Rev counter flickers

[MarcoPau]

Hi, I assume I have a few electrical problems back there behind the cockpit: the rev counter will go up when hitting the brake or when using the indicators, it'll flicker together with the blinking, on and off, up (to 5.000 revs or so) and back down to the actual revving. I also noticed I have a few other electrical problems: the car radio will tend to turn on by itself when starting up the car and when hitting the throttle, plus both my odometer and trip meter are not working any more. I also see the head lights lowering their intensity when the engine is revving low, such as when I change gear.

Do you have any hint?

Thanks a lot!

[steely]

see if you can buy a small voltage meter for the cigarette lighter and use it as a monitor.
I forget the optimum voltage level, but 13-14 should be ok - look for unusual levels.
Maybe check your battery levels.
Check your grounds, make sure they're clean/tight - including the braid to the transmission.
It's all I can think of - this will eliminate some things as well as maybe pin point a possible voltage regulator problem.

[MarcoPau]

Well I think I could use any multimeter for that purpose. Do you think a low battery could cause this?

"Braid to the transmission" is the wires going from the speedometer to the gearbox?

Thanks for now

[Joe Bob]

Wonky tachs usually mean the alternator is on its way out.