[Public-List] Bizzare electrical problem

[n4lbl]

Try this theory:  1) The starter battery ground failed completely or
developed a high impedance, perhaps from corrosion.  2) The positive
connection from the battery to the radio is fused, but the ground is not
fused.  (Requires checking.)  Then you hit start and the lowest impedance
ground is through the exterior coax conductor, through the grounded
taffrail (??) etc.

If I am right two things are called for.  First, fix the starter ground.
 Second, fuse both positive and ground leads to the radio as near as is
practical to the battery.

Alan
Albin Vega 27 Minke




On Fri, Apr 5, 2013 at 6:51 PM, Glennb <brooks.glenn at comcast.net> wrote:

> Hello all,
>
> Well today as I was prepping the boat for spring I happened to reach deep
> into the aft storage space aft end of the cabin,over the ice box, and
> noticed my aux VHF antenna cable was extremely hot, bubbling the plastic
> core in one one spot.  This occurred where five small coils of excess cable
> were tied off with a plastic electrical tie.  The run of cable from the
> five coils up to the vhf was hot as well, as was the back end of the radio
> where the ant cable plugs into the unit.  The cable connects to a new last
> year  shakesphere emergency/backup antenna clamped to the aft taff rail.
>  The cable runs aft through the storage space, through the stbd locker
> thence into the lazarette where it connects up through the deck into the
> antenna.  The cable  is not connected to anything else on board- and is not
> shorting to any other hot electrical wire.  There are a half dozen positive
> leads running forward, that cross the cable near where the five coils were
> hot, but they are two strand ar
>  e coated marine wire and were undamaged, not energized, and cold to the
> touch.
>
> The radio was turned off.  The circuit beakers were turned off. Nothing
> onboard was energized except the bilge pump circuit, and the engine
> starting circuit.  I had just changed the engine oil and ran the motor for
> about 30 seconds to oil the engine and check oil level, prior to finding
> the heated cable.
>
> After discovering the heated cabling, I shut everything off and
> systematically turned on the engine, circuit breakers  and radio, but was
> not able to duplicate the condition.
>
> What in the world could cause a near fire temp in a VHF antenna cable
> under these conditions??? !!!
>
> Any ideas greatly appreciated!
>
> Glenn
> Dolce 318
>
> Sent from my iPad
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