voltage discrepancies

[Miguels]

this is why you don't get your voltage reading from your cigarette lighter. when i installed my singer alternator i would noticed my voltage dipping to 12.8v at idle after running it for a few miles with AC and lights on. i would turn lights and AC off and would jump to 13.1. drive it a few miles and jumps to 13.7v with everything off. Today i decided to test the accuracy of the voltage. i noticed a big difference in my voltage even up to 1v difference. the reading is lower in the lighter but keep in mind that is not accurate to what the batteries are seeing and what the amps are seeing.

[SnowDrifter]

That's why I always say measure voltage where you want to see it from. If you want to know what your batteries are, measure at your batteries. Want to see your amp? Stick the leads in your amp inputs. Alt? Sure no problem. But the cigarette lighter including all the voltage drop of the stock wiring - I don't see being useful in our applications

[Miguels]

exactly and thats where lots of people have.. i have it there because i have no sound system in there yet. once its done its going on the amp

[GassenD]

Hmmm this sound exactly like what's going on with my voltage issues, but even on my dash gauge my needle drops extremely low..

[audiofanaticz]

Before this turns into something its not:

The plug on the smd vm-1 is only there for the people who do not want to fully install a voltage meter or for those that are not confident in doing so, and where or are using other cigarette lighter style meters.

They never came with a plug, and where just wires hanging out of it like other meters but enough people asked for the plug on the end, and the company listened.

It is said in the directions to cut it off for a hard wired installation, and was only added for ease of installation for some users. Hell I use mine like that currently because I havent even started my dash mods yet for the meter since i dont have the rest of the meters I want to install, so its a temp thing.

Any similar style plug in meter will have similar results with voltage drop, and that is not the meters fault (well some it is), but definitely not the VM-1 meters fault as it was tested against many other manufactures meters all shown on 1 board at the same time all reading different voltages from each other except the vm-1 meters that are all consistent and respond to voltage drop instantly.

The reason the voltage drop is present through the cigarette lighter plug is due to the vehicles wiring.

Everything inside the vehicles cabin and exterior lights all get their power from usually a 10 to 8 gauge power wire that feeds off the main fuse panel under the hood (on most videos), and from there it goes into the cabin using 10 to 18gauge wiring harness that go through the firewall.

This rather smaller gauge wire is prone to a higher resistance when the more current is pulled through to power accessories, even if the voltage meter is not on the same circuit, but still coming from that same source such as that main fuse panel supplied with that 10 to 8 gauge wire.

That is why the voltage is different at the source since it is being supplied with 1/0 gauge wiring.

This is also why upgrading that factory wire with a larger gauge cable from your battery to the main fusebox can help even more with dimming even if you already have done the "big 3" upgrade.