Teach Me About the Voltmeter

[Knightfall]

Hey guys, so this is the first vehicle I've ever had that's had a voltage gauge. I understand what it measures, but I was curious about how to actually "read" what is says. Is it voltage from the battery, alternator, or another part of the electrical system? My Voltometer tends to fluctuate quite a bit, and sometimes reads about in the lower third of the gauge (I'm not in the truck right now so I don't remember the actual gauge range). Could this be an issue? What about if it reads very high? Thanks for yalls help!

[txab]

Your voltage gauge on the truck will vary, as it is designed to, depending on requirements. No worries

 

Perhaps you should thoroughly read the OM that came with your vehicle

 

 

From your Owners Manual:

 

When the ignition is on, this gauge
indicates the battery voltage.
When the engine is running, this
gauge shows the condition of the
charging system. The gauge can
transition from a higher to lower or a
lower to higher reading. This is
normal. If the vehicle is operating
outside the normal operating range,
the charging system light comes on.
See Charging System Light 0 139
for more information. The voltmeter
gauge may also read lower when in
fuel economy mode. This is normal.

 

Readings outside the normal
operating range can also occur
when a large number of electrical
accessories are operating in the
vehicle and the engine is left idling
for an extended period. This
condition is normal since the
charging system is not able to
provide full power at engine idle. As
engine speeds are increased, this
condition should correct itself as
higher engine speeds allow the
charging system to create maximum
power.
The vehicle can only be driven for a
short time with the readings outside
the normal operating range. If the
vehicle must be driven, turn off all
accessories, such as the radio and
air conditioner.
Readings outside the normal
operating range indicate a possible
problem in the electrical system.
Have the vehicle serviced as soon
as possible.

[tnchevy]

I'm on several different truck/motorcycle forums and you will not believe the amount of questions that could be answered if folks just read their owners manual. To me that is part of owning any kind of vehicle or anything else with moving parts, read the OM and familiarize myself with it.

[Scruggs]

*EDIT: Whoops... didn't see that you already knew how to read voltage.... guess I just read what I wanted to read. I always get excited talking about circuits so I was overly happy to share some knowledge. Maybe someone else will read this and learn a little.

 

 

I'm a Mechatronics Technician at Robert Bosch, so I know a little about electrical circuits. It would behoove you to familiarize yourself with some electrical theory as well as your OM. Its normal to get high and low voltage readings, DEPENDING on where your probes are at when measuring. You just have to remember that Voltage is a "DIFFERENCE OF POTENTIAL ENERGY." THEREFORE: you can read 0V on your volt meter and still have a closed, energized circuit. I don't know how much you know about circuits... not trying to degrade your intelligence, if you already know, then awesome! Just a little FYI if you were unaware.

 

For Example:

 

You should read voltage if you are measuring from a load to ground, because there is a difference of potential between the two.

 

If you have an energized circuit, and you are measuring V on a line coming from a load, and you place both probes on that same line BEFORE the next load, you will read 0V, because there is no difference in potential.

 

If you were to place a probe on the + terminal of a load and the other probe on the - terminal of the same load, you will read voltage because there is a difference in potential from one side of the load to the other, as the load is using power/energy.

 

I could go way more into detail, but there are great youtube videos on electrical theory and how to use a DMM.

 

Any one else want to chime in/ correct me if I'm wrong?

[Vic15]

Pretty sure he's only asking about the volt meter in the gauge cluster.

[Scruggs]

Yeah, guess I should've read the entire post. I get excited to share about electrical circuits so I jumped the gun.

[15silver]

Interesting observation when I installed a voltmeter in my previous vehicle. When accelerating, voltage would drop to below 12V. After research, this is deliberate in that the vehicle stops charging when accelerating. Saves the horsepower from the alternator for passing. Also an Eco initiative. Charges heavier on deceleration, when you are not on the gas.

Havent noticed this on my truck - but then again it has lots of HP to spare.

[fondupot]

Cant we get a sticky thread about this already. I swear its every week someone new asks about the voltmeter.