two fuses and looking for a dead short in the wiring I decided some how the switch itself was grounding internally. The switched circuit has a lot of stuff pulling current.

what's a "regular old 35 amp fuse"?

AGC 35 would be about the same as using foil as it would permit current well beyond that -- about double). if there were no problems, that is because you solved them before using the fuse<G>



1973 Pale Primrose Roadster. A nice 10-footer!
SUs, Datsun 5-speed
MGB Tips and Tricks: www.mgrescue.com
Swamperca Avatar
Swamper CA
-, Nor Cal, USA   usa
1968 MG MGC GT
1968 MG MGC GT "California Chrome"
1969 MG MGB GT "Rat"
1969 MG MGC GT "C-Rod"
1970 MG MGB GT "Widow"   → more

Maybe he means the old original type slow blow fuse which I've found at my Napa and Radio Shack.
Tom Bedenbaugh Avatar
Memphis,Tn, USA   usa

nope AGC 35, you can buy them at any parts store. Like I said that's all I have used in all British cars for 20+ years and never had the smoke get out. I have replaced hundreds of them.



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jdeluke137 Avatar
John English
Jefferson, Georgia, USA   usa
1976 MG MGB

At Atlanta Imported, they have a fuse - AFB-135 - that they describe as "17 amp hold, 35 amp blow", which I believe is actually what the original fuses were. It's Moss part number 146-700. Here's the link to the Atlanta Imported site, where you can see a picture. Search on "fuse", and then look at the 5th line item - click on the picture to blow it up.

www.atlantaimported.com



John English
1976 MGB
HIF44 carb on late manifold, Schlemmerized 45D w/Pertronix, Limey's relay kit, solid state voltage stabilizer.


Luke 1:37
Benny Avatar
Ben E
San Diego, CA, USA   usa

Ok, pardon my ignorance, but if I grabbed a 30 Amp glass fuse from Pep Boys (not AGC or anything, just 30 Amp), is that too much fuse?

Am I reading this corrctly that modern fuse ratings are different than old ones?
sultanoswing Avatar
Curtis _
Hamilton, New Zealand   nzl
1971 MG MGB GT "The 'Gee"

FWIW I replaced my original, worn fuse block with a modern, 4-fuse blade fuse block. Easy, cheap, and the 20 Amp blades work excellently well - they have blown appropriately, and never not.


Kimberly Avatar
Kimberly ?
Pinole, CA, USA   usa

Benny Wrote:
Quote: Ok, pardon my ignorance, but if I grabbed a 30 Amp glass fuse from Pep Boys (not AGC or anything, just 30 Amp), is that too much fuse?
Am I reading this corrctly that modern fuse ratings are different than old ones?

The letters (AGC,etc.) refer to how the fuse is rated and its physical size. There is no such thing as "just a 30amp fuse".
If you use AGC fuses, then you will want to use 15 or 20 amp. Depending on how the fuse is rated, 30 amp may not offer the protection the wiring in your car should have. Be aware that AGC fuses may not fit the original inline fuse holders. They will work without a problem in the fuse box.

I find no advantage to changing the fuse box for one that takes blade fuses except if the original fuse box is corroded. It is the rating of the fuse, not the style of the fuse that protects the wiring.
Wray Avatar
Wray Lemke
., South Carolina, USA   usa

Easy for me to weigh in; I just wait until Kimberly puts it plainly and say "Das right".

I also see no advantage to replacing the fuse block with the ATO style, you have to take into account the jumpered configuration of the OE block to do it correctly.



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Pat Neher
Alexandria, VA and HuffS Church, PA, USA   usa

I'm not disagreeing with anyone's experiences, just want to post that Rick Astley notes in his book that a 15 amp AGC is the closest in characteristics to the oem 17/35 fuse.
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