Voltage Readings

[hd2002hd]

Recently I noticed the voltage readings on the meters of my 400 SD occasionally jump up to a little over 15 volts for a few seconds while underway. I have digital volt meter that is separate and it confirms the same voltage. Typically the voltage runs about 13.2v-13.5v. The last 2-3 weeks I have noticed it jumping up over 14v and sometimes 15v for just a few seconds. It may do this a handful of times on an hour so so run. Any idea what might cause this? Any major concern?

 

[Steve Craig]

Check for any loose connections at the alternator. If all appears good I would suspect an internal diode on the alternator.

 

[hd2002hd]

Would both alternators have a failure at the same time?

 

[mwph]

Any other issues with any other gauges?

 

[hd2002hd]

Any other issues with any other gauges?

No. Just the voltmeters.

 

[Bob & Sue]

Mine with a single engine has always done this, everything has been checked that's possible. I finally last season narrowed it down to when the fridge is in DC Mode then cycles on, most times it's just a 10-20 second spike then back to 13.4-13.8. With the fridge off it never spikes been this way for 6 years now.

It does this on both the Teleflex gauge & the Digital Garmin Chartplotter & Garmin Fishfinder displays..

 

[Steve Craig]

Wasn't aware you have 2 alternators, 1 each engine. Still, the voltage behavior is telling me diode failure (or close). An intermittent load, such as a fridge or AC unit would show a significant voltage drop at the instant of start.

 

[Bob & Sue]

Wasn't aware you have 2 alternators, 1 each engine. Still, the voltage behavior is telling me diode failure (or close). An intermittent load, such as a fridge or AC unit would show a significant voltage drop at the instant of start.

In my case it does show a voltage drop for 1-2 seconds then spikes up higher for 10-20 seconds.

 

[Searaybio270]

Interesting, I have the same issue with a little twist to it. My port will stay right around the 13-14v but when I get under way 15-16v and stay pegged the entire time I am up and running. Can't figure out why.
For sure I will be watching this thread for ideas.

 

[Bt Doctur]

A lot depends on how the manufacturer wired the boat.
place a voltmeter on one of the engine batteries and record the voltage.
Start one engine and with rpm at 1500, record the voltage, shut engine off
Start other engine,with rpm at 1500 record voltage
If you see a voltage rise on both tests, the engine charging systems are combined.
Place voltmeter on the other engine battery and do the same test.

Or Disconnect one battery and see if only one engine starts, and only that engines gauges
work.