Immediate voltage loss on hook-up

[hangdogger512]

Hey all,
So, I am just finishing a full restoration on a 92 GW Invader with mercruiser 4.3lx (4bbl). Anyway, I was finally ready to put the battery's in today and test the electrical... and problem. Once I hooked up the battery, it immediately discharged completely.

There clearly must be a huge draw occurring somewhere, just hoping that someone can maybe point out a few potential locations? A lot of items got replaced/added in the resto, so I feel possibilities are everywhere (new console dash, new thottle control, new trim tabs, new alternator...)

Any thoughts on best way to track this thing down?

Thanks!

 

[gm280]

First thing I would verify is that you didn't connect up the battery backwards with positive to ground. Second, with that large of a drain, you should have had the wires get really hot. So I would start over and just connect one item at a time via the fuse or breaker panel. In other words, remove all the fuses and or open all the circuit breakers and hook up a fully charged battery. Then add in one circuit at a time to see what is going on.

You can basically do the same without any battery if you own a meter and know how to use one. Then you merely measure the load (resistance) on the positive and ground wires and start removing circuits until you see the resistance go from very low to high. That means that circuit was the culprit. JMHO

 

[hangdogger512]

gm280 thanks for the advice! I do have a multimeter and was planning something step-wise like your suggestion... Just didn't know if I was missing something obvious. Battery terminals were correct.

 

[Silvertip]

Is the battery fully charged. You may think it's fully charged but hook any sort of load to it and voltage drops like a rock.

 

[hangdogger512]

Is the battery fully charged. You may think it's fully charged but hook any sort of load to it and voltage drops like a rock.

Silvertip Acutally, you are spot on. I meant to post an update last week... I started to work on my troubleshooting plan, then thought, hmm, maybe I need to verify these batteries are holding charge period. One was only 1.5 years old, other 2 years old, and both had been on the smart charger/tender during the whole rebuild process (~1year). Low and behold, both were near bone dry and fried. Like a dummy, I forgot to check water levels as they weren't being used, but in reality they were b/c of the charger...

New batterys, a lighter wallet, and my wiring was spot on and all works wonderfully.