30A Strip Fuse for Blower? - Page 3 - PeachParts Mercedes-Benz Forum

layback40 · #31 10-14-2011, 03:05 AM

Quote:

Originally Posted by Billybob

Forget it you can't help Brian et al on this, he was just blowing smoke everyone see's it and anyone with any ounce of sense knows it.

Like a penny in a fuse box, yeah just like that except it's not, where'd you get that from the Looney Tumes Lectricity comic you been studying!

Blowing smoke while the OP was blowing fuses !!

vstech · #32 10-14-2011, 01:38 PM

ok, everybody on here know this.
this forum is for EVERYBODY! there are those who are capable of soldering a fuse, and IF there isn't a problem with their blower then it's not usually a problem, BUT recommending to the general public to just solder a broken fuse is unwise. it may work fine, it may not. all the arguments in the universe will not get me to trust a repaired fuse to give my car the protection that the factory deemed necessary.
now, if you want a quick dime store repair that WILL be a good choice in a pinch, purchase one of those fuse holders with the 4" #10 copper wire leads on them, and drop in a 30 amp spade connector fuse. install THAT under the screws on your car, and I'm happy. (heck, even better would be to use that solder you have been recommending and tin the ends of the wire on the holder so the stranded wire doesn't slip out from under the screw!)

I don't have a dummy load tester to verify the strip fuse will blow at the same amperage and in the same amount of time soldered vs un-soldered. so thinking that the additional mass of the solder blob will alter the criteria of the link, I'm going to recommend doing without a blower until correct fuse is available, or installing a readily available fuse holder to bypass the link.
you could even purchase a MAXI-FUSE holder with #6 leads on it and use a heavy maxi fuse in the 30 amp range for sure fire protection!

bustedbenz · #33 10-14-2011, 04:46 PM

Quote:

Originally Posted by vstech

now, if you want a quick dime store repair that WILL be a good choice in a pinch, purchase one of those fuse holders with the 4" #10 copper wire leads on them, and drop in a 30 amp spade connector fuse. install THAT under the screws on your car, and I'm happy. (heck, even better would be to use that solder you have been recommending and tin the ends of the wire on the holder so the stranded wire doesn't slip out from under the screw!)

THIS is what I did to mine when it went. When my 30A fuse in the external holder went out, it went out so slowly that the first time I knew I had trouble was when I smelled smoke coming from the dash vents. When I got to checking to see why the car was smelling like it was on fire, I discovered that the non-modified, correctly rated 30A strip fuse was so hot it was melting the "rubbery plastic" holder that MB put it in, up on that piece of metal it mounts to. The plastic was burning and smoldering rather than the fuse blowing. I decided that this wasn't a state of affairs I even wanted to mess with, and removed the whole mess and just put a fusible link in with a 30A spade fuse acceptor on the thing. End of problem.

pmckechnie · #34 10-14-2011, 08:02 PM

I have read thru this discussion and think some one needs to explain how and why a fuse works. The most basic electrical formular in electronics is I=E/R where I is amps, E is voltage, and R is resistance. A fuse has resistance. When amperage goes thru a resistance, heat is generated. The more amperage, the more heat. The fuse is designed to melt when the designed amperage is exceeded.
Now someting that needsto be explained.

If you cut a 30A fuse in half, the resistance will be 1/2. If the resistance is cut in half, the amperage it can carry will be doubled. In other words, you will have 2 60A fuses.

Take the ohms law formular above and plug in 30A for 'I' and 14V for 'E' and find 'R'. It will be a very low number. Now recalulate again but use 14V for 'E' as before and the resistance calulated above devided by 2 for 'R' and you will come out with 60A for 'I'

Here, let me do it for you. I=E/R 30=14/R R=14/30 R=.4667 ohm

Now Half of the same fuse I=E/R I=14/(.4667/2) I=14/.23335 I=59.995 AMP

If you have an OHM meter senitive enough, you can use a piece of wire smaller than the wires you are protecting and cut it so it has .4667 ohm resistance and you will be safe. ALL wire has resistance.

