Date:         Thu, 13 Dec 2001 14:51:05 -0500
Reply-To:     David Beierl <dbeierl@ATTGLOBAL.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         David Beierl <dbeierl@ATTGLOBAL.NET>
Subject:      Re: Battery Isolators vs. Relays
Comments: To: Julian Burden <julian.burden@SYMPATICO.CA>
In-Reply-To:  <01ad01c1840a$ed2949d0$3b47fea9@grumpy>
Content-Type: text/plain; charset="us-ascii"; format=flowed

At 02:18 PM 12/13/2001, Julian Burden wrote:
>This is not my understanding of relay failures - I thought that relays were
>more likely to fail closed because the contacts weld together, particularly
>if the current rating of the relay is exceeded! Then we're talking flat
>starter battery in the morning.

Or in the case of my recent experience, an 80,000 lb. boat turning hard to
port until the steering motor fuse blew.  Very amusing to look at the GPS
plot, but a bit of a nuisance at the time.  It was a hydraulic steering
system, so we could spin the wheel to starboard and just about keep up with
the autopilot pump -- but then the fuse would never blow since the
autopilot didn't drive the rudder up against the stops (and because of how
the shipyard in Nova Scotia had wired it, turning off the autopilot didn't
help -- and they'd put the fuse down in the engine room, bless 'em).

I cured it later by putting snubbing diodes across the relays, but it made
our trip back to the States a bit more interesting than otherwise.

You Canadians will be amused by this I think:  the boat had been under
repair in NS for a year, lots of work of all sorts -- and we got under way
without a Robertson screwdriver to bless ourselves with.  Arrrggghhhh!

david


David Beierl - Providence, RI
  http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage"
'85 GL "Poor Relation"