280z sitting voltage?

[chaseincats]

4 hours ago, Dave WM said:

I like my amp meter. ?

upgrade to a amp meter ?

I love that word upgrade, I hear it so often when talking about old cars.

whats the benefit of an ampmeter over a voltmeter?

[SteveJ]

29 minutes ago, chaseincats said:

whats the benefit of an ampmeter over a voltmeter?

Don't go there. It's a dark place.

[Zed Head]

3 hours ago, SteveJ said:

Don't go there. It's a dark place.

Dead battery?

[SteveJ]

1 minute ago, Zed Head said:

Dead battery?

Nope, in the 240Z if you lose the ammeter, the car won't start.

[Zed Head]

I was talking about the darkness.  Bad joke.  

Why can't we have both.  Ammeter and voltmeter?

[SteveJ]

8 minutes ago, Zed Head said:

I was talking about the darkness.  Bad joke.  

Why can't we have both.  Ammeter and voltmeter?

Same here. The car is dark with the bad ammeter.

You can have both, but the trick is to find the right spot to wire in the ammeter, probably with a shunt like in the 260Z and 75 280Z (http://www.measurementest.com/2010/08/how-to-measure-current-using-shunt.html). One of the drawbacks to the 240Z wiring is that the ammeter ends up being a weak spot/single point of failure in the electrical system. All of the current from the alternator to the battery flows through it. In theory if that wire got damaged or comes loose from the ammeter, there could be a lot of current flowing to ground in your dash.

I have also seen a 240Z ammeter fail because someone hooked up the jumper cables backwards to jump start the car.

[Captain Obvious]

6 hours ago, chaseincats said:

whats the benefit of an ampmeter over a voltmeter?

The basic difference is the ability to really tell what's going on with the charging system. For example, consider the following...

You're driving along, and all of a sudden, your alternator goes belly up. The voltmeter will still pretty much read the same thing because the battery is at full charge, but an ammeter would instantly start reading a negative charge condition (meaning that you're taking energy out of the battery instead of putting it in).

Referring to the chart posted above in post number (nevermind, we don't have that feature anymore)... somewhere up above earlier in the thread, it shows that the battery voltage is only down to about 12.1 Volts by the time you have already taken half the total charge out of it. So with a voltmeter, it's possible that you wouldn't notice any problem until the battery has been drained down pretty far.

But with an ammeter, it should never be on the "-" side of the gauge when the engine is running. If that ever happens, it's an indication of a potential problem.

All that said.. .As SteveJ alluded to, it's just so much harder to install an ammeter in a system when compared to voltmeters. Voltmeters are hang on anywhere and are a snap to incorporate. And for that reason, the ammeter is almost extinct.

[AK260]

I totally got the dark joke! I was tempted to say that the ammeter shows the balance of The Force - but that would have been truly a dad joke!

Nice description Mr Obvious!

Slightly off topic - I still get post numbers using Tapatalk [emoji848]

[Zed Head]

34 minutes ago, Captain Obvious said:

The basic difference is the ability to really tell what's going on with the charging system. For example, consider the following...

You're driving along, and all of a sudden, your alternator goes belly up. The voltmeter will still pretty much read the same thing because the battery is at full charge

Actually the red light would come on if the alt died, signifying a charging problem.  And the needle goes up when the engine is running and the alt is charging.  So, if you're aware, you'll notice odd needle behavior.

I see the main difference as what their names say - one shows amps flowing the other shows volts.  But it would be nice to see both.  "Gee whiz, there's a lot of current going somewhere".  or "Holy moly, my battery level sure is sitting low".  I just like to have lots of data to think about.

Either way though, you have to look at the gauge occasionally.  "How long has that been going on?"