A fuse that is soldered back together will have a different resistance depending on how much solder is used and how much of the original fuse is coated. Was the fuse amperage changed? Yes it was. How much? Who knows. Would I use it? NO.

We work on cars quite often that someone thinks a bigger fuse is better. It either totals the vehicle or the bill will be out of site. The fuse is to protect the wiring it serves. If the fuse is bigger than the wire it protects then the fuse and the wire reverse their functions and the wire heats up and melts. Usually melting into other wires that then melt into other wires and on and on.

Please try to understand the point and proof from the above calulations and don't mess with fuses.

Paul
(Paul's Auto Electric) We work on the ones the other shops don't want.

sixto · #35 10-14-2011, 08:11 PM

Quote:

Originally Posted by pmckechnie

If you cut a 30A fuse in half, the resistance will be 1/2. If the resistance is cut in half, the amperage it can carry will be doubled. In other words, you will have 2 60A fuses.

Depends which way you cut the fuse in half and what you do with the halves. If you cut a across the small constant cross section, you ostensibly have two shorter fuses of the same rating.

Sixto
87 300D

vstech · #36 10-14-2011, 08:22 PM

I'd go with the math from the electronics expert...

it's not the thickness of the fuse element that gives the protection, it's the TOTAL fuse size and length and thickness that protects the circuit.

pmckechnie · #37 10-14-2011, 08:27 PM

Quote:

Originally Posted by sixto

Depends which way you cut the fuse in half and what you do with the halves. If you cut a across the small constant cross section, you ostensibly have two shorter fuses of the same rating.

Sixto
87 300D

Please read the above again. A fuse has resistance and is measured from one end to the other, not just one part of it. It is this resistance that determines how much amperage it can handle. If you cut the fuse to make 2 shorter fuses, the resistance from one end to the other end is less than the resistance of the whole fuse. if the resistance is less, it can handle more amps.

Paul

sixto · #38 10-15-2011, 01:53 AM

Quote:

Originally Posted by pmckechnie

Please read the above again.

Easier to buy the proper fuse

But thanks for being patient.

Sixto
87 300D

ah-kay · #39 10-16-2011, 03:39 AM

Quote:

Originally Posted by pmckechnie

if the resistance is less, it can handle more amps.

Paul

If I cut the fuse lengthwise, the resistance will be half. Would it carry more amp and become a higher rated fuse?

If I cut the fuse vertically and have a mean to join it back again. Would the fuse be of less resistance and become a higher rated fuse?

I am not a scientist nor a fuse expert. It is a complicated subject and I am just saying your theory does not hold water.

pmckechnie · #40 10-16-2011, 09:28 AM

ah-kay, you are correct, my theory doesn't hold water, but the facts do hold electrons. This isn't something I made up, it is fact.
I was going to go deeper into this subject but decided to drop it. I don't have the time to explain in more detail and you wouldn't have time to read it. I am just trying to share some of what I have learned over the last 50+years. Don't mess with fuses, use the correct one and be safe. A drop of solder will probably work fine. If it only covers 10% or so of the area of the fuse then worst case would be the fuse would handle 33 A instead of 30A. No big deal. Actually it would probably be less amps as the solder will melt at a lower temperature and the fuse would open up again. It is possible you could just push the ends of the fuse back together and the first time it is used, it will arc and weld itself back together and again be a 30A fuse.

Paul

Brian Carlton · #41 10-16-2011, 10:02 AM

Quote:

Originally Posted by pmckechnie

Please read the above again. A fuse has resistance and is measured from one end to the other, not just one part of it. It is this resistance that determines how much amperage it can handle. If you cut the fuse to make 2 shorter fuses, the resistance from one end to the other end is less than the resistance of the whole fuse. if the resistance is less, it can handle more amps.

Paul

I agree with this conclusion.

However, I suspect the difference in resistance is very slight and the casual observer would conclude that the shorter fuse blows at the same amperage level as the longer fuse. The errors in measurement and the tolerancing of the thickness of the metal can easily be larger than the difference in resistance.