Voltmeter

[davery]

If one was to install a voltmeter, which fuse should it connect to? I was thinking the ignition, but there appears to be no open connections. Could I use fuse #11 or #12?

[focodave]

A voltmeter does not need to be fused, so you can connect it to any of your fuse terminals that are on the battery side of the fuse box and you will be fine.
I hooked mine up to the key chime circuit, so when I insert my ignition key, I get a voltage reading on the battery before I even try to start the car.
I disconnected my key chime because it gets on my nerves, but you could keep it (the key chime) connected if you want to and the voltmeter will still work fine.
The voltmeter is wired in parallel to whatever you are going to be connecting it to.
Voltmeters are very, very high-impedance, low current draw devices -- so they don't need to be fused -- and -- they don't affect anything they are wired in parallel with.

[davery]

A voltmeter does not need to be fused, so you can connect it to any of your fuse terminals that are on the battery side of the fuse box and you will be fine.
I hooked mine up to the key chime circuit, so when I insert my ignition key, I get a voltage reading on the battery before I even try to start the car.
I disconnected my key chime because it gets on my nerves, but you could keep it (the key chime) connected if you want to and the voltmeter will still work fine.
The voltmeter is wired in parallel to whatever you are going to be connecting it to.
Voltmeters are very, very high-impedance, low current draw devices -- so they don't need to be fused -- and -- they don't affect anything they are wired in parallel with.

The PO disconnected the key chime. So you just disconnected the orange/white from the chime and connected it to the positive of the voltmeter? Where is the chime located?

[focodave]

Yes.
It is located under your glove box on a plate that also has the dual relay mounted on it.

[spider2081]

Voltmeters are very, very high-impedance, low current draw devices -- so they don't need to be fused -- and -- they don't affect anything they are wired in parallel with.

I don't agree with this comment.
The purpose of a fuse in a circuit are to protect the power source not not the load. A fuse in a car protects the car against an electrical fire. A fuse (circuit breaker ) in a home protects the house not the appliance. Any wire connected to the power source should be protected by a fuse or circuit breaker. The size or value of the protective device is determined by the wire size used. The fuse should blow before the wire burns, even if the wire is inadvertently shorted directly to ground. The wire size is determined by the current draw of the load and length of wire needed. In this case a voltmeter is indeed high resistance and therefore draws a small amount of current. This means the wire diameter for the voltmeter could be small in diameter. If the wire were to inadvertently short to ground it will burn and could destroy the car if it is not properly fused.
Older cars like our Fiats have un-fused circuits. Most of these circuits use # 12 wire or larger. Still not the safest design. Given the choice I woulld not install the voltmeter without fusing the votage source wire.

[davery]

Voltmeters are very, very high-impedance, low current draw devices -- so they don't need to be fused -- and -- they don't affect anything they are wired in parallel with.

I don't agree with this comment.
The purpose of a fuse in a circuit are to protect the power source not not the load. A fuse in a car protects the car against an electrical fire. A fuse (circuit breaker ) in a home protects the house not the appliance. Any wire connected to the power source should be protected by a fuse or circuit breaker. The size or value of the protective device is determined by the wire size used. The fuse should blow before the wire burns, even if the wire is inadvertently shorted directly to ground. The wire size is determined by the current draw of the load and length of wire needed. In this case a voltmeter is indeed high resistance and therefore draws a small amount of current. This means the wire diameter for the voltmeter could be small in diameter. If the wire were to inadvertently short to ground it will burn and could destroy the car if it is not properly fused.
Older cars like our Fiats have un-fused circuits. Most of these circuits use # 12 wire or larger. Still not the safest design. Given the choice I woulld not install the voltmeter without fusing the votage source wire.

I understand your concern. If the voltmeter is connected to the key chime which is connected to the ignition, wouldn't it be fused since the ignition is fused?

[focodave]

Don,

Yes, the chime circuit is fused.
And spider2081 is correct -- for ultimate safety, you should fuse everything that you add for good measure.

