Volt gauge disparity

[Spargewort]

Hello, my name's Bob and I am a 65 year old Oregonian. First post!

I work on my 90 K1500, my daughter's 93 K1500, my son's 2005 Burb, and my 99 Tahoe..

I recently bought an XTool D7 and have been looking at live data on the 99 Tahoe.

I notice Ignition voltage reads 13.5 on the scanner, yet the voltmeter in the cluster shows over 14 volts.

I wonder where in the truck the voltmeter receives its signal, and if it the same sensor the scanner is reading?

Cheers, Bob S.

 

[Eman85]

You're 65, bet you can't do what you did when you were 20. That dash volt indicator is 25, bet it can't do what it did when it was new. Between dust and wear and the fact that it's a mass produced indicator be grateful it still indicates.
The dash gauges receive voltage through the fuse panel, no sensor but many connections along the way including a plastic printed circuit. PCM receives it's voltage also through fuse panel and has connections along the way. If you want true voltage for troubleshooting go to the battery and the back of the alternator.

 

[Spargewort]

Haha, good point! However, there are some things I do better with age... and the gauge is in agreement with the multimeter reading at the charging cable, 14.2 volts.

The scanner gives 13.5 so maybe that is accounting for some resistance in the pcm signal path?

And perhaps charging voltage 14.2 is going to the circuit board of the cluster and gets resistance for all the gauges except the voltmeter?

I appreciate your thoughts.

Bob