I think I have an electrical short?

[bobvonryan]

I have a 26 foot Cruisers, Inc. with an AQ290 DP outdrive. I put in a rebuilt engine this Summer and ever since I have had dead or low batteries (dual). I have had to keep it on a charger all summer. When I put the voltage meter on the hot alternator lead I get 13.7 volts. The indicator on the panel says 12 volts or less. I cleaned all the connection between the alternator and the batteries and it doesn't seem to matter. I put a new Die Hard in a few weeks back and it was nearly dead today when I went to check on it. Someone had shut off the breaker to my boat so the charger wasn't on. BTW, I have a dual bank charger hooked up to both batteries. Any chance the charger could be sapping the batteries when not connected to power? I'm Stumpt! I can't figure it out. Anyone got any ideas? Thanks!

 

[Bondo]

Re: I think I have an electrical short?

I put in a rebuilt engine this Summer and ever since I have had dead or low batteries (dual).

Ayuh,.... My guess is, somewhere along the way you screwed up the wiring while doin' the swap,...
I'd suggest you backtrack to find the problem....

 

[EddiePetty]

Re: I think I have an electrical short?

.....isolate to one battery energizing your boat, remove either battery cable and connect an amp meter between the disconnected cable and the battery post, note the meter reads an amp draw. Begin isolating circuits by pulling fuses/tripping breakers. When the meter zeros...there's the culprit circuit. Now it's hand-over-hand in that circuit to find the draw.

 

[Alpheus]

Re: I think I have an electrical short?

Thats exactly what I was gonna say. Excellent troubleshooting tip.

Thats how I found out my stereo was killing my battery in a week...

 

[EddiePetty]

Re: I think I have an electrical short?

......Thats how I found out my stereo was killing my battery in a week...

.....not to mention those of us that have left the radio on with the volume turned down, the Garmin still on with the cover on or left a cabin light on in the head!!!!

 

[cr2k]

Re: I think I have an electrical short?

13.7 is a little on the low side for your alt. should be more like 14, low voltage could also mean low amperage. Are you dual batteries charging thru an isolator of some kind or trying to charge both together?

 

[wire2]

Re: I think I have an electrical short?

If you don't happen to have an ammeter, a small 12 volt lamp (interior) will also show a draw.
Wire it in the same, remove one cable, put it between post and clamp. A slight draw will make it glow, a large one will make it come on bright.

 

[bobvonryan]

Re: I think I have an electrical short?

Thanks guys, all of you! I remember noticing one time (a while back) that when I hooked up the battery it shot a spark just before the lead touched the battery terminal. That says to me something is drawing power, now I need to find it. I just found an automobile diagnostic tool amongst my cousins effects (he passed away) I inherited. I looked through the tools user manual and it does have an ammeter capability. I will try it out as soon as this big blow leaves the Boston area late this weekend. I think I must have connected a positive lead to ground somewhere when I put the new motor in, but I have double checked everything and can't seem to find it. Perhaps with the right tool I can.

 

[Alpheus]

Re: I think I have an electrical short?

If you put a pos. to ground the wire or fuse would have burned out.

Make sure you hook that ammeter up in series, if you don't you will blow a fuse in the meter...

 

[bobvonryan]

Re: I think I have an electrical short?

Well I only had a few minutes today so I took a multimeter to the boat and did some more checking. I disconnected one battery and then measured the voltage across the battery. I only get 12.5 volts across the battery with the motor running. It turns out the the battery selector switch has 13.7 volts coming into it. Shouldn't I be reading 13.7 across the battery or is it just 13.7 at the positive to ground? Anyway it's a Guest battery selector switch and it did not appear that there is anyway to take it apart to clean the contacts. So I guess I just run it on one battery until I take it out for the winter.

 

[Alpheus]

Re: I think I have an electrical short?

You should be reading the same voltage at the battery. Sounds like you got a high resistance between your switch and battery. Take off all the contacts and clean them up. If that does not work you may have a bad switch...