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  Fishfinder/GPS goes on and off at random

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Author Topic:   Fishfinder/GPS goes on and off at random
Basshole posted 09-03-2009 03:24 AM ET (US)   Profile for Basshole   Send Email to Basshole  
Hi all, my 21 Conquest has an older Lowrance X-85 fish finder which worked flawlessly before I just installed a new Lowrance HDS 7 GPS/fish finder to compliment it. Actually, the X-85 in now intended to be a back up unit and to offer multiple screens of viewing rather than splitting screens.

My problems began immediately after I installed the HDS 7. Now it seems as though when I run through some chop and the boat pounds a little either one or both of my units turns off. Sometimes they re-power up right away but sometimes it can be a while till they re-power. Most of the time the turn off together but occasionally they do it separately.

When I installed the HDS 7 I simply hooked the power leads to the same bus bar terminals that the X-85 was connected to. Also while I was having this issue I took off the instrument panel on the boat to see if my connections came loose only to discover they very intact and quite solid.

The part that is troubling is that the X-85 worked just fine before and I have not done anything to it in particular other than adding the other unit to it's bus bar spot. Could this be the problem? The bus bar is fairly full and there seems to be multiple items linked to any given terminal even though my boat does not have that many electronics on it. Anyone got any ideas on what's causing the problem
other than my lack of experience installing marine electronics? Thanks in advance.

White Bear posted 09-03-2009 02:13 PM ET (US)     Profile for White Bear  Send Email to White Bear     
You have identified the church for your problem, now you just have to find the correct pew. Remember, boats are unlike automobiles - instead of having a nice steel chassis or body to act as a ground, all of the electrical devices on a boat must be served with individual ground wires. Assuming your connections for the power supply are clean and tight, I would suggest that your ground is at fault and that the fault was probably introduced when you removed the instrument panel. Electrical circuits on a 21' boat are really quite simple, but tracking down an intermittent problem such as yours can be time consuming and even though a wire may look good on casual inspection, there may be an internal fault which destroys continuity. Start with the biggest wires from the batteries to the distibution panel, then the smaller wires from the panel to the end users - you will find one or more connections and/or wires that are not performing as they should. While you're at it, this might be a good time to identify all of the wires on you distibution panel and eliminate those that no longer serve any purpose - it will make future fault finding that much easier. Good luck.
Chuck Tribolet posted 09-04-2009 01:27 AM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
It sounds like both devices crap out at the same time. So
the bug is some where between the battery and where they
both attach to the bus bar.

I'd try the following experiment. On the trailer, turn
both devices on (and the Aux switch if they are wired through
it (they should be)). Start at the bus bar and work back
towards the battery. Wiggle the wires in the circuit, rap
on things with the butt end of a screwdriver, and try to
reproduce the problem. Once you know about where the problem
is, zero in on it. You may need a buddy to watch the
electronics while you wiggle.

If you get really stuck, and want to tow to Morgan Hill
(that's about an hour fifteen away for you right coasters),
I'd be glad to have a look.


Basshole posted 09-04-2009 02:16 AM ET (US)     Profile for Basshole  Send Email to Basshole     
Thanks guys. Those are good tips. This weekend instead of fighting traffic trying to leave town I am going to pull the boat out of storage and further investigate and try your suggestions. One thing Chuck is that sometimes only one unit goes out and it seems to occur when it gets jarred. I am determined to figure this out even if it requires me to learn everything about my boat's wiring.
swist posted 09-04-2009 08:57 AM ET (US)     Profile for swist  Send Email to swist     
If you have a ground return problem as suggested by others, then that might suggest that sometimes you have a partial connection with enough resistance to cause one or the other units to shut down due to a low supply voltage condition - this could be quite random depending on the design of the electronics, but would explain why both units don't always fail in sync with each other. In any case, you're still looking for the same thing - a bad or weak connection, and all the strategies suggested still apply.
Basshole posted 09-05-2009 12:24 AM ET (US)     Profile for Basshole  Send Email to Basshole     
Thanks again guys. Since you guys have all mentioned a grounding problem, that got me thinking. I looked up the wiring diagram for the units and overlooked a very important detail, THE GROUND! I just realized from the diagram that the ground wire for the HDS 7 was bundled with some other networking wires I wasn't using and was not connected. Duh! I can't believe I forgot the ground ! I'm pulling the boat out of storage this weekend and am excited to have the solution. Couldn't have done it without the good tips.
roloaddict posted 09-05-2009 12:45 AM ET (US)     Profile for roloaddict  Send Email to roloaddict     
I would check the terminals you crimped on the wires for both units, especially if you were running low on spots to attach to the buss bar and used one terminal for two wires.

Most budget terminals have very short metal(tinned copper)sleaves and as such, have a very small area to grip the wire(s). Pro grade terminals have an additional sleave of larger diameter to crimp on the insulation to give you a strain relief. Nylon insualation is more robust and less likely to split like the Vinyl.

Budget crimpers ($5-$20) are often mis used in the folowing ways: The insulated crimp area is in the dished area(commonly the tip),but most that I have seen used the uninsulated side with the post that is drivin into the center of the terminal, many so hard as to sever the wires inside and create a intermittant connection. Since there is no ratchet under crimping is very easy to do. The results are the same, a less that ideal connection for a vibration prone platform.

Pro Crimpers ($50-$300), are almost universally set up for the insulated termnals exclusively, and have a ratchet that will prevent under crimping. They also have the two sets of crimps in the dies to crimp the wire as well as the strain relief sleave. Mil spec crips will have a dot or two on the crimp to indicate this.

I have used nylon sleaved terminals from AMP, T&B and Waytek. T&B and Molex crimpers have been my trusty sidekicks in the tool box for 25 years. I have fixed and installed thousands of connections with them.

Basshole posted 09-08-2009 11:25 AM ET (US)     Profile for Basshole  Send Email to Basshole     
Fixed it! Everything is working perfectly. It must have been a bad crimp job because I removed and re-crimped some new loop style connectors instead of the two prong style ones that were on there and they worked much better. I think the prongs on the two prong connectors bend really easily and were not making good contact. I do have a set of cheapo crimper which I now think I should invest in a good pair. Again, thanks for all the good advice. I feel like I learned a lot from this experience.

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