voltmeter reads

[Juan]

A quick question:

my voltmeter (at the cockpit panel) reads 12.5 when I turn the key to the ignition position. Once the motor starts, however, it goes to 15. Is this a normal read? I never paid attention to this before.

thanks,

Juan

[Ron Hill]

Juan : The Volt meter in the engine instrument panel is not a super exacting instrument!!

You need to take a good multi meter and check those volt reading before and after starting the engine - for the best accuracy.

About the only thing I used that engine panel Voltmeter for was to check that the glow plug circuit dropped the reading about 2 volts when engaged.  Then I knew that circuit was working. 
Otherwise I used the Link 10 battery monitor to monitor Volts, Amps and Amp hours!!

A thought 

[Stu Jackson]

Ron's right.  Check the voltage AT THE BATTERY BANK with a dvm.  If it is higher than ~14.6 or so, please let us know right away.

[Ken Juul]

12.5 volts is the battery charge.  Once started the depending on the charge state of the batteries the voltmeter should rise indicating the alternator is charging the batteries.  15 seems high, but as others have said, check at the battery bank with a quality meter.

[Juan]

thanks for the advice!

Ron you were right. The voltmeter at the cockpit is not very accurate. When the motor is on it reads almost 15 volts. But when I measure the volts at the batteries with a digital multimeter the reading is 12.9 v.

Juan

[Ron Hill]

Juan : What you look for at the batteries steady state (no charge or discharge for 24 hrs) is 12.75V = 100% charge.

When the engine is running look for a voltage no greater than about 14.5V

These are basic readings!!   

[Roland Gendreau]

I would suggest reading the voltage at the meter itself to determine if the meter is faulty - a colleague's meter had similar behavior and replacing the meter fixed the faulty indication.

[Clay Greene]

12.9 volts at the battery with the engine running seems low - I would expect to see voltage in the 14.1-14.5 range if the alternator is working properly and you have good connections running from the alternator to the battery (alternator-starter-battery switch-battery if you have the factory installation).  Yet you said that the voltmeter at the panel showed almost 15 volts so I am not sure if your reading at the battery is correct.   Might be something to investigate to make sure that you are getting good recharging voltage at the batteries from the alternator.