Voltmeter reads alternator or battery output?

[timkee330ci]

As title, may i know what does the voltmeter in the instrument read? Battery or alternator?
Mine read below 11v now, Is it time to change the battery? It's five years old now.
Car still cranks an starts ok but central lock stopped working.

 

[BennyD]

As the gauge still reads when the engine is stopped, I thinks it's reasonable to assume it reads the battery voltage. FFIW, I leave mine plugged into a trickle charge battery conditioner when she's parked up.

 

[CatmanV2]

Given that the alternator is connected to the battery, I can't see that the question really makes much 'sense'.

They are not terribly accurate, though, so unless you are getting issues that lead one to think the battery is flat, it's probably OK.

What's the problem with the central locking?

Benny, you sure they read when the car is off? Never noticed that!


C

 

[Gixerboy]

The Answer is both, the voltmeter measure "circuit potential difference" so when the car is stopped it "reads" battery voltage, however when the car is running the alternator puts out 13.8v. So with all heavy draw circuits switched off, e.g lights & heated window, that should be what it reads. As current using equipment is switched on it may drop to around 12.5v.

If the voltage on the gauge does not change from engine stopped to running, it indicates a charging fault with the alternator.

Hope that helps
Dave

 

[BennyD]

Benny, you sure they read when the car is off? Never noticed that!

With the ignition on and the engine not running it will display the battery voltage.

 

[beau]

mine seems to be the most inaccurate thing ever, sits at 10 with igntion on, the goes upto 12.5 when running, then drops to 11 after a while, all checked on volt meter and its normal (12.6v and 14.5v)

 

[CatmanV2]

With the ignition on and the engine not running it will display the battery voltage.

Oh yes, of course!

C

 

[CatmanV2]

mine seems to be the most inaccurate thing ever, sits at 10 with igntion on, the goes upto 12.5 when running, then drops to 11 after a while, all checked on volt meter and its normal (12.6v and 14.5v)

Mine wanders off on its own as well. I've learned to ignore it, mostly.

C

 

[davy83]

The voltmeter does read the battery voltage and indeed this is the same as the alternator voltage when the engine is running. The alternator charges the battery by raising the voltage which is how you do it with lead acid batteries. The meter in the 3200 is more or less useless, and although you do some times think its telling you some thing useful, i would not make any decisions based on it, it drifts all over the place. Get a simple digital meter and measure battery terminals in the boot directly. You will most likely find its all working properly, should be 12v engine off and 12.5 to 14 volts engine running depending on the state of the battery and what else is switched on.

 

[timkee330ci]

Thanks alot guys for the reply and information. I will try to measure directly at the battery.
The central lock stopped working then i found the voltmeter dropped to below 11v, so i guess it may be connected.
Fuses are checked to be intact.
Now the central lock works intermittently. ANother problem to be solved.

 

[CatmanV2]

Thanks alot guys for the reply and information. I will try to measure directly at the battery.
The central lock stopped working then i found the voltmeter dropped to below 11v, so i guess it may be connected.
Fuses are checked to be intact.
Now the central lock works intermittently. ANother problem to be solved.

What do you mean 'intermittently'?

C

 

[Chrisbassett]

Now the central lock works intermittently. ANother problem to be solved.

That could just be a stiff mechanism on one of the locks, mine was intermittent so I had the solenoids replaced. But maybe just a case of opening the door panel and checking for free movement of the locks.

 

[BennyD]

It might be worth checking the earth straps, especially the main battery earth. My oil pressure gauge was doing weird things which turned out to be a dodgy engine earth strap.