fusing a voltmeter?

[1990LTD]

I want to tap 12v for my voltmeter right from the alternator. Well, not right from it, but after the megafuse, where it runs to the battery...the + battery cable I picked up has another little 12ga coming off of it in addition to the big honkin' 4ga cable, and I want to get an accurate reading of what my charging system is doing.

this is what i've got;




The volt meter is the only thing I'm going to run off of that 12ga wire...should I put a fuse in there? I don't imagine the thing is going to try to draw too many amps.

[gadget73]

I wouldn't run a voltmeter right off the battery. The battery will go dead eventually even from the tiny draw of the meter, and honestly metering the power available at the fusebox is more useful since basically everything feeds out of there. If you do want to do this, then absolutely put a fuse in there. I'd probably use a 1 amp and put it as close to the battery as possible. You'd be perfectly safe feeding the voltmeter with 16 or 18 ga wire. It pulls no appreciable amount of current.

[1990LTD]

It didn't even occur to me that putting it there would basically run it off of the battery when the alternator is not doing anything

[86VickyLX]

I tapped mine through the circuit breaker of the wiper motor. On the fused side (if anything happens to the circuit the circuit breaker will open)... It's pretty accurate as to what voltage is coming into the car.

[87gtVIC]

I have mine right out of the fuse box...alternator is connected to fuse box...fat jumper from fuse box to starter solenoid...then fat fat cable from battery to starter solenoid...fuse box in my case is getting all the juice and distributing it so that is where I wanted my voltmeter to monitor whats going on. I am using a 15amp fuse...because I had no idea a year a go what to use.

And there is a way to connected the voltmeter properly....by properly I mean monitor your system only when the car is on or key is in place.

Simple really..my dad and I both have it set up this way because having a voltmeter run continuously is pointless in my mind.

You need a relay....85-86---coil....give 86 keyed power and give 85 ground. give 30 ground and connect the ground of the volt meter to 87a. run the volt meter power lead to wherever you want to monitor the power from.

This way it will only read volts when the key is on, or the car running.

Also you get a more accurate reading of the voltage when you are getting it from a main distribution point such as solenoid..or a fuse box because everyone is drawing power from there....guess what happens when you use your wiper motors in the above case....the volt meter will be severely freaking out because it is monitoring power that is directly used through the wiper motor...then the common distribution point. You will still get voltage reading but it would be annoying to witness while the wipers are one.

[GM_Guy]

For a voltmeter, tapping into the radio power wire will do just nicely.

Alex.

[1990LTD]

Radio power it is.


I was silly when I installed the voltmeter, I combined the 12v for the gauge and the 12v for the illumination and tapped the headlight circuit so it only comes on with the lights....but the gauge is reading the power that the headlight switch is getting, which changes when the headlights are on, brakes, etc...basically anything that changes the brightness of these old shitty headlights thanks to the wiring. The readings I get from the voltmeter are way screwy because I'm getting better than 14v off of the battery when the car is running and I never see better than 13 on the meter.

For simplicity sake, I will tap some other random key-on power from the fuse box and keep the gauge illumination on the headlight circuit. Headlight relays are obviously coming soon, too.

[GM_Guy]

Once you relay your lights you'll probably see voltmeter readings more in line with what is at the battery. Now you know why relay upgrades are so popular.
Also go over your battery and starter relay connections make sure everything is clean and tight, and you will likely see an improovement in your voltmeter readings as well.
See, the things already doing its job by giving you a heads up to potential weak points. (note the term used is potential, not definate.).

Alex.

[1990LTD]

Needs a new fender solenoid and + battery terminal, as I've discovered

[87gtVIC]

I still like the way I have it. When first installed...dad installed it first back when I got the car...he just tapped into some keyed source and it was just too jumpy for my liking. The way I have it now is neato because it does not jump near as much as it did when it was tapped into someone else's power.