Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 09-08-2015, 03:15   #31
Moderator
 
Paul Elliott's Avatar

Cruisers Forum Supporter

Join Date: Sep 2006
Posts: 3,866
Images: 4
Re: Using ohmmeter to determine when to replace wiring

Quote:
Originally Posted by dave948 View Post
if you not willing to invest $10,000 or so in test equipment your never going to accurately be able to test your wiring.
Perhaps, but all you need is a $20 digital voltmeter and your normal working loads to adequately test most boat wiring. Spend $200 more and get a DC clamp-on ammeter, and then you've got it pretty much covered. You won't be able to solve every conceivable problem, but you will be able to find and fix the vast majority.

Of course you have to know what you're doing, but the fundamentals are pretty easy.

And no. I wouldn't use resistance measurement as my primary troubleshooting technique. Turn on the loads and measure the voltage at the load and at the battery. Measure voltage drop across connectors and terminals. Consider your ground wiring as just another part of the circuit -- many times ground problems go un-diagnosed since we think of "ground" as something special.
__________________

__________________
Paul Elliott, S/V VALIS - Pacific Seacraft 44 #16 - Friday Harbor, WA
www.sailvalis.com
Paul Elliott is offline   Reply With Quote
Old 09-08-2015, 03:38   #32
Certifiable Refitter/Senior Wannbe
 
Wotname's Avatar

Cruisers Forum Supporter

Join Date: Jan 2008
Location: South of 43 S, Australia
Boat: Van DeStat Super Dogger 31'
Posts: 7,331
Re: Using ohmmeter to determine when to replace wiring

+1 Paul E.


Quote:
Originally Posted by dave948 View Post
Finally a subject I can say I know what I'm talking about, I've made a living at it for the last 30 years.
1st if you not willing to invest $10,000 or so in test equipment your never going to accurately be able to test your wiring. One of the key pieces of equipment you will need is an ultra low ohm meter, one that places a 10 amp load on the circuit will work well. This is a $6000 meter that needs to be plugged in and uses a four wire system to calculate the resistive loss of the leads....l.
I guess prices change

Not sure what part of the world you are in but here in Oz, one can get a 4 wire lo-ohm 10A, portable meter including calibration certificate for $1,500. Good for 100 micro-ohms. I priced one only last week for work.

Add a 600 or 1,000V megger and a middle of the road Fluke MM, say $1,000 and you are good to go around $2,500.

Nevertheless, I reckon the OP can sort out most wiring issues with a chinese MM for less than $100 if he uses his noggin.

YMMV.
__________________

__________________
All men dream: but not equally. Those who dream by night in the dusty recesses of their minds wake in the day to find it was vanity: but the dreamers of the day are dangereous men, for they may act their dreams with open eyes, to make it possible. T.E. Lawrence
Wotname is online now   Reply With Quote
Old 09-08-2015, 04:03   #33
Registered User
 
bill good's Avatar

Join Date: Oct 2006
Location: Brisbane Australia
Boat: sold
Posts: 721
Re: Using ohmmeter to determine when to replace wiring

For interest only, the black wires on my boat turned to copper dust. Put it down to the die in the plastic insulation. Neg & pos both were switched. All black wires replaced.
__________________
bill good is offline   Reply With Quote
Old 09-08-2015, 06:55   #34
Registered User

Join Date: Sep 2012
Location: Everywhere
Boat: Cutter, 31'
Posts: 150
Re: Using ohmmeter to determine when to replace wiring

Quote:
Originally Posted by dave948 View Post
Copper wire has no moving parts, left alone it will out last you and your boat. Green and black copper wire conducts just as well as bright shinny wire, that's why it's used as a wiring method, unlike aluminum, copper salts conduct very well.
Most problems are going to come from switches, fuses, terminations and just plain bad installations. Physical damage can also be an issue.
The majority of problems come from years of equipment upgrades with no regard to upgrading the 10 year old system your hooking into. Boat builders don't give you much in the way of head space when it comes to your electrical system.
Upgrade your system as needed to support new loads but very rarely do properly fused wires fail. Keep your terminations tight and clean but the wire in between will be the last thing to fail.
Nice. Thanks.
__________________
esarratt is offline   Reply With Quote
Old 09-08-2015, 06:59   #35
Registered User