Dave

[mpollock]

My preference would be to connect the volt meter directly to the battery through a small (maybe 1/4 amp) inline fuse placed close to the battery. The wire size could be selected by whatever will give you sufficient mechanical strength since the current through the wire will be very small. For me the most practical use for a voltmeter in a car is to monitor the voltage of the battery - to monitor the charge state of the battery if the car is not running, and to monitor the charge/discharge status when the car IS running. Since the resistance of the wires is non-zero, there will be a voltage drop through the wire the meter is connected to. The voltage drop depends on the length and size of the wire and what it's feeding. For low-current circuits such as the chime circuit the voltage drop will be fairly low - maybe a few milliamps. For high current circuits such as headlights or starter the voltage drop will be several volts. If you run the volt meter lead directly to the battery and don't run anything else off of that circuit the voltage drop will be constant (won't vary due to changing loads) and will be in the single digit millivolts, and therefore negligible.

[davery]

My preference would be to connect the volt meter directly to the battery through a small (maybe 1/4 amp) inline fuse placed close to the battery. The wire size could be selected by whatever will give you sufficient mechanical strength since the current through the wire will be very small. For me the most practical use for a voltmeter in a car is to monitor the voltage of the battery - to monitor the charge state of the battery if the car is not running, and to monitor the charge/discharge status when the car IS running. Since the resistance of the wires is non-zero, there will be a voltage drop through the wire the meter is connected to. The voltage drop depends on the length and size of the wire and what it's feeding. For low-current circuits such as the chime circuit the voltage drop will be fairly low - maybe a few milliamps. For high current circuits such as headlights or starter the voltage drop will be several volts. If you run the volt meter lead directly to the battery and don't run anything else off of that circuit the voltage drop will be constant (won't vary due to changing loads) and will be in the single digit millivolts, and therefore negligible.

So if I was to do this, what size wire would you recommend for the pos going directly to the battery? Right now I have the voltmeter running through the chime connection and is reading 11, which I assume because it hasn't been driven in a few months.

[bluespider262]

You typically want your voltage gauge at the point of largest potential drop vs. the battery, if possible, but that isn't always practical vs. the effort.

You definitely don't want it on the battery directly (unless you run it through a relay off the ignition switch.) It will create enough drain on your battery to be an issue.

For ease of installation, I would probably use the "Run" terminal off the ignition switch or one of the wires directly off of it.

Best spot would probably be fuel pump b+ or something else in/near the trunk area that is on switched power. A circuit in the rear of the car would almost definitely have the highest potential drop in the system because it has to travel from rear to front (at least on a model w/ battery in the trunk) then front to rear again via small gauge wires. You could lose possibly up to a volt maybe more depending on condition of wiring/connectors.

[davery]

You typically want your voltage gauge at the point of largest potential drop vs. the battery, if possible, but that isn't always practical vs. the effort.

You definitely don't want it on the battery directly (unless you run it through a relay off the ignition switch.) It will create enough drain on your battery to be an issue.

For ease of installation, I would probably use the "Run" terminal off the ignition switch or one of the wires directly off of it.

Best spot would probably be fuel pump b+ or something else in/near the trunk area that is on switched power. A circuit in the rear of the car would almost definitely have the highest potential drop in the system because it has to travel from rear to front (at least on a model w/ battery in the trunk) then front to rear again via small gauge wires. You could lose possibly up to a volt maybe more depending on condition of wiring/connectors.

Do you know what color wire comes for the "run" switch? Looks like my ignition has a lt blue/black, brown, red, black and pink.

[RRoller123]

[bluespider262]

Pink is optimal as far as something under the dash. At the "top" of the connector pictured (i.e. add it to the 2 wires already on that pin if possible) or further up somewhere. Do NOT use one of those junky "wire taps" - either add it to an existing connector by removing the terminal and soldering it onto it, or physically splice into the pink wire somewhere convenient and then solder/shrink wrap that tap.

If you are grabbing pink under the dash it is already fused via the brown wire so not sure I'd bother with another fuse in series.

Another option is to pull it off the coil. You won't have to cut/splice anything then. Keep in mind if you grab it at the coil and run it back into the cab I would put a fuse as close to the coil as possible. You don't want a run that long + exposed unfused from where it starts. That way if you accidentally cut the wire or insulation rubs off and it shorts, you won't have a length of live wire before the fuse under the hood or dash. This is probably the way I'd go assuming I had an existing hole in the firewall to run it through. Make sure you run plastic split loom on that wire for extra safety against abrasion too. Should look very clean.