Voltmeter wiring question

Gunter · Gunter's Garage

I have a Voltmeter and am thinking of installing but want to hear how the experts would do it. Where would you wire/tie in this meter? Thanks.

Kroggers · Kroggers's Garage

I am about to do the same job, and plan to connect one end to the switched live (connected to my stereo), and the other end to the earth block under the dashboard. then I will wire the light of the light cable again going to my stereo - As long as the stereo in your car is wired up completely and correct, then you should be able to get all the connections you need directly from there.

Gunter · Gunter's Garage

Hmmm. I have to think about that, it sounds too easy.

Kroggers · Kroggers's Garage

OK, I will let you know how I get on when I have done it. but all you want the meter to do is measure the voltage between the + and - on your battery when the car is running (therefore take the connection of the switched power and not permanent power).

Kroggers · Kroggers's Garage

OK, just won the bid on ebay for my battery volt gauge, so as soon as it arrives I will fit it and let you know how I did it (and more importantly, if it works), but with my electronics qualifications, I am confident in my approach...

randywebb · 04-07-2005, 10:35 AM

You have to decide where you want to measure the voltage...

It will not be exactly the same in all circuits at all times.

1. a big load (starter) can pull the voltage down in its own or other circuits while it is running -- blower fans would be next in line

2. resistances will drop the voltage at vaious places -- mostly at corroded grounding points, but perhaps also where the wire itself is pinched, corroded, too small in dia., and etc.

So, draw a map in your mind of all the circuits with nodes for all the grounds...

Mysterytrain · 04-07-2005, 10:35 AM

I installed my voltmeter in the center console of my 78 under the A/C switches. I took the 12 volts from the blower switch and ran the ground to the chassis. I forget what color the hot wire is but is can be found in the wiring diagram. The only bugger was the internal light on the voltmeter. You can tie it to the 12 v and have it on all the time or put on the same circuit as the dash lights..low and behold I was able to tap into the Black heater lever defrost light fixture on the floor between the seats. Slight pain to do but a nice clean install. No wires hanging from the dash. Did it while I had everything pulled apart for the footwell blower installation. I will try to post a pic of my console but for now here is the defrost light fixture:

JTL · JTL's Garage

I wired the + directly to a switched terminal on the fuseblock. The - is wired to the aftermarket amplifier ground under the passenger seat. The voltmeter backlight wiring is tied into the gauge lights for dimmer control.

jt
-84 targa

911pcars · 04-07-2005, 03:43 PM

You can connect the + wire of the voltmeter to any 12 volt source wire. Close to the fuse box is fine, but source voltage is the same throughout the vehicle (for voltage gauge purposes). However, you will probably want to connect to a switched circuit, otherwise the gauge will display voltage constantly. Any circuit controlled or activated by the ignition switch should be fine.

Sherwood

911pcars · 07-04-2006, 11:32 PM

Don't know how much power it consumes, but if you connect directly to the battery terminals, the gauge will be active 24/7 (with bulb ON?). Better to connect to a circuit that is only active with the ignition ON.

Sherwood

rnln · 11:49 PM

good idea.
I thought about it right after I clicked submit therefore I deleted the question, again, before I saw your response.

Now I am thinking of another thing. What rate of fuse (amp) should I use inline of the (+) wire? I was supprise that someone posted that all in dash components are no fuse protection at all.

Thanks.

Early_S_Man · 07-05-2006, 05:55 AM

The meter isn't going to use more than an mA or two, so assuming an inline blade-type fuse, get a Black 1 Amp or Gray 2 Amp fuse.

rnln · 07-05-2006, 11:14 PM

Thanks.
Hard to remember all these. Let see.. headlight 3 amps, voltage gauge 2 amps.

911pcars · 07-06-2006, 12:52 AM

Connect the VM to any convenient, ignition-activated position in the fuse box. However, excessive resistance in this circuit (e.g. poor fuse connections) will show up on the VM as reduced system voltage, so make sure all connections are good. To avoid this, I recommend connecting to an existing circuit with relatively short circuit wiring.

VMs have a relatively high internal resistance, so current level (amps) is usuallly very low.

Sherwood