Volt Meter issue

I installed 12 volt power in the bed. I posted that in the "What have you done thread.

I have a problem. I installed a volt gauge/dual USB outlet along with two power ports. 10 gauge wire from battery to fuse block in back 10 gauge wire Positive and negative. Positive straight from battery with a 30 amp fuse at the battery. Negative added to the main ground where the battery is grounded under the hood.

25 ft of run.
I am only showing 7.5 volts on the gauge. Thoughts? Is it possible that a smaller gauge wire at the battery containing the fuse is limiting the voltage?

 

A drawing showing how it's connected would help us to visualize what you have. 7.5 Volts is suspiciously close to exactly 1/2 the charging voltage.

 

There can be a voltage drop over a run of wire, but that is a lot.

Is the VM on the power lead or in a circuit beyond the lead?

A fuse should not drop voltage, but a bad connection can.

Voltage is potential. So, the finest gauge wire should not affect it.

 

I ran power to the fuse block I installed in the back and then the volt Gauge on a 3 amp fused circuit from the fuse block.

 

Have you tested your volt meter reading at the battery ?

New volt meter FUBAR out of the box??

I have a volt meter hooked direct to the battery it works fine.

 

Volt meter on the correct setting?

I don't see how you can be running that low of voltage.

 

i am thinking Gauge not meter.

 

https://www.tacomaworld.com/threads...3rd-gen-today.399305/page-12674#post-28361826

This is his other post with picture. OP... have you measured with a real meter? Is the 10awg from front to back fused at the front?

 

Hope this helps. I suck at drawing

 

Yes Voltage Gauge

 

There is an inline fuse (30 amp) right at the battery but the wire gauge is smaller. It runs about 6 inches of likely 14 gauge then connects to 10 gauge all the way back. Negative is 10 for the entire run.

 

The gauge of wire won’t change the voltage in a meaningful way, it will just have an effect in the max current you can draw thorough that wiring. Use your voltmeter and check voltage at the various connections along the run.

 

I’d suspect that either the digital volt meter is off or OP wired the digital voltage meter and the USB adapters in serial.

 

You might want to check the voltage on the end of each connection. Before and after the fuse block.

 

First problem - wonky voltage reading. What happens when you measure the voltage at the battery? (looking for 12 volts-ish) What is the voltage reading at the battery when it is running? (looking for 14 volts-ish)

Second problem - Normally you just attach the ground to the body, frame, or some other solid bit of metal.

Third problem - the fuse won't work in this drawing. The 14 gauge wire becomes your fuse because it can't handle 30 amps. If you put a 15 amp fuse in the circuit it would be ok.

 

First of all running the smaller 14 AWG wire first and then 10 AWG later does not make sense. It should all be the same. I would get rid of the 14 AWG short runs and make everything 10 AWG. The 14 AWG is not rated for 30 Amps.

What is the "switch" before the meter in your diagram ?

In general you should take a hand held meter and walk down the path checking the voltage to isolate where it drops.

My guess would be somewhere at the end between the fuse block, switch or meter. Try disconnecting each one and checking the voltage.

 

Thanks
First - I have not measured voltage at the battery but it coincidentally was tested this afternoon before I did the installation. I am sure if it was low, they would have tried to sell me a new battery.

Second. The ground is attached to the body where the main negative for the battery is attached.

Third - I will try to attach the 10 gauge straight to battery without the fuse.

Thanks again.

 

What brand meter are you using? I’ve seen issues with cheap meters like Klein not reading correctly. Fluke meters are great but expensive comparatively.

Are you reading 12 volts at the battery? Next question, are there any splices? Have you visually inspected the wire at pinch points for damage that could cause the wire to ground?

 

i'm also curious as to how you changed from the 14ga to the 10ga. a bad splice will also cause this.

but i would first verify with a volt meter.


you also don't need to run the ground all the way back to the battery. any ground point at the rear of the truck will work just fine.

 

it's funny because i've only ever had issues with fluke meters reading wrong. running a flir meter currently.