12V Problems

I have a 1997 28 ft express cruiser. I seem to have an ongoing 12v issue that I am not sure how to track down. Here is the basic setup:

1 Group 31 AGM Starting battery
1 Group 31 AGM House Battery.
1 2-bank battery switch.

I've already replaced both 12v fuse buses under the dash, including new fuses and crimped new ring connectors, all 12v is currently working in the boat.

The problem is when I turn the ignition to Aux, I only get about 10-11 volts. This will go to 12V when I start the engine. I will consitantly see the volt meter take a dive when I hit the drive trim in/out and tabs in/out. I also notice a correlation between when the volt meter drops and the temp guage rising. Recently, I've been running with the radar off and GPS only. for the last two weeks, I've noticed the vot meter fairly low while running. I had the admiral go below and shut the fridge off. I could immediately tell when she shut the fridge off because the volt meter jumped from 10 to 12V and the temp guage dropped simultaneously.

So, I believe I have a short somewhere. I suspect it is a result of all of the corrosion I see on the negative wires on anything I look at.

I'm curious how to continue addressing this problem.

My ignition key itself is showing some signs of corrosion, and I've been considering replacing the ignition itself, though I doubt that is the weak link in the system.

Any thoughts??

Re: 12V Problems

I suspect it is a result of all of the corrosion I see on the negative wires on anything I look at.

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Ayuh,.... I believe yer Right,... You have a Ground problem, not a short...

Re: 12V Problems

Thanks Bond-o I appreciate the clarification. Without opening a can of worms, what would be the best way to attack such a problem?

Re: 12V Problems

shrew said:

Thanks Bond-o I appreciate the clarification. Without opening a can of worms, what would be the best way to attack such a problem?

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Ayuh,.... Start with the Shake, Wiggle, 'n Pull Test....

Turn something "On", 'n start yankin' wires, til it lights...

Re: 12V Problems

For one thing, you shouldn't be running any of your accessories off the ignition switch wiring. That should be engine only. What you should do is run an 8 or 10 gauge fused circuit from the battery switch to the accessory fuse panel as power for your accessories, and leave your ignition switch for the instruments and engine only.

Re: 12V Problems

Please allow me to clarify. To my knowledge non of the 12v devices are running directly off of the ignition switch. This is all factory wiring. Also, to my knowledge there are no 12v devices which are not working. I can shake and wiggle all day, there is nothing which isn't currently working which will start working as a result of shaking anything.

The in-dash volt meter will only actuate when I turn the key to to the ACC. position. Now that in itself is probably misleading since that is the onlly word I think of to describe it. The key has an off position, then the first detense position turns on the fuel pump, guages and the alarm tone notifying you it is working. Then the 2nd detense position acutates the starter. All 12V devices work without the key, with the exception of the guages, fuel pump and starter.

I greatly appreciate everyone's feedback.

Re: 12V Problems

The in-dash volt meter will only actuate when I turn the key to to the ACC. position.

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Ayuh,... It Should be on, workin' with the key in the "On" position, 'n Not in the Acc. position....

Put the key in the "On" position, 'n wiggle yer wirin' til ya find the Problem...

Is the Volt meter properly grounded,..??

Re: 12V Problems

They ignition only has 3 positions: Off, On and Start. I was referring to On as Acc. My apologies for the confusion.

Re: 12V Problems

Have you had the house and engine battery load tested? A battery with a bad cell cannot possibly deliver the current demand for high current draw items like your radar, fridge and trim tabs. Do the symptoms appear whether you have BAT 1 or BAT 2 selected? It is also common to see the voltmeter dip when starting the engine but it should not drop below 10.5 - 11 volts while cranking unless as was mentioned, the battery is bad/weak, or there are bad connections in the system. Start by removing, inspecting the cables where they enter the terminal and then thoroughly clean (as in shiny bright) the terminals and battery posts. Then reassemble tightly. If you are using wing nuts, pitch them overboard and use stainless hex nuts. Then remove the other end of each cable and repeat the process. Now you are assured that part of the system is ok. Battery load testing can happen while you have the cables disconnected. Label them so you don't get those screwed up in the process. A bad ground at the battery also means that the voltmeter has a bad ground so it can't read correctly. Cycle the battery switch back and forth to burnish the internal contacts. Contact corrosion can occur if the switch is not used on a regular basis.