Join Date: Sep 2012
Location: Everywhere
Boat: Cutter, 31'
Posts: 150
Re: Using ohmmeter to determine when to replace wiring

Quote:
Originally Posted by Wotname View Post
Nevertheless, I reckon the OP can sort out most wiring issues with a chinese MM for less than $100 if he uses his noggin.

YMMV.
Yep. Been using an el cheapo Radio Shack one for years.
__________________
esarratt is offline   Reply With Quote
Old 09-08-2015, 13:29   #36
Moderator
 
Paul Elliott's Avatar

Cruisers Forum Supporter

Join Date: Sep 2006
Posts: 3,866
Images: 4
Re: Using ohmmeter to determine when to replace wiring

Quote:
Originally Posted by dave948 View Post
Green and black copper wire conducts just as well as bright shinny wire, that's why it's used as a wiring method, unlike aluminum, copper salts conduct very well.
What??? Cupric Oxide and other oxides of copper are poor conductors. They have about 10x or 100x the resistance of copper. A little bit of oxidation on the surface of a wire won't have much effect, but heavy oxidation will kill a connection.

Have you ever had a crimped connector pull off a wire that has been in a salt-air environment? I've seen wires that have turned to powder from oxidation. These corroded contacts can be a fire hazard, if they work at all.

Tinned wire isn't required by the electrical codes, but it sure holds up better than untinned copper to the forces of oxidation.
__________________
Paul Elliott, S/V VALIS - Pacific Seacraft 44 #16 - Friday Harbor, WA
www.sailvalis.com
Paul Elliott is offline   Reply With Quote
Old 09-08-2015, 15:03   #37
Registered User
 
Cadence's Avatar

Join Date: Dec 2008
Location: SC
Boat: None,build the one shown of glass, had many from 6' to 48'.
Posts: 6,058
Re: Using ohmmeter to determine when to replace wiring

Quote:
Originally Posted by Paul Elliott View Post
Perhaps, but all you need is a $20 digital voltmeter and your normal working loads to adequately test most boat wiring. Spend $200 more and get a DC clamp-on ammeter, and then you've got it pretty much covered. You won't be able to solve every conceivable problem, but you will be able to find and fix the vast majority.

Of course you have to know what you're doing, but the fundamentals are pretty easy.

And no. I wouldn't use resistance measurement as my primary troubleshooting technique. Turn on the loads and measure the voltage at the load and at the battery. Measure voltage drop across connectors and terminals. Consider your ground wiring as just another part of the circuit -- many times ground problems go un-diagnosed since we think of "ground" as something special.
Paul makes some great points. A $20 meter is all you need with a little bit
of knowledge. Also checking the ground is as important as the supple, what goes in has to come out to be simplistic.

Are you having problems? Speaking about rewiring seem extreme.
__________________

__________________
Cadence is offline   Reply With Quote
Reply

Tags
wiring

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Can You Determine Correct Packing Drip-Rate at Low / Idle rpms ? sgtPluck Propellers & Drive Systems 5 10-01-2015 23:33
Marieholm 26 - How Do I Determine its Age ? VP21 Monohull Sailboats 2 06-09-2010 11:35
How to Determine if Buffing Would Return Shine bilgedawg Construction, Maintenance & Refit 2 28-06-2010 10:35
I need a "source" to determine entry fees HAwkcharter Atlantic & the Caribbean 5 19-12-2007 14:18
Help Determine Spinnaker Fabric Weight Celeste General Sailing Forum 4 21-11-2006 17:17



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 16:30.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.