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  #16  
Old 01-23-2013, 12:16 PM
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Yeah you would need to look at the I^2t characteristic of the new metal combo. If that solder melts (phase change is a great way to remove heat) for example, it could allow excess current to flow longer.

Id almost be more inclined to put a 16-18ga jumper without insulation in there than a soldered fuse. Something that will indeed melt at overcurrent... THough Vdrop will likely be large.

Just get the right part...

If you can find a really HD fuse holder that uses a standard ATC fuse, you may be able to get away with that... But Id want the leads to be 10ga or heavier...
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  #17  
Old 01-23-2013, 12:20 PM
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Just to be clear: I'm not saying that continual use of a jumper is a good idea. I'm saying that sometimes these fuses fail and an immediate replacement is not available and the engine needs to be started and won't start without the glow plugs. In those circumstances, jumping the terminals is a good idea. A better idea is getting a supply of the 80 amp fuses in advance and keeping them in the glove compartment
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  #18  
Old 01-23-2013, 12:28 PM
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Quote:
Originally Posted by JHZR2 View Post
Yeah you would need to look at the I^2t characteristic of the new metal combo. If that solder melts (phase change is a great way to remove heat) for example, it could allow excess current to flow longer.

Id almost be more inclined to put a 16-18ga jumper without insulation in there than a soldered fuse. Something that will indeed melt at overcurrent... THough Vdrop will likely be large.

Just get the right part...

If you can find a really HD fuse holder that uses a standard ATC fuse, you may be able to get away with that... But Id want the leads to be 10ga or heavier...
Heavier, definitely.
I'd want at least #8, preferably #6 to be able to handle an 80 amp maxi fuse.
remember, the circuit only has 80+ amps on it for a second or two, after that, the amperage drops to around 30 amps, so the fuse needs to be time delay, 80 amp max. I think a time delay 60 amp maxi fuse would work, as the strip fuse is likely designed to fail at a certain temp when the amps hold over 50 amps for x seconds... and a maxi fuse is designed to handle it's rated amps for a long time...
look at the size wire feeding the GP relay... it's nearly #6 in size.

I do know that when the 5cyl loops are upgraded to pencil, #10 works to feed them, but there are dangers with the first short section of that system.
a maxi fuse holder change, should be large enough to prevent heating of the supply wire, and not melt the relay, or the fuse holder...
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  #19  
Old 01-23-2013, 12:43 PM
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I would rather solder it then jump it with a wire, any wire.

Quote:
Originally Posted by JHZR2 View Post
Yeah you would need to look at the I^2t characteristic of the new metal combo. If that solder melts (phase change is a great way to remove heat) for example, it could allow excess current to flow longer.

Id almost be more inclined to put a 16-18ga jumper without insulation in there than a soldered fuse. Something that will indeed melt at overcurrent... THough Vdrop will likely be large.

Just get the right part...

If you can find a really HD fuse holder that uses a standard ATC fuse, you may be able to get away with that... But Id want the leads to be 10ga or heavier...
Let me ask you guys a question. If you could move the connection bridge nearer and screw down half of the busted fuse, would it provide the same protection as the old fuse. When you make do, you make do, and no harm is done in this case. In a fuse, the weakest link will break when over-amperage.
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W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

2 x 87 300SDL
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  #20  
Old 01-23-2013, 01:03 PM
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when a wire used as a fuse fails, it gets unbelievably hot. white hot in actuality, that's THOUSANDS of degrees... when a fuse material fails, it only gets as hot as the metal it's made of will melt at.
I totally agree, a soldered fuse would be safer than a copper wire. but a jumper wire attached for starting, with the hood open, and you standing there, and removed when the car is started, is my choice, rather than going to the trouble of soldering an old fuse.
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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!
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  #21  
Old 01-23-2013, 02:43 PM
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I'd question why it blew...

I'd look for any chaffed or bare wires on the GP harness. I don't think a bad GP would cause it to blow...
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  #22  
Old 01-23-2013, 02:56 PM
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Maybe it didn't blow, it just broke. Heat stress fracture.

