308 Fuse Block Conversion, Part Two: The New Fuses

For #3, the fuse voltage rating is a "maximum-do-not-exceed" value so no worries using them at 12V.

Your power calculations are not applicable -- the voltage drop across the fuse at full current is not the full 250V (more like a few tenths of a volt regardless of the max voltage rating).

 

Dave,

I will let a more qualified person respond to the question on fuses. However as someone who has repaired my fuse blocks I can tell you it is much simpler, and less expensive to repair your existing fuseblock than it is to replace them. What happens is that the rivets that hold the buss bars together work themselves loose over time. You could tighten the rivets but that would only be a temporary fix. A permanent fix is to flow solder from the rivet to the buss bars. This makes a secure connection and resolves the fuse block issue. It also retains your original fuseblocks. Having an aftermarket fuseblock would be a less desireable fix IMO.

 

Soldering the fuseblock addresses only one of the two large issues with the OEM block (the rivet design). It does not address the fact that the fuse holders themselves are a bad design, and grip the fuses by only a tiny contact area which easily corrodes. As long as you clean these occasionally and solder the rivets you can keep an OEM fuseblock working fine. But it is still something you will need to deal with frequently because they don't take long to get flaky again. Replacing it with something better means never again having to deal with it. Some people have been lucky with the OEM fuseblocks and never have trouble with them. Others are not so lucky.

As for fuses, the ones in the Radio Shack catalog are typically for home electronics use. If you go to an auto parts place, they will have automotive fuses rated at 12 V if that makes you feel better.

 

I'm going to have to strongly disagree here for a number of reasons:

1. Making a new pair of fuse boxes should take less than an hour and cost about $40 in parts.

2. Installation of 'home made' fuse blocks takes less than 10 minutes and uses all of the factory mounting points. IE easily reversible.

3. The made fuse blocks have less resistance than the OEM ones ensuring that EVERYTHING electrical will work better for you. To expand on Birdmans post, they never need any service to the fuse contact points the way the OEM ones do (even if they are soldered)

4. I'm an originality freak but the benefits of the aftermarket boxes are just too great. I still have my originals and can swap them out in 10 minutes should I feel like 'going original'. Not only that the fuse boxes are totally invisible unless you start removing panels. It's not like you are staring at Autometer guages or anything like that.

 

I have to agree with Novulari.
I am still running stock fuse blocks and I don't have any problems with them but during my sound system installation I checked voltage across the fuses and there was a marked drop. Not enough to pose a problem but with a "glass" fuse set up the voltage drop is near zero, almost always.

 

I have to agree. Mine have been working fine for 2 years now with no more problems.
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Dave,
I used to work for one of the big 2 fuse companies. Let me maybe shed some light on it without getting too techie.

1. Glass tube fuse designations indicate physical size (1/4", 5mm, etc. and also length) and performance (fast or time delay).

2. I do not have a catalog in front of me but I would recomend a fast blow for all applications. Both versions are rugged enough.

3. Do not confuse voltage with current in a fuse application. The voltage rating is there to establish a never exceed V to prevent arcing after a "blow" by either the parted failed short circuit strip (element) or by trace carbon on the glass. To a fuse, current is current is current - regardless, up to the never exceed voltage. In other words, 2, 12, or 110v.

4. NEVER exceed the recommended spec fuses. I would be willing to bet that you will never have any problems going even several amps under due to the lower resistance of the new fuse holders. If car vibration ever caused a fuse to blow, I guarantee it was at 99.9% of stated rating anyway.

One thing to remember guys is that barring a direct short, these fuses do not blow imediately when they encounter their rating (even the fast blow). There is a time calculation based on % overcurrent that is an industry accepted performance curve. What I am getting at is if you ever have a fuse fail, CHECK IT OUT!!! Or, have someone with some knowledge CHECK IT OUT!!! There is a reason for electrical fires in cars, especially the 308! CHECK IT OUT!

