New Voltmeter - stock meter wonky

[dieseldaver]

My in-dash voltmeter reads all over the place, and is usually in the red on the dash, despite reading 14.7 Volts at the alternator. I have checked grounds (yep, all of them), done the new battery terminal connections, and even put in new grounds to the dash, but I still get some weird electrical gremlins happening. Like my speedo revving up when I'm in Park and revving up the engine. Anyways, what I'm thinking of doing is hooking up a good, old fashioned voltmeter in the cab. Any suggestions on where to make the connections? Do I hook it up at the batteries? The alternator? Somewhere inside the cab?

[goodmonkey]

Try hooking it up to a switched source, as the original is hook through the GAUGES fuse. If you where to hook it up straight to the battery, you'd get a reading all the time, placing a constant drain on the battery. While this drain would be nominal, still probably a good idea to switch it. Wish I could give you more answers on the cluster though. If there was a voltage regulator on the cluster then I'd say it was heading south, but looking at my schematics I can't see one.

[ChevyDooley]

On mine I pulled the speedo cluster out. On the back you'll find some interesting plastic "circuit board" wannabe dealy. You'll also see little metal prongs sticking thru that attach the gauges to the plastic "circuit board". Bend these back hard against the plastic and clean any contacts you find with a official use electronic cleaner. Ya know the kind that removes even paint!? Yeah this fixed all my problems after chasing nothing for weeks!

[tom.mcinerney]

Haven't had experience personally, but 'speedo revving in park' is classic sign alternator problem these trucks, from reading here.

[john8662]

Just a note, the reving up the engine and the speedometer slowly rising isn't uncommon. The last two trucks I have had that were electronic speedo's did it, My 95 6.5 suburban does it to.. I like the idea about the connections on the wannabe circuit board ont the back of the instrument cluster being the problem, definitly check that out for the voltmeter.

[dieseldaver]

I had the dash out a while back when I was trying to track this down, and cleaned up those little contacts, but just with a small file, not that cleaner stuff (didn't have any handy). Any brands you'd recommend for a good cleaner?

If this doesn't work, I'd still like to put a new gauge in, and would like it to be switched. Anybody have a suggestion as to where that connection can be made?

[tom.mcinerney]

Dave, probably not what you want to hear, but can't resist: Usually oil pressure gages are installed at the 'end of the line', furthest from oil pump; this gives a pessimistic, 'conservative' readout.
The OEM instrument panel voltage gage is similar in its installation, but maybe not a great place to tap voltage because it can give a false bad reading when everything except the instruments have good power. One way to look at it is if you all ready have one pessimistic reading, wire the extra volt gage to something near the alternator's attachment to battery. You could also tap into a sensitive circuit(FSD power feed).
I've just installed aftermarket gauge in dash. I decided to use a switch[on-off-on] to switch the meter's connections between two input points. I haven't yet decided where, but will probably be two of following three places...1,alternator 2,fuel heater circuit(switched) 3,FSD feed(switched, i think). The fuel heater circuit is nice since it's in middle of engine controls and will have a significant(100W) load which turns off and on. Power to the fuel filter's water sensor circuit might read more stable, since the load is only milliamps. 'Hope this helped'.