Adding a Voltmeter

[7783911]

I have had a few issues over the years with Battery charging and finally replaced the battery...but being somewhat paranoid/anal,

I checked for parasitic leaks and found none..so far so good
I tested at the battery and voltage is good (engine off)
I started the car and at an idle of 850 I dont show any increase in voltage across the terminal, but if i increase engine revs (say 2K) I do see in increase in voltage indicating charging?

My question is twofold

1 should charging being occurring at idle and if so, then what would i test next to determine why i am not getting charging at idle. How do i test output at the alternator (belt is nice and tight so thats not a culprit). Pictures of how to test at alternator greatly appreciated!

2 I would like to install this voltemeter/USB combination in my central console




what are the best wires to use or should I just run new wires direct from Battey Posts>


Thanks for your help

[zedsn]

If I remember correctly the alternator has to be over 1500 to start charging. I ran a volt gauge and ran it from the radio + (yellow) wire that was on all the time to keep my preset stations and worked fine like that during my ownership of the car.

[Jack Stands]

I took the easy way out and simply plug this into the cigarette lighter when I want to check.

[bkreigsr]

[7783911]

I looked at the cig outlet option but decided i liked using the console area better and wanted the usb option too...thanks

Bkreigsr: What did you use for power supply..i was hoping to avoid messing with ignition switch supply but if i did use that, can anyone indicate which is the best wire to tap into? (color/position)

[bkreigsr]

Not the easiest way to wire a gauge, but I snaked a hotwire to the fuse panel, and the ground to the common stud in the trunk under the cowling.
An easier place to draw a reading from would have been the ignition switch, but some ham-fisted stereo 'technicians' made that alternative less attractive. (whole other story)

I liked this gauge because it is self-lit.

Bill K

[dad911]

I prefer an analog-looking gauge bill. Got a link to that one?

[7783911]

if you have a link to a good analogue please share..i am not set in my ways

[metalracer]

Originally Posted by dad911

I prefer an analog-looking gauge bill. Got a link to that one?

https://www.egauges.com/VDO-Gauges-s/20001.htm

[Lake Guy]

I installed AEM analogue gauges after I ditched the AC switches. Power is from fuse panel and signal on/off is from radio feed. Disregard the plastic packaging that was on during fit up when the photo was taken

[James Brown]

i sent my gage to Palo Alto speedometer and they replaced the useless oil quanty gage with a voltmeter, looks factory. Easy peasy

[fanaudical]

I installed two gauges (one dual-channel CHT and one voltmeter) from Westach in a two-gauge panel in place of my ashtray. Voltmeter runs to switched power on the fuse panel.

My '75 with external voltage regulator doesn't appear to charge until ~1400 RPM. I don't worry about it too much; I've got a big battery and my 911 doesn't spend a lot of time at idle...

[RNajarian]

In order to keep the look of my dash period correct this is what I added . . . Original VDO Voltmeter and VDO external temperature gauge. I was able to wire into the glovebox an extra cigarette lighter that I have put a USB plug into.

So I have the option of USB power whenever I need it.

[911pcars]

You can connect an accessory voltmeter to any part of the electrical system that's powered by the main 12V storage battery. However, you may wish to connect to a circuit that's only active with the ignition ON. There are several (typically, radio, cig. lighter, wiper, etc. Use a voltmeter or test light and probe the fuse box for those circuits. The fuse box source would be a good idea to fuse-protect the voltmeter source wire.

Sherwood

[bkreigsr]

Sorry - I'm not holding out info.
I bought the gauge in 2005 from Summit Racing.
It's a Stewart-Warner and it's only 1.5 inch diameter.
It took Summit 5 months to complete the order, as SW had discontinued this series.
( I used to be a very patient person)

I think Auto Meter might be producing a 1.5" version now.

Bill K

[famoroso]

From an existing thread. Integrating the voltmeter into the tach, a la 930 factory boost gauge, makes me happy... DANGER! install volt meter now!!

[clarkd]

Here is my "radio delete" volt meter. It is not switched so it is on all the time. I use it to see when it is time to charge my battery. It was advertised as a marine application. USB, volt meter and cig lighter. I think I bought it on Amazon. Car is a 73. I slid the face plate in the channels with the glove box open. Tapped aluminum backing pieces. Has 3 inline fuses.

[7783911]

Ok,,,,,one more dumb question...

I don’t want to run from ignition switch..so what is the best fuse to run a new wire from (77 targa)
I assume I run from bottom of fuse which is output side?
Do I need to bump up fuse rating?


Thanks,,,VDO gauge is being delivered soon and I plan to build a new center console to add gauge as well as a couple of custom storage options..like a cup holder or CD slot

Tx

[bkreigsr]

Buy a test probe for four bucks to see which fuses are live when you switch the ignition on.
No need to upgrade the fuse - the volt meter draws zero volts - just reports it. The bulb draw is negligible.
Bill K

[T77911S]

fuse sizes are based on wire size.
wire size is based on load or current that the load will pull.
if you bump up the fuse size your wires will melt and start a fire before the fuse blows.

run it from the bottom, you want the wiring to the meter fuse protected also.

best thing is to goto a parts store and let them test the charging system and battery, its usually free.

850 is a little low. 950 is a little better.
make sure the alt light works and is out when the engine is running.
check your battery terminals for heat. that can be a sign of bad connections.
make sure the ground strap from the alt to the block is clean and connected. same with other major power connections. ground strap from tranny to body, ground from battery to body. clean all these.
measure voltage at battery with it running, should be above 13v.
turn on some accessories like headlights and radio. check volts.


are you still having issues with it as far as it wont start after sitting.
if you are driving the car daily or every few days and it always starts, you are fine. if you have a charging issue the battery WILL eventually go dead.