I am working on a 308 fuse block using ATM mini's (blade type) that will take up a fraction of the space a glass tube version will. I just need some time to finish it up. I will post pics when done, should be very simple and tidy. I have designed many elements, caps, rejection caps, lugs, blades, and clips. I will take a fuse over a breaker any day of the week - trust me! Do you remember the Darwin Awards? There was a self-proclaimed "electronics expert" who put a .22 cal bullet in the pig-tail fuse holder of a zillion watt stereo amp in his truck. Why, you might ask? "to troubleshoot a damn fuse that kept blowing". Long story short (play on words), it was a direct short, the bullet got hot enough to discharge - into one of his cahoona's. THis is a true story because our company got sued. Why? For designing a fuse holder that could accomodate a .22 cal shell. I will not go on my lawyer rant, because that is another thread. My point, again, current draw = heat. Heat = flames. Have someone check it out.

Jim

BTW, tell your wife you obtained some good technical information today - a slow blow is a good thing.

 

Dave,
The spade terminals are nickel plated brass (at least they should be). There is bright nickel and reqular nickel. Regular looks alot like aluminum, and solders like crap. Aluminum will not hold form on a clip, that's why I say it should be brass. If it is aluminum, take it back. I could get into aluminum/non-ferrous electrical interaction....but I will not! Long story short - it's not good. If you put enough heat to the nickel plating, you can get solder to flow. However, do it the easy way and just take a round file (preferably, square corner would also be fine - just be careful) and file away a little stripe on the terminal down to the brass. It will solder up just fine. BTW, there is nothing wrong with the jumpers, you did a nice job!
Jim

 

I have never had any problem soldering them. Maybe you got a different kind?

 

This was on Discovery Channel, "Mythbusters" and they could replicate the story.

 

First, thanks Jim for bringing some professional expertise to a topic that just never seems to die (unlike the car with a bad connection).

I've had a few issues with the fuel pump fuse so I just cleaned my fuse blocks. I haven't soldered them yet. I found out a brass wire brush works well on both new fuses (call me paranoid) and the clips. Fiberglass pencils are good in a pinch and I carry one in the glove box. THe aerosol spray for normal electronics doesn't work on the fuse blocks worth a hoot.

The only issue I see is the Fuel pump clip is much darker (almost blue/black) from the rest of the 'copper' clips and I can't polish it like the rest. I suspect because of the current flow.

I also decided to lightly coat the contacts of the fuse & clips with "non-corrosive" grease. It doesn't seem to impact the impediance (I checked with a meter) and I'll keep an eye out to see the overall effect.

Jim, I'll be waiting to see pics & posts of your new design.

Thanks!

PS - my g/f is quick to chime in that it's best to have a no-blow rather than either a fast or slow blow I guess I have to re-educate her on the risks of no circuit protection.

 

Clyde, LOL!!!! Out of all the fuse jokes I have heard, THAT is a new one! BTW, the discoloration could indeed be caused by the brass being annealed by heat. It will not cause any diferences in conductivity, to an extent. HOWEVER, additional heat will cause the clip to lose its "set", or to avoid using metalurgical nonsense, it will get soft and pliable. The other byproduct is that it will age-crack and become more brittle at the form. Too many tweaks at tightening clip will cause it to break. Can you see what is happening? With no spring left in the clip to hold the fuse securely, the electrical connection is compromised. We get more heat and more damage. Then we get flames - obviously the worst case.

Bert - did you mean to say they could NOT replicate the story? I only saw the litigation reports, not the resulting judgements. I never heard different, so I assumed it was true. I do know the test lab did some temperature tests with the pigtail to find out how much heat it could produce in a dead short. Those bakelite holders can shake off a TON of heat.

Jim

 

They could replicate the story, they fired a bullit time after time by shortening the headlights. However, first they needed to install heavier wire because the original wire was to thin and would melt before the bullit went off. That's why they said the myth was busted, because they couldn't see it happen in real life, you should sent them your version of the story.

 

It's about reciprocity with the g/f, dude!