Make sure there's a little slack or "dip" in the new strip fuse when you tighten down those 2 screws. It needs expansion and contraction space as it heats up for each use. A fully taut fuse can heat stress itself into two parts much sooner and die an early death... before it ever fails for carrying over-current for too long which is the normal failure - or would that be success? - mode of a fuse.

Look into an ATC fuse you see the serpentine shape inside the plastic window, same reasoning.
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  #23  
Old 01-23-2013, 04:00 PM
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Quote:
Originally Posted by scottmcphee View Post
Maybe it didn't blow, it just broke. Heat stress fracture.

Make sure there's a little slack or "dip" in the new strip fuse when you tighten down those 2 screws. It needs expansion and contraction space as it heats up for each use. A fully taut fuse can heat stress itself into two parts much sooner and die an early death... before it ever fails for carrying over-current for too long which is the normal failure - or would that be success? - mode of a fuse.

Look into an ATC fuse you see the serpentine shape inside the plastic window, same reasoning.
I've had a new GP fuse blow in only a few days. I wonder if not prebending it caused it?
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1983 D-50 Power Ram 4x4 "Mitsubishi" 2.3 turbo diesel
assorted gas powered crap and motorcycles

RIP: 1984 300TDT, 1982 300TDT, 1984 190D 2.2, 1992 300D 2.5, 1987 300TDT, 1982 Maxima LD28, 1983 Maxima LD28, Isuzu C223 P'ups X3, 1983 Holiday Rambler 6.2 Banks turbo diesel, 1984 Winnebago LeSharo 2.1 TD, 1985 Allegro 6.5
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  #24  
Old 01-23-2013, 04:14 PM
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GP fuse blew because of over current. Over current is caused by, very likely, one of the 12v feed is touching the chassis. BTDT.

The fuse will work for a long time whether it is screwed on taut, pre-bended, slight dipped or whatever. Use your common sense as there is nothing to it. A fuse is a fuse and how it is screwed on should not make a difference. It is possible for a fuse to develop a hair line fracture, but it is very different from a blown 80A fuse. A blown 80A fuse would have a 'big' crack, you cannot miss it.
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Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

2 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.
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  #25  
Old 01-23-2013, 06:17 PM
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Indeed, it's hard to miss anything having a big crack! Ahem.
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  #26  
Old 01-23-2013, 06:36 PM
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Another option would be to replace it with a "maxi" fuse holder and fuse, thus modernizing the system a bit. Or even a DC automotive circuit breaker -- they're surprisingly cheap.
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  #27  
Old 01-23-2013, 08:14 PM
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Quote:
Originally Posted by vstech View Post
when a wire used as a fuse fails, it gets unbelievably hot. white hot in actuality, that's THOUSANDS of degrees... when a fuse material fails, it only gets as hot as the metal it's made of will melt at.
I totally agree, a soldered fuse would be safer than a copper wire. but a jumper wire attached for starting, with the hood open, and you standing there, and removed when the car is started, is my choice, rather than going to the trouble of soldering an old fuse.
My 240D had a copper wire as the glow plug fuse for at least 15 years until I replaced it a few years back. The fuse blew one day at my grandfather's office so he used a strip of copper wire to "fix" it. He was an electrical engineer so I guess it was okay.
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  #28  
Old 01-23-2013, 08:25 PM
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NEVER, EVER use a higher rating fuse.

Quote:
Originally Posted by gatorblue92 View Post
My 240D had a copper wire as the glow plug fuse for at least 15 years until I replaced it a few years back. The fuse blew one day at my grandfather's office so he used a strip of copper wire to "fix" it. He was an electrical engineer so I guess it was okay.
It works does not mean it is OK. You can replace all the fuses in the fuse box with a metal bar and the car will run. It does not mean it is OK.

As I have said, in a pinch, you can solder the blown fuse as long as there is a section of old fuse in the circuit. I am not advocating this practice but it is doable in 5 minutes when you need the car and the new fuse is not there yet. Obviously replacing it is the best solution, <$2 part.

Bottom line - have I done it before, Yes. Would I do it again when I have no new fuse, Yes.
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Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

2 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.
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