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Catalina/Capri 25/250 Sailor's Forums

Catalina 25 Specific Forum

Main Electrical Short

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KiteKraemer
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191 Posts

Initially Posted - 07/13/2010 : 21:04:48

Hey Everybody, hope summer is going well and fun for all.

Ive got a short when I flip the main. Was wondering where to start and what to look for. I did a search and found this thread:

http://www.catalina-capri-25s.org/forum/topic.asp?TOPIC_ID=21838&whichpage=1&SearchTerms=short

I was looking (hoping) to get a short diagnosis / procedure of things to look for when this is happening.

Not sure why it happened, cuz we didn't go fiddling around with any wires, and no matter how many fuses I put in the main, they blow.

Thanks to you guys, I'm sure this will be no problem to fix!

Unicorn
78•C25•SK
Hood River, Oregon
http://www.eclipsefilms.com/unicorn.jpg

Edited by - KiteKraemer on 07/13/2010 21:07:00

redeye
Master Marine Consultant

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3476 Posts

Response Posted - 07/14/2010 : 03:46:10

<< Thanks to you guys, I'm sure this will be no problem to fix! >>

No Problem, quit flippin that main...

It this your panel?

the 12v or 120?

My 1984 boat does not have a "main" so I'm not sure what you are referring to.

Got any pictures?

Edited by - on

KiteKraemer
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191 Posts

Response Posted - 07/14/2010 : 09:49:22

Its very close, kinda looks like this one,

http://3.bp.blogspot.com/_c2bWSCrhGWU/SpSc5ZKLmzI/AAAAAAAAAC4/lXCSDJTTLPg/s320/OldPanel.png

except where theres a light on this one, mine has a fuse like the rest.

My question is more of a general one though, aside from looking around and "seeing" loose wires, or an actual short - this has already been difficult to pinpoint, as it didn't just jump out at me. Do I need any testing equipment? I started by visually inspecting, but I didn't see anything at all that stood out.

Edited by - KiteKraemer on 07/14/2010 09:54:33

aeckhart
Master Marine Consultant

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USA
1709 Posts

Response Posted - 07/14/2010 : 10:19:44

Soooo, which one of the fuses blows? Once you have that pin-pointed shouldn't you be able to trace the wire to the problem from the back of the panel? Am I little nieve here?

If I were to guess though, I'd bet your short is in the deck plug to the mast wiring or the plug to the mast wirng itself.

Edited by - on

redeye
Master Marine Consultant

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3476 Posts

Response Posted - 07/14/2010 : 12:30:13

<< where theres a light on this one, mine has a fuse like the rest. >>

You do have a main fuse then.

Take all the fuses out, except the main one. Turn on the power and put each fuse in one at a time till the main blows.

You could have resistance that the main would not blow until 2 or 3 or more are in, but that is less likely.

Anyhoo.. put one fuse in at a time, and remove checking each circuit. When the main blows you have a start for which circuit is shorting.

If you can get a shot of the back of the panel that could help.

Then you could use the others until you finish repairing the short.

Edited by - on

redeye
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3476 Posts

Response Posted - 07/14/2010 : 12:55:01

You could not even have a short ( but you probably do). If your main fuse is a smaller rated fuse, your whole system could have built enough resistance to cause it to be drawing more that the rated amps for that main fuse.

Sometimes people put a small 1-5 amp fuse in the main and it will blow when you turn everything on.

What is the rating of the main fuse?

But .. first find the one circuit that is shorting.

Edited by - on

redeye
Master Marine Consultant

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3476 Posts

Response Posted - 07/14/2010 : 13:17:31

You would want a 15 amp fuse in your main, something like this.

http://www.newark.com/bussmann/bk-agx-15/electronic-cartridge-fuse/dp/02J8547

But for testing you can put a 5 amp in the main and in each circuit and plug each in one at a time and see which one is shorting.

Sometimes people get lazy and don't see the amps and put a 5 on the main and when they finally turn everything on the main blows.

And then they might keep trying to put another 5 amp ( or less ) in the main and think they have a short just because it keeps blowing.

Edited by - on

redeye
Master Marine Consultant

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3476 Posts

Response Posted - 07/14/2010 : 13:28:04

<< Do I need any testing equipment? >>

So I reckon you're not big on electrical stuff? You don't have a tester? Do you have a friend that does electrical?

Edited by - on

Voyager
Master Marine Consultant

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USA
5376 Posts

Response Posted - 07/14/2010 : 21:06:53

KK -
Looking at your switch panel, I notice that the master switch does not have any fuse. It does, however, have an indicator light.
So, which fuse is blowing when you flip the switch? Do you have an in-line fuse from the battery to the electrical panel? Or does one of the five fuses on the panel blow? If so, which one?

Taking a page out of Ray's book, if you turn all the switches off, replace the blown fuse, then ONLY turn on the master switch, does one of the fuses blow? If yes, which one?

If not, then turn on the spreader switch. Does this blow the fuse? If so, then your mast plug and spreader circuit is hosed.

If not, then turn off the spreader and turn on the Anchor switch. Does this blow the fuse? If so, then your mast plug and mast top light or circuit are shorted.

