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Discussion Starter #1
I know that many have experien

I know that many have experienced this problem in both Boxers and TRs, but this is the first time for me. During the past week, several of my fuses have heated to the point of melting the supporting fuse block. I have diagnosed the problem as one of two events: 1) loose fuse (copper supporting clips not bent close enough together) such that the contact resistance of the fuse to copper upper or lower fuse seat is too great, resulting in substantial heat and ultimately to melting of the plastic block. As this happens, the geometry of the supporting copper tabs distort, further loosening the fuse, and eccentuating the problem into a "positive feedback" condition - as it gets worse, it gets worse.

The second event that has occurred during the past week is where several positive sides of a multifuse combination is connected by a bar, and the upper fuse tab (support) is connect to the bus by a copper rivet. The rivet get loose with time, and the increased contact resistance leads to melting of the block and further distortion.

I have ordered new fuse block and will try to solder or crimp the rivets to prevent this in the future. In addition, I use a small dremel (Spelling) with brass brush to clean the fuse seats in the support tabs, and clean the ends of the fuse, and clean the tabs where the wires connect, all in an attempt to lower contact resistance. Despite these efforts, these wires and fuses get very hot.

Input is appreciated.

Jim S.
 
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Discussion Starter #2
Jim
First I'd check for a


Jim
First I'd check for any shorts in your system,
then I would search your complete electrical system for any loose contacts in plugs, connectors, etc and maybe clean all of them,
and possibly use a contact grease enhancer.
Badconnections can lead to shorts,
fried wires,and overloaded/heated elec systems which then causes problems particularly with the fuse blocks.
 
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Discussion Starter #3
Hi Jim,

I replace both fuse


Hi Jim,

I replace both fuse boxes in my BB 20 years ago...and they're still fine. At the time, I did no modifications to the new boxes.

As Jeff stated above, all other connections...including the crimp connectors on the wires at the fusebox and at the relay panel (beneath the passenger foot rest) should be cleaned and carefully checked for mechanical integrity. I did end up replacing a few connectors at the fuse box wiring.

Although probably not prudent today, I am still using the OE-style BMW/VW ceramic type "open" fuses, though I replace them every couple of years and tweak the contacts, if necessary. Someone previously had posted a link for gold-plated glass type fuse replacements. Probably a good idea, in the long run.

As to the wires getting warm/hot at the fuse boxes...In most cars, I would say that this is a problem. However, it seems to me that some of the headlight wiring at the fuseboxes is a bit on the light side...and these wires do get slightly warm. Not really a problem for me, as I rarely drive the car at night. If, currently, there are hot (temperature-wise) wires at your fusebox...further investigation would be warranted.

Candidly, in the many years of ownership...I have had near zero electrical problems with the car (naturally excluding the power windows).

Regards,
David
 
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Discussion Starter #4
Hi Guys,

Common problem on


Hi Guys,

Common problem on Italian Cars and Older German Cars for that matter.

Generally the problem/s can be traced to High Resistance across a circuit. Heating of the connections in the fuseblock area, from the crimp terminals to the fuse itself indicate resistance heating is taking place (Ohms law at work)...the worse the connection the more heat is generated. When properly designed and built, intentional resistance heating is a perfectly acceptable way to make heat...like in a toaster, but when it occurs unintentionally in a car's electrical system, it can lead to smoldering connections or insulation or worse melted fuse blocks and complete circuit failure.

Heat due to resistance:

Looking at the P = V x I equation, we can see that any time we pass current through a conductor, and there is a voltage across that conductor we will have a power generated. This is also called resistance heating, or I²R loss. If we have a solid connection through wire and connections of adequate size, the resistance is so low, that we can pretty much call it zero, hence no (significant) voltage is across the connection and we have no (appreciable) heat generated.

If however we continue to pass current through a conductor when that conductors "cross-sectional area" has been diminished (which is why I like the 'larger' Gold Plated Fuses in some instances)in some way (a nick in a wire, a loose rivet on a terminal, a worn contact in a switch, or through years worth of corrosion), at some point, we do start generating a significant voltage across the conductor and the resulting heat at the poor connection.

One of the easiest ways I've found to determine if the Fuse Block is the High Resistance culprit is to clean the in and out female terminals and with a new solid double connector temporarily connect the wires together without a fuse and see if the circuit still heats up appreciably. If you now find that the temp has noticably dropped then it's a sure bet the old fuses and fuse block are the main culprit.

There are several ways to go about fixing or upgrading the Ferrari fuse blocks. The only fix I haven't found effective is is trying to repair the old pieces. One the spring clips have been heated to excess they tend to become tempered and lack enough pressure to work effectivly.

HTH's

Regards, JRV
 
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Discussion Starter #5
JRV - right you are. I remove

JRV - right you are. I removed the culprit block and drilled out the copper rivets. I then soldered all of the tabs on each fuse to the overlay holder (effectively eliminating pressure as the resistance solution), then replaced with new aluminum rivets. In addition, the fuel pump power lead was getting extremely hot at the connector. I clipped off the connector and soldered two new wires to distribute the current separately to the two fuses on the block. MUCH cooler now. The solder connection reduced the I2R losses significantly. I have ordered and received 2 new fuse blocks from Jeff Howe in the U.K., but will put them away for the future. My current fuse plastic blocks look like crap, but are soldered and riveted and working much better. Thanks for the input.

By the way -

1) How did you superscript the I2R?

2) Do you know where I can get the decals that sit on top of the fuse block covers? There is a white block and black block. Thanks.

Jim S.
 
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Discussion Starter #6
Hi Jim,

superscriped by for


Hi Jim,

superscriped by formatting- here is an example code from the admin program on formatting mathematical codes:

Mathematical Notation

Tag Description Example Tag Output
<font face="symbol" size=+2>S</font><sup><font size="-1"> upper</font> </sup><sub><font size="-1">lower</font></sub> Sum using sigma notation <font face="symbol" size=+2>S</font><sup><font size="-1">10</font> </sup><sub><font size="-1">i=1</font></sub> i Si=110 i
<font face="symbol" size="+2">ò</font><sub><font size="-1">lower</font> </sub><sup><font size="-1"> upper</font></sup> Definite Integral <font face="symbol" size="+2">ò</font><sub><font size="-1">0</font> </sub><sup><font size="-1">6</font></sup> x dx ò06 x dx


Example

Input: <font face="symbol" size="+2">ò</font><sub><font size="-1">0</font> </sub><sup><font size="-1">2<font face="symbol">p</font></font></sup> sin(x) dx = 0
Output: ò02p sin(x) dx = 0


takes some playing around with or best is to look up formatting using google and find a Graph Site with all the formulas.
-------------------------------------------------

I don't know where to get the decals seperate from the new fuse blocks that come with the covers.

Regards, JRV
 
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Discussion Starter #7
JRV - the new fuse blocks that

JRV - the new fuse blocks that I received from Jeff Howe at U.K. did not have the decals on them.

Jim S.
 
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