12 V Gurus..

[frankgrimes]

Hi Guys,

Haven't been out in the boat for 3 weeks, and decided to grab a copy of my marks from my lowrance 5300(Which was working perfoectly fine 3 weeks ago) - I always take both my 5300 and 515 out of the boat after each trip.

Connected 5300, and it wouldn't turn on - Tried the lowrance 515, and it also wouldn't turn on - hmm..maybe both fuses gone? Replaced them both, checked voltage(12.6 on both), also checked voltage on both power cables(Pin 7+8 from memory) that connect directly into back of the units - Also showed 12.6....thought maybe not enough voltage, so started engine, let it run for 5minutes, checked voltage on both(13.5), both untils still will not turn on(Tried with engine running also)

All other elctrics are working fine - VHF, Bilge, Livie pump, nav lights and anchor light.

Took head units to Bias, plugged them in and they both fired up immediately...so it has to be a power issue in the boat?
If I'm seeing 13+volts at both power cables that plug into the units, I'm stumped what to check next?

Mick

[hakuna]

corosion on the plug that connects to the sounder unit/ pins, give them a scrape/ wd40 and try

[snasman]

Look for the earths at the plug

[frankgrimes]

Thanks Guys.

hakuna - Gave them a good scrape with paper clip, and spray still no go on either unit.

snasman - What am I looking for on the earths of each plug?

[frankgrimes]

Got it sorted thanks guys - Tried moving the sounder across to the bilge gang switch and all good....tried the bilge on the old souder gang switch and now that doesn't work.

Would have thought if there was an issue with the switch, I wouldn't have gotten volts at the power-plugs?

[groverwa]

To me it seems like there is a high resistance connection somewhere - mobs of voltage but no current carrying capacity

1. You can try connecting direct to the battery terminals as this will rule out the rest of the wiring

2. Does the motor start OK??

3. Are the battery terminals clean and tight?? By clean I mean all shite and briny and not a dull colour

4. Try a trouble light or globe with leads across the battery direct and then on the terminals of the power cable to see if there is current carrying capacity

Here is something that may help in measuring volt drop acroos battery terminals etc from another thread: -
If you have a multimeter that will read down to millivolts, and even the cheap ones do, then it is possible to check high resistance joints and\or cables as per the attachment which shows the volt drop across the connection from the battery of my Rodeo with the highbeam lights on

There should be a very small volt drop across any terminal or cable and the drop shown in the pic is 3mV or 3 one thousandth of a volt which is good

Corrosion can occur inside the connector that may not be visible or the crimpimg of the connector lug may not be good enough

High resistance connections will tend to feel hotter than normal


Hope this helps

Mike

[finga]

Here is something that may help in measuring volt drop acroos battery terminals etc from another thread: -
If you have a multimeter that will read down to millivolts, and even the cheap ones do, then it is possible to check high resistance joints and\or cables as per the attachment which shows the volt drop across the connection from the battery of my Rodeo with the highbeam lights on

Hope this helps

Mike

Ah, grasshopper was listening...well reading
A good point about the testlamp. A lot of digital multimeters are too sensitive and have not got enough internal resistance for a lot of this sort of work.
The old analogue ones worked OK but the best is a test lamp with a decent sized bulb for this type of fault finding.

Hey Frank...how far down the coast are you??
If your close too me I'll give you a short tutorial on this sort of caper

[frankgrimes]

Cheers Finga - I'm down in Ashmore mate, so prob a bit out of your way, appreciate the offer though!

I'll have a read through few of your old threads on this subject

Mick

[Spaniard_King]

Mick,

Those switches go frequently, changed a few in my own boat recently.

Basically you need a test light to check for power and not a volt meter as you are looking for current flow not voltage.

[Hagar]

Frank

Sounds like your switches are earth switched . If so there is always power at the unit plug all the way back to the switch which is open circuit until operated . Would explain why you had power at both plugs and it operated when you put it onto the other switch for the bilge . Not a guru - using logic .

Chris

[finga]

Frank

Sounds like your switches are earth switched . If so there is always power at the unit plug all the way back to the switch which is open circuit until operated . Would explain why you had power at both plugs and it operated when you put it onto the other switch for the bilge . Not a guru - using logic .

Chris

Sorry but I cannot follow that logic....well I can but it defies all basic wiring procedures that I've ever seen in a boat.
Sounder and plotter not working on one switch so positive lead transferred to the bilge pump switch.
When swapped the sounder works and the bilge pump doesn't when it's on the sounder/plotter switch. (see below quote)
Sounds very much like a faulty switch which was Spaniard King diagnoses.
Just crook/corroded contacts in the switch.
The voltage is there (as seen by a multi-meter with low internal resistance) but there is no capacity for current to flow.
It's a bit like water coming out the end of a 1mm pipe. The water is there but it ain't gunna wash the car.
See it lots....hey Marlin Mike

Got it sorted thanks guys - Tried moving the sounder across to the bilge gang switch and all good....tried the bilge on the old souder gang switch and now that doesn't work.

Would have thought if there was an issue with the switch, I wouldn't have gotten volts at the power-plugs?

Start with the basics (as above) and that usually finds 90% of faults in house wiring in boats.

[Noelm]

the very best home handy man trouble shooting device is a very simple test lead and light, easy to use, cheap as chips to make one and will help even a complete novice fix and trouble shoot all sorts of stuff around the boat, car and trailer, a meter is a great device, but it is more suited to the experienced operator, been in electronics repair and diagnostics for many years, and still drag out the test lamp for doing boaty type stuff.