If not, then turn off the anchor and turn on the bow light. Does this blow the fuse? If so, then your mast plug and bow light or circuit are shorted.

If not, then turn off the bow light, and turn on the cabin. Does this blow the fuse? If so, there are seven segments of wire you have to deal with (if you have six cabin lights). Before you check the wires, take out all the bulbs, as one may be shorted, and then it would just be a bad bulb, and not the circuit.

If not, then turn off the cabin lights and turn on the running light. Does this blow the fuse? This circuit can be difficult to diagnose, since the distances are long. Mine was botched up by the anchor pulling on the cable in the anchor locker.

If you take these steps and you can't narrow down the source of the problem, you might have either a wiring error on the back of the switch panel, or you've got a random piece of metal crap stuck in the wires that may have flown in throught the dumpster.

Is your VHF radio directly connected to the Master Switch? If so, could there be a wiring error, chafed insulation or bad plug on it?

Last thought, each circuit takes about 5 - 6 Amps. So all five circuits might take about 25-30 Amps. The main fuse should be rated around 30Amps

Edited by - on

redeye
Master Marine Consultant

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3476 Posts

Response Posted - 07/15/2010 : 06:05:38

<< notice that the master switch does not have any fuse >>

Kite said his panel was "Like" the one pictured, except he had a fuse where the little light was.

<< except where theres a light on this one, mine has a fuse like the rest. >>

<< The main fuse should be rated around 30Amps >>

I found my wiring to be 16 gauge on my boat, and I would not fuse greater than 20 amps for 16 gauge wire. With wire that old, I'd start fusing at 15 to see if you can find anything that is excessively loading a circuit.

http://www.powerstream.com/Wire_Size.htm

This American wire gauge (AWG) table lists the limit at 22 amps for 16 gauge.

Anyhoo... Kite... take some pictures and everybody could be more specific. I would not ( and did not ) work on my panel or just about any of my electrical without taking a picture of it first, and then getting a specific plan together before changing the wiring.

Also... look at the wire you have and find the wire gauge.

Edited by - on

KiteKraemer
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191 Posts

Response Posted - 07/15/2010 : 16:46:29

I will take some pics this weekend. I can only visit my boat on the weekends being that I live in Portland, Or
and my boat is in Hood River. Traffic is a Bust. My main blows every time, with no other fuses in the panel.
I'll bring the camera and take some pics this weekend! Thanks Crew!

Edited by - on

Dave5041
Former Mainsheet Editor

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USA
3758 Posts

Response Posted - 07/15/2010 : 17:25:25

if your main blows with all other fuses removed, the problem should be on the panel itself unless a PO has added a circuit directly to the main. The main should only go to the hot side of the other circuits. Corrosion, an old wire. or an abraded wire could be providing a path to ground or to the unfused side of the distribution buss.

Edited by - on

Voyager
Master Marine Consultant

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USA
5376 Posts

Response Posted - 07/15/2010 : 19:55:31

Ray
Thanks for the clarification on the fuse in the panel. You'd have to eyeball the rear of the panel to look for chafed insulation or inadvertent crossed wires, then look at all the circuits to see whether any circuits (like the VHF, depth gauges or FM radio/sound systems) are directly wired to the main, and have a fault.

Wire gauge calculation is a little bit more complicated than you indicated in your post.

It's a two-variable thing: amperage x distance, with an acceptable voltage loss of round trip determines required wire gauge.

See: http://www.delcity.net/documents/catalog/1_wire_cable.pdf

For example, if you have a 2A or 24w light bulb located 10 feet away from the panel, you might accept a 0.6 volt (5%) loss at the bulb. If you used 18 gauge wire running 20 feet (round trip distance) you would have less than 0.6 volt drop.

If, however, you needed to run 5A for navigation lights 20 feet each way (40 ft total), you'd need to use 12 Gauge wire. While I never intend to drive 40A to the panel, I used 8 gauge wire running 12 feet each way, or 24 feet round trip. At full current, I still have a less than 5% voltage drop.

When I flip on all the switches, I pull about 30A. So, I've got ampacity to spare. I found a 40A automotive fuse for the line to the panel.

I never expect to blow the fuse under normal operating conditions.

Edited by - Voyager on 07/15/2010 19:57:03

redeye
Master Marine Consultant

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3476 Posts

Response Posted - 07/16/2010 : 03:49:39

<< I never expect to blow the fuse under normal operating conditions >>

yepper... me too.. I'd put a 30/40 amp in there any day, but I'm tryin to get him to blow one. And it sounds like he did.

RE: the bigie fuse, I thought the issue was not voltage drop, but amp ratings for the wire it has to go through. Trying not to heat them up. Same thing with my panel. 16 gauge on the jumpers to the fuse holders is right about the limit for what the board could push through it. Course it just means that wire is just gonna heat up some if I had hooked up everything, the big stereo and the disco ball.

Anyhoo... his main alone is blowing, so it sounds like something is wired directly to the main or crossed on the board like you said. I wonder if the fuse holder could rust up and short out.

Might be something he can get to easily, just a little dumpster diving.

Edited by - on

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