Voltmeter differences

[David Handley]

I am seeing higher than normal readings on the dash voltmeter (>15 volts steady) while the Silverleaf is steady at <14 volts.  My mutimeter confirms the Silverleaf reading when measured at the battery terminals.  A technician I spoke with mentioned two things (1) dash gauges are typically unreliable (I saw a post once on this site that referred to them as "entertainment", and (2) both my multimeter and the Silverleaf are digital.  He encouraged me to find an analog meter and check the voltage. 

So, I did that.  I dug around in my workshop and found an ancient analog meter that belonged to my dad--I calibrated it on a known 12V source, started the coach and while reading between 15 and 16 volts on the dash, I saw 15.5 on the multimeter at the battery terminals.  The Silverleaf read 13.9.  So, I had the alternator removed and bench checked at a reputable test facility, and it checked good. Never close to 15 volts output.

Not sure what to do now??  I'm puzzled by different digital and analog readings--what's up with that?  Should I be concerned or follow the advice of another mechanic--"Drive It!"

[Fred Brooks]

    David,
I am the RV technician that made the comment "entertainment purposes only" . The silverleaf is seeing the exact info that the engine ECM is seeing. The highest priority is the correct charging voltage and you have done that. You may try adding an additional new ground wire to the dash cluster to lower the resistance if that is the issue. My volt gauge always reads .7 volts less than my silverleaf. The water temp always reads 15 degrees less than the actual temperature. Hope this helps, Fred

[Eric Maclean Co-Admin]

David
In your case your voltmeter is what we in the trade call an optimometer as it's overly optimistic.
It's not uncommon that the gauges are in accurate.
As  Fred stated the Silver leaf is actually reading the ECM inputs if the voltage is good there your good to go.
But for snickers you could check the output term of the alternator with a digital volt meter it will be the highest voltage in the system if it's good so is the rest of the system
If the output is high there is a resistance in the sense voltage wire telling the alternator that it hasn't acheived the voltage regulator set voltage.in which case you will have to check the sense wire voltage at the back of the alternator and find where that wire is connected to determine where the volt drop is.
But if the ECM is reading proper voltage I'd just chalk it up to a bad volt meter and as your mechanic said just drive it.
Hope this helps
Eric