This .22 in a fuse block was a 'P.S.' photo, published in Road & Track long ago...as an electrician I found it hilarious and had it in my office for many years!

I hadn't heard the story about it going off....I think that'd be a stretch...

 

That discoloration IS from heat buildup........

The best product to increase conductivity between metal plates is called "Cool Amp", IIRC.....

It is a rub on silver plating used in 600V + switchboards..

Noalox is used on aluminum, to prevent oxidation and subsequent loss in conductivity.

Now ya'll quit rubbin' on those Ferrari fuses, and pay your g/f some attention! LOL!

 

FWIW, I replaced my troublesome fuse blocks, sure enough damaged by overheating at the Fuel Pump circuit, after 25 years....

I went back with OEM Ferrari blocks, knowing what the alternate BUSS units were worth.

The new blocks, I fugure, are good 'till 2030......may outlast the fuel supply!

Of note, I DID have to put in ONE jumper at the top of ONE block where the later superseeded part did not match my '77 308GTB........but that wasn't a big deal........

There are several stryles of the OEM European fuses, some are open, and there ARE some that are glass barrel, and these have better tips.....stainless????

 

I'll check out the "Cool Amp".

BTW: on rubbing the g/f & ferrari....I must just be confused.

 

BWAAAAAAAAAHAHAHAHA!

THEY started it.......with the Slo blo thing! Not ME!!!!!!

We like the Fast Acting ones.....it leaves less smoke in the room!!!!!

 

We DON"T recommend bullets.........just jam a solid rod in there!

Brings to mind the emergency repair, of wrapping them in foil from your cigarette pack! Desperate times call for desperate measures........

 

Hey Big Tex! From what I can gather, you have probably used a few Class J's and CC's in your carreer! Those were my babies. The other lines that I was intimately involved in were the 1/4" glass, 5mm glass, ATC, ATM, and MAXI and tons of holders and clips. Later came the tiny surface mount stuff. Then it all went to China - but that's another story. As far as the fast acting causing less smoke.... The test facility had 1" bullet proof glass for the control and observation area. The tests took place aprox. 75ft away. They had to replace several panes of glass over the years. Ear and UV eye protection was a MUST for the high voltage stuff. Always lots of smoke - for the demo's! Some of the high voltage fuses were incredible designs and you never knew anything happened. Anyone who works with electricity needs to see this stuff. It will scare you safe!

Ahh yes, the cig foil wrapped fuses.... I work on guitar tube amps ("not another hobby!!!!") and I see at least one a month. Also reminds me of the penny behind the screw in plug fuse (for you oldsters - like me)!

Thanks Bert, I did not know this incident received such notoriety! I think some comment was made about thinning the gene pool!
Jim

 

At least the guy from the truck would have difficulties in transferring his genes to a next generation.

 

Hey Lopealong!

Yep, I go all the way to 15KV..........

I have a friend in an old house that has some pennies.......knob and tube in the attic as well.......his occupation? Fireman with the City of Austin!!!!

Funny, about the tube amps!!!! Of course, with those guitar players "the show must go on!" Buddy Guy was real cool last month, signed a Strat for my boy, if he ever earns it!

Fuses are our friend. Although the one case rupture I've had on a large 600V set sure caused a BIG mess! Blew the covers right off a Main Board in a Marriott. Burned some start up guys.

"Class J, all the way" seems to be the specification of choice these days!

Although there was this hottie with Littlefuse for awhile, sure had us considering equals!!! Know who I'm talking about? She's not there anymore.


Imagine my embarressment after towing my Ferrari home 200 miles across Texas, to have the voltage probe reestablish continuity to the fuel pump!
Just jamming it into the block had it running again! Geez, an expensive lesson!

Big slice of humble pie.................

 

Keep an eye out for a nice Fender Amp then, for Lil' Bull........!

And now back to our 12V application discussion....

Lopealong you know we have Fchatter TubeGuy on here..ya'll should talk!