Amp meter to Volt meter. How??

[Paul Y]

Morning all,

Have to take my dash out again to put a step up resistor in it to get it to work so wanted to kill 2 birds with the preverbal single stone and look at getting the Amp meter working.

For those following along I purchased a replacement volt meter from a later C10 and fitted it to the stock gauge only to realise what I had actually done was replace my Amp meter with....another Amp meter. DOH!

So, what is the hot ticket for getting a working volt meter in the dash?

Any and all advice gratefully received!

P.

[theastronaut]

I've seen it done before, but what is the purpose of getting rid of the amp meter and swapping to a volt meter?


I use a usb outlet with a built in volt meter in the cig lighter to check voltage and charge my phone in my '66.

[franken]

There's no such thing as a "step up resistor" so no idea what you mean there.
A voltmeter just needs a voltage source and a ground connected with the right polarity.

[Paul Y]

Clarity required.

My tach isn't working so adding a 1kohm resistor between a switched 12 volt source and the tach wire - this is an LS swap - according to the internet the signal from the PCM is not strong enough to drive the tach.

In one of the videos I watched the chap referred to the resistor as a Step Up. Might have got the context wrong but that's where it came from.

As for why Volt over Amp. Dont really fancy having big power wires behind a steel dash, Just in case...

Plus auto wire dont recommend it so just going with them.

I want to get as many of the dash gauges working as possible hence why I wanted to know what would work in the stock dash.

Seems like a later gauge will work after a bit more digging but always keen to hear what others have done.

P.

[RustyPile]

Originally Posted by Paul Y

Clarity required.

My tach isn't working so adding a 1kohm resistor between a switched 12 volt source and the tach wire - this is an LS swap - according to the internet the signal from the PCM is not strong enough to drive the tach.

In one of the videos I watched the chap referred to the resistor as a Step Up. Might have got the context wrong but that's where it came from.

As for why Volt over Amp. Dont really fancy having big power wires behind a steel dash, Just in case...

Plus auto wire dont recommend it so just going with them.

I want to get as many of the dash gauges working as possible hence why I wanted to know what would work in the stock dash.

Seems like a later gauge will work after a bit more digging but always keen to hear what others have done.

P.

Repeating what franken said.. No such thing as a step up resistor.. Technical definition of resistor is: Current limiting device.. It limits current flow, or "steps down" the signal.. So perhaps the guy in the video doesn't understand electricity.. A 1K ohm resistor (1,000 ohms), as resistors go, isn't much resistance.. Perhaps the guy in the video doesn't understand electricity. Could be the tach signal is too strong and a dropping resistor is needed.. If indeed, a stronger signal is required, a transistor and related components would be used to create a signal amplifier circuit.

I'm not offering this as a suggestion to your problem.. Rather, I'm explaining how electricity and electronic components actually work.

Always remember this... Just because it's in an internet video, doesn't mean the information is correct.

[ray_mcavoy]

Originally Posted by Paul Y

Clarity required.

My tach isn't working so adding a 1kohm resistor between a switched 12 volt source and the tach wire - this is an LS swap - according to the internet the signal from the PCM is not strong enough to drive the tach.

In one of the videos I watched the chap referred to the resistor as a Step Up. Might have got the context wrong but that's where it came from.

That sounds like you're describing a pull-up resistor --> https://en.wikipedia.org/wiki/Pull-up_resistor

Originally Posted by Paul Y

As for why Volt over Amp. Dont really fancy having big power wires behind a steel dash, Just in case...

Plus auto wire dont recommend it so just going with them.

These trucks use a shunt type ammeter so there are no 'big' high-current carrying wires behind the dash. The 'shunt' (which is just the regular charging system wire that runs from the + battery terminal, across the radiator support, to the bus bar on the horn relay) is what carries the current. The stock setup does, however, use smaller gauge wires that are connected directly to the battery & charging system without any fuses. That aspect can easily be made safer by simply adding some small inline fuses like GM did with the 67-72 trucks.

American Autowire likely doesn't recommend / support the stock ammeters with their 'Classic Update' series because of the way they have configured the charging system. They use considerably heavier gauge wire, which can handle higher currents, but also reduces the sensitivity of the stock ammeter if used as a shunt.

When changing over to a voltmeter, the easiest way to wire it up would probably be to hook it up to the power & ground wires for the temperature gauge (located right next to it).