Ground Issue? Gauges with loose movement

[Bow TieTill I Die]

Just recently purchased my 92 Gmc C2500, I’ve noticed now that the gauges have a lose movement to them, and they are constantly changing. My RPM and Spedometer gauges seem to be working fine, but the temperature gauge one moment will be in the centre where it’s suppose to be while running then dip down, or up out of no where. I never know how much gas I have because the fuel gauge will tell me different readings every few minutes. The oil pressure gauge has the same speratic movement. the parking break light will also come on and stay on after about 5 mins of driving. Now I just purchased a new battery when I got the vehicle and from the looks of it the alternator was changed recently, the old one was in the back, when I bought it lol. When the truck is running idle with nothing on I’m sitting just under 14 volts according to the gauge reading, when i turn on the heater or any of the other accessories it will dip down more and more, I don’t think this is normal it should sit at 14 constantly right ? I’m just looking for suggestions on what could be wrong? 

 

Thanks.

[Bow TieTill I Die]

 

[Logan Lanfear]

Everything seems to be fine from that video.   Oil pressure is fluctuating a little but I think the more common problem with these gauges is the sender off the engine.  As for alternator load it also seems okay.  But you can easily test that with a multi meter.  Anything right around 14 is good.