Wiring help when replacing voltage meter

[bobby1253]

I am replacing an old analog voltage meter with a new digital meter. The old meter has metal tabs for the +, - and C wires. The installer ran wires to the meter and attached slide-on clips to connect to the metal tabs on the meter. See photo below.

The new digital meter has a red and black wire. See photo below.

How would you recommend I make the connection of the red and black wires to the existing in-dash wires with the slotted tab connectors? I want to keep this simple, but safe.

Secondly, is it recommended to have the digital meter connected as "always on", or have it come on only when the key switch is on?

[bobby1253]

Update: Got the new meter installed successfully. All is working great. Thanks to those who helped me on and offline. I really appreciate it!

[RNajarian]

Originally Posted by bobby1253

Update: Got the new meter installed successfully. All is working great. Thanks to those who helped me on and offline. I really appreciate it!

Any wisdom for those of us about to do the same project?

[HeatWave]

Originally Posted by bobby1253

Update: Got the new meter installed successfully. All is working great. Thanks to those who helped me on and offline. I really appreciate it!

Did you wire the new meter "always on" or
"with the key switch"?

I'm going to install the same meter soon.

[Mooncarter]

Tell us what you did and how so everyone can learn.

[bobby1253]

I am a beginner so I did a lot of research before I got started. I previously had someone install a voltage meter which never worked right. It was the kind that had a sliding scale from left to right that was supposed to gradually move from 100% to 0% as the battery voltage dropped. It was crap. Following some great recommendations here, I purchased a digital voltage meter from ScottyB at cartsunlimited.net and watched a lot of YouTube videos to figure out what I needed to do. The previous installer had already cut a hole in the dash and I was able to use the same hole for the new meter. I removed the 3 screws (Torx T30 and T15) to get inside the dash. The old meter had three male spade connections, +, -, and "C". The guy who installed that first meter wired it to the key switch. I unplugged the 3 female spade connectors and used a multimeter to figure out which wires had current. With the key switch off, the + (red) wire showed 50.3v, and the "C" wire showed 0.0v. Once I turned the switch on, the "C" wire showed 50.3v. Whereas the old meter had 3 spade connections, the new meter from cartsunlimited.net only had a red and black wire. I decided I wanted the meter to only be "on" when the key switch was on. So I ignored the existing red wire spade connector from the old meter and instead connected the red wire from the new meter to the existing "C" wire from the first install, and of course, the black wire to the - spade connector from the first install. I used a crimping tool to attach male spade connectors to the new black and red wires so I could simply plug the new meter into the existing female spade connectors from the original install. Everything works beautifully.

I have noticed that the voltage reading off the key switch is slightly below the voltage I would get if the meter was wired directly to the battery pack. We're talking maybe 0.2 or 0.3 volts difference. For example, if the voltage directly off the pack is 50.6v, I might be getting 50.3v or 50.4v from the key switch. I can live with that. And it means I won't have to run new wires from the dash to the battery pack just to pick up that little improvement in accuracy. But that is of course personal preference.

[Sergio]

For future reference on those 3 wire meters.

The "+" goes to pack positive or key switch "always ON side".

The "-" goes to pack negative.

The "C" wire is used to turn the display ON/OFF and can be wired to either the "switched side" of the key switch (my preference) or the "always ON" side of the key switch depending on preference.

[yawood]

Originally Posted by bobby1253

I am a beginner so I did a lot of research before I got started. I previously had someone install a voltage meter which never worked right. It was the kind that had a sliding scale from left to right that was supposed to gradually move from 100% to 0% as the battery voltage dropped. It was crap. Following some great recommendations here, I purchased a digital voltage meter from ScottyB at cartsunlimited.net and watched a lot of YouTube videos to figure out what I needed to do. The previous installer had already cut a hole in the dash and I was able to use the same hole for the new meter. I removed the 3 screws (Torx T30 and T15) to get inside the dash. The old meter had three male spade connections, +, -, and "C". The guy who installed that first meter wired it to the key switch. I unplugged the 3 female spade connectors and used a multimeter to figure out which wires had current. With the key switch off, the + (red) wire showed 50.3v, and the "C" wire showed 0.0v. Once I turned the switch on, the "C" wire showed 50.3v. Whereas the old meter had 3 spade connections, the new meter from cartsunlimited.net only had a red and black wire. I decided I wanted the meter to only be "on" when the key switch was on. So I ignored the existing red wire spade connector from the old meter and instead connected the red wire from the new meter to the existing "C" wire from the first install, and of course, the black wire to the - spade connector from the first install. I used a crimping tool to attach male spade connectors to the new black and red wires so I could simply plug the new meter into the existing female spade connectors from the original install. Everything works beautifully.

I have noticed that the voltage reading off the key switch is slightly below the voltage I would get if the meter was wired directly to the battery pack. We're talking maybe 0.2 or 0.3 volts difference. For example, if the voltage directly off the pack is 50.6v, I might be getting 50.3v or 50.4v from the key switch. I can live with that. And it means I won't have to run new wires from the dash to the battery pack just to pick up that little improvement in accuracy. But that is of course personal preference.

Excellent. I hope you also wrapped the old red terminal with electrical tape or otherwise insulated it so it can't touch anything and cause a short.

[RNajarian]

Thanks.

I was considering going off the key switch for the “+” lead. Didn’t realize there was a slight voltage difference.

I’m referencing my wiring diagram to see if there is a hot lead somewhere I can tap into. I rather not run a wire the length of my cart.

[Sergio]

The difference in voltage is most likely related to the meter accuracy and You can easily verify that by temporarily connecting the meter directly to the batteries in the compartment using short wires.

Take a note of the voltage and then connect the meter to the key switch to see if the voltage is different.

When I was playing with my OBC in order to provide temperature adjustment for winter charging, I also noticed that the difference in voltage was not linear, there was about a 0.2v difference between the reading error when the pack was 48v vs when the pack was at 62v.

In either case the dash meter was reading less voltage so that is a good thing since my pack was actually 0.2v higher than the meter was reading.