Electrical trouble shooting

LeslieTroyer · Mar 21, 2017

Lights and windlass should Wouk fine at 14 volts. Could your battery switch been moved to none and your just reading the alternator output into no load??

skipmac · Mar 21, 2017

LeslieTroyer said:
Lights and windlass should Wouk fine at 14 volts. Could your battery switch been moved to none and your just reading the alternator output into no load??

This is certainly one possibility.

JohnnyMac, what voltmeter were you reading? Was it on the engine panel showing alternator volts (assuming the alternator output goes through a battery switch) or your house electrical panel that shows battery voltage?

Benny17441 · Mar 22, 2017

No simple straight answer without knowing your setup. Start by checking the health of each individual battery. A single bad battery can fool the alternator and bring down a whole battery bank.

Bill Roosa · Mar 22, 2017

yes, check for a bad battery as lights will work at 9 volts. The fact that the lights did not work indicates a very low voltage and after charging the batteries even a little you should be able to get a light to work.

skipmac · Mar 22, 2017

JohnnyMac said:
I was reading the voltmeter on the electrical panel. Both battery switches were on as was the inverter

Sorry, don't understand the reference to the inverter. Do you mean the charger? If you did mean inverter and it was on then that could have been putting a significant load on the batteries. Were any 120V AC loads connected at the time?

Also, how is the panel meter wired? Sounds like it was seeing the alternator voltage but if I understand, the batteries were not. Have you checked the cables on the battery, The cable from battery to the electrical panel? Ground wires from the battery bank and panel? What do you get if you put a voltmeter right on the battery terminals? What does the panel meter read if the batteries are switched on but the engine not running?

Sailgunner · Mar 22, 2017

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skipmac · Mar 22, 2017

Hi Johnnymac,

More questions occur to me. Do you have separate start battery and house battery bank? If you're running the engine then obviously it cranked but sounds like you aren't getting power to any of the house loads so I'm guessing separate batteries?

Then house loads work when plugged in and the charger is working? Obviously the charger is powering the house loads in that case but why isn't the alternator? Are they wired to the same point in the system? If so then I would start suspecting the alternator. If wired to different points then it might be the battery cables or somewhere in that circuit.

SG · Mar 22, 2017

I don't know of a simple explanation for such a number of observations?

When you say the battery wouldn't support the light? What do you mean -- no light? voltage dropped out significantly?

There are potential reasons for certain things happening which may, or may not be linked.

Essentially, if you are going to troubleshoot the system, you want to go systematically through a process of isolating the issues.

For example: If you had a problem in the lighting circuit which was drawing down the battery -- but not causing breaker (or fuse) to trip? What's happening and what else is connect, etc. etc. is critical to understanding what and why.

One needs, more information to really give you guidance or suggestions.

skipmac · Mar 22, 2017

SG said:
Essentially, if you are going to troubleshoot the system, you want to go systematically through a process of isolating the issues.

Exactly! Trying to sort out an electrical problem by hit and miss is almost always an exercise in frustration and futility. Unless the source of the problem is very obvious (melted wires, smoke coming out of some device) you have to have some systematic way to proceed, usually start at one end and work your way through the system.

SG · Mar 22, 2017

LeslieTroyer said:
Lights and windlass should Wouk fine at 14 volts. Could your battery switch been moved to none and your just reading the alternator output into no load??

Simply, no.

First, if that were the case, I think momentarily the voltage would spike...then the diodes on the alternator would die. Then the alternator would do nothing. The cure is replace the diodes or get a new alternator. (Some battery switches have a link that keeps you from having a momentary "off" if you switch from one to two or both to protect the diodes; but you shouldn't be switching you battery switch settings with the engine on unless you know you have a switch that protects you or a the battery on line.

Secondly, you would see only declining voltage as the batteries were drawn down. Shortly, your voltage would float down to something in the 12.8 or so range (maybe a little more, but less than 14 V). From there, it wouldn't return upward at all until the AC charger was activated.

SG · Mar 22, 2017

As for the inverter charger, if you a going through things, Inverter-Chargers often will fry their boards if you do not have a battery connected and activate the unit. (That's not a simple inverter, but a combo unit. Just a warning because long ago I saw that happen.

SG · Mar 23, 2017

You wouldn't have damaged them from what you described. If they are not sealed, did you check the fluids?

Are you sure it's the positive? Usually, for some reason the vast majority of cables are bad neutrals? ;^)))

Hope that is the only issue.