Thread: Wiring Gurus.... LED GAUGE.. HELP

Originally Posted by rufus2007

Now I know the car is supposed to convert AC to DV and this unit is intended to read AC up to 20V. There is a DC gauge but it reads amps and I want voltage. Am I doing something wrong or is this gauge broken?

Here is a drawing from the seller. The DC input is easy from anywhere in the car, but where the crap do I get the AC current to monitor voltage?

You won't - cars run off of DC power (12V or 24V).

The only thing that generates AC voltage is the alternator, and it converts it to DC voltage before the power gets to the thick wire attached to the alternator.


Also, the eBay link isn't clear whether this device is a Voltmeter for measuring voltage, or an Ammeter (amp-meter) for measuring amps or current.

On the back of the unit you got, is there a mark next to one of the numbers, such as the V or A indicators?

That is what I figured. Amazing how you can work on so many projects and FUBAR something so simple....

Originally Posted by lostreception

eBay: Brand New 3½ Blue LED Digital Volt Panel Meter DC 0-20V (item 270103917979 end time Mar-29-07 08:07:10 PDT)

thats what u needed

Lostreception's right.. you got the wrong model.

The one above can be used to measure the DC voltage in the system.

The + and - wires are attached parallel to the DC + -, just like you had in the wiring diagram.



I'm not sure if you could get one to measure the DC Amps (current), as they only had ones that went up to 2A.

Actually, they do have a analog DC Amp-meter:

eBay: Brand New Analog AMP Panel Meter + Shunt DC 200A (item 270100086415 end time Apr-13-07 23:54:30 PDT)


I forget how the shunt plays into it, but amp-meters are wired in series with the + line.. the meter goes in between the + power source and your device such as the amplifier or carpc power supply.

I'm just going to order this and have both: eBay: 200 A 200 V DC BLUE LED Solar Panel Battery COMBO Meter (item 230107353374 end time Mar-27-07 12:29:28 PDT)

Originally Posted by rufus2007

I'm just going to order this and have both: eBay: 200 A 200 V DC BLUE LED Solar Panel Battery COMBO Meter (item 230107353374 end time Mar-27-07 12:29:28 PDT)

That's good, but make sure you check if it includes the required Shunt.

"IMPORTANT: A 200A 75mV Shunt must be used for the meter to read/measure current (amps)."


Shunts are devices you insert in series with the circuit to measure the current:

Make Your Own Shunts

This is the shunt you need:

eBay: SHUNT Resistor for DC 200A 75mV Current Meter Ammeter (item 230058588837 end time Mar-28-07 11:27:22 PDT)

lol this shunt business is making me forget all about monitoring Amperage.

Originally Posted by rufus2007

lol this shunt business is making me forget all about monitoring Amperage.

You can always get the shunt later if you wanted to measure the amperage..