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-   -   Autohelm Wiring Issue (http://www.sailnet.com/forums/electrical-systems/57162-autohelm-wiring-issue.html)

Hesper 08-17-2009 04:29 PM

Autohelm Wiring Issue
 
When I bought my good old boat, it came with a Raymarine ST4000 autohelm. Wires (grounds, presumably) ran to the metal fuel tank. Probably not a great idea, but whatever. Last winter, I had to replace the tank as it sprang a leak and the yard guys put in a plastic tank.

Since then, the Autohelm doesn't work. Looking below, I saw wires dangling unattached, so I attached them to various screws that seemed to be used as grounds for other wires.

Now, when I turn on the Autohelm, instead of darkness and silence, the controller lights up with the correct compass heading, but when I engage it, I get a few clicks from the neighborhood of the wheel, but nothing else.

Anybody got any bright ideas?

btrayfors 08-17-2009 05:07 PM

From the clues you provide -- which are really very little to go on -- it would seem that someone attempted to use the metal tank as a source for the negative return for the autopilot.

That's a no-no. Autopilot motors (and, in fact, virtually all connected devices aboard) need their own positive and negative feed wires. It's generally not OK just to "connect to a ground somewhere."

Also, the "wires unattached" in the plural is worrisome. Normally, there'd only be a single ground wire.

With more info on your setup, it might be possible to diagnose the problem if the above isn't it.

Bill

Hesper 08-18-2009 02:59 PM

Bill,

Thanks for your comments. I know my information is sketchy, but I haven't really had time to crawl around the engine room yet and I am a total ignoramous when it comes to electrical systems. Are you saying that every device should have a wire that goes back to the negative terminal on the battery (or, more likely the bus on the fuse panel)? I always thought that a ground could be, for example, to an engine block. I probably need to do some reading.

btrayfors 08-18-2009 03:19 PM

Yes, each device should have it's own negative return wire going back to a negative bus somewhere. Only exception(s) would be for devices that should be wired directly to the batteries (bilge pumps, SSB radio, etc.).

There should only be ONE big ground wire running to the engine.

Bill

hellosailor 08-18-2009 03:54 PM

Hesper, if you don't have the installation manual it should be available online. Find out how it is SUPPOSED to be wired up, then make your wiring be the same way.

At a certain point it will call for plus-and-minus power connections and quite possibly a ground as well. If there's no common ground bus in your boat, this is a good excuse to run one, at least as far as the autopilot and instruments.

A spool end of tinned 'ground braid' or tinned large-conductor wire (or "machine cable" which is similar to battery cable) can often be found as surplus on ebay for reasonable prices, so you can be generous with where and how you run it.

flatracker 08-21-2009 06:14 PM

I think your ground connection
 
You said your ground connection was origionally to the fuel tank, which is of course the first no no. After you had the new tank installed, and dangling wires, no auto pilot. Then a hook up and a display, but no drive motor. I think you have a poor ground connection, that allows enough current for the display, which takes very little power, but not enough for the motor, which takes 3 or 4 amps. I am in total agreement that you should go over all the wiring. Anyone who would use a fuel tank as a ground, would do just about anything.

floatsome 08-29-2009 06:05 AM

I'd suggest drawing a schematic for the boat's current wiring, and then start updating. Start drawing the charging system/engine/house main supplies, and then track down the smaller circuit connections. Check wire condition as well as routing. Consider revising the wiring to properly sized and serviced ground and positive busses rather than opportunistic attachments to whatever. Only one sufficiently large ground cable to the engine is a good idea in my amateur opinion, not ground wires attached to the nearest nuts and bolts on the engine. It's a bigger job than it seems, but pays big dividends in reliability and peace of mind.


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