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Author Topic:   Electrical Problem Diagnosis
bkelly posted 10-03-2005 09:17 AM ET (US)   Profile for bkelly   Send Email to bkelly  
[The navigation lamps, the VHF Marine Band transceiver, and the horn on my 1987 MONTAUK] stopped working at the same time. I [checked the] fuses [and connections], [but cannot] find [the] problem. Any [suggestions] [on how to diagnose the problem or on what it might be?]
Tom W Clark posted 10-03-2005 09:44 AM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     
Check the circuit breaker or fuse in the stern.
Chuck Tribolet posted 10-03-2005 02:55 PM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
And the connection at the battery. It sounds like everything
BUT the motor has quit, right?


bkelly posted 10-03-2005 04:17 PM ET (US)     Profile for bkelly  Send Email to bkelly     
I still have bilge [and] guages, plus combo SONAR/GPS wired directly to battery. All these are working. Replaced one end of red power lead at battery. Cleaned all terminals. [Checked] the [connections] under the cover to fuse (port side). All looked good.
st posted 10-03-2005 05:07 PM ET (US)     Profile for st  Send Email to st     
To have three electrical/electronic devices not working at the same time tells me that something happened that's common to all those three. As Tom and Chuck replies above: check those obvious thing first; also fuses on top your panel (if you have't done so).

Next; you're going to need to remove that control panel; turn it upside down if possible, and look again those mentioned above if any (hopefully group of 3) positive or ground/return wires came loose from it's terminal or corroded/frayed or open.

If this looks ok; I would trace from either the vhs or horn or light; and trace them backward to the source (usually to the panel above). Basically: any of those needs a battery voltage wire AND a ground/return/neutral wire for them to work.

Good luck!

Chuck Tribolet posted 10-03-2005 05:29 PM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
Guages run off the motor.

Bilge pump may be wired direct to battery, or back to the
master fuse or CB aft.

If tracing the wiring shows nothing obvious, get a multimeter.
Turn stuff on and work your way from the battery to console
to the devices making sure you have "12V" at each step. When
you stop having 12V, look for the problem in the part
you added.

For example (red means multimeter red lead, black means
multimeter black lead, I if don't say where red or black goes,
it means same place as previous step.

Red to Battery +, Black to Battery -.
Red to battery side of master fuse/CB.
Red to console side of master fuse/CB.
Red to whereever the power wire comes out in the console. You may need to extend the black wire to reach the battery on this one.
Black to wherever the ground wire comes out in the console.
and so forth.

Note that there may be more places to check aft than I listed.


bkelly posted 10-03-2005 08:38 PM ET (US)     Profile for bkelly  Send Email to bkelly     
Thanks all I'll let you know how I do!
jimh posted 10-03-2005 11:32 PM ET (US)     Profile for jimh  Send Email to jimh     
Begin your checking at the device which lacks power. Trace the circuit back to the battery. It should be simple to discover where there is a discontinuity.

For testing it is often more effective to use a test lamp which will draw some current. Simple voltage measurements with a high-impedance voltmeter may show voltages present which are actually being fed through high resistances and will not power the load.

Chuck Tribolet posted 10-03-2005 11:54 PM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
The high impedance of the multimeter is was I said "turn stuff

One more thing to check is the bilge pump wiring. Since the
bilge pump works, you know that power is good to the point
where it ties into the main wiring.


17 bodega posted 10-04-2005 05:38 PM ET (US)     Profile for 17 bodega  Send Email to 17 bodega     
you might also try stripping off some of the affected wire ends... if you see brown or black wires, (like I did!) then you see that something shorted. I have had some bizzare things happen like turning on the stern light and having to wait one minute and then it goes on.

steelhead5 posted 10-04-2005 05:50 PM ET (US)     Profile for steelhead5  Send Email to steelhead5     
Check the connection(s) to the negative bus bar. Otherwise pull out your multimeter and start tracing for voltage.
c_mccann posted 10-04-2005 06:24 PM ET (US)     Profile for c_mccann  Send Email to c_mccann     
How old is the boat's wiring? Montauk's are known as pounders and a bit wet, and the wiring takes a beating in the years- loose connections, corrosion, etc. I'd start with the grounds and work to the buss pannel.
jimh posted 10-04-2005 09:07 PM ET (US)     Profile for jimh  Send Email to jimh     
[Edited and moved this article.]

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