[Public-List] Bizzare electrical problem

[pat nolan]

A lifetime accumulation of salt can cause all sorts of electrical gremlins . I once told a guy with all sorts of electrical problems to wash his engine room. He thought that I was nuts , but it cured his problems. Scrub in the hard to get at places . measure with an ohm meter to check for connections.


________________________________
 From: Glennb <brooks.glenn at comcast.net>
To: "alan.schulman at gmail.com" <alan.schulman at gmail.com>; Alberg 30 Public List -- open to all <public-list at lists.alberg30.org> 
Sent: Friday, April 5, 2013 8:29 PM
Subject: Re: [Public-List] Bizzare electrical problem
 
Alan,

Thanks, interesting. The cooked wire does seem to be coincident with my engine start- first time since October.  So your suggestion seems feasible. The only thing I am having trouble visualizing is how the antenna coax is connected electrically to the ground.

i didnt describe the set up completely accurately.  The antenna is actually bolted to the aft SS pushpit, which is thru bolted to the deck.  The antenna lead comes up through the taff rail.  Would the FG hull/deck conduct enough electricity to carry the resistance to the pushpit then back through antenna cable? i suppose the physical connection to the radio frame and radio ground would transmit the ground back to the engine through the master ground buss. Just not sure how the circuit could be made through the pushpit.

I'll go check out the battery and starter ground etc tomorrow or Sunday.  The radio does have a circuit breaker on the positive, but no fuse on any of the negative side.

Thanks,
Glenn
Dolce 318
Sent from my iPad

On Apr 5, 2013, at 7:58 PM, n4lbl <alan.schulman at gmail.com> wrote:

> 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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