New temp gauge playing up, "help please"

[si tate]

Well the temperature reading is spot on but the issue i have is with the built in volt metre. With ignition lights on it reads 12.5ish volts & once runniing it reads 13.4 - 13.9ish, now the problem comes when you rev the engine or drive "at any speed" the voltage drops to around 9.0 volts & stays there unless i turn the head lights on + full beam then it goes up again but drops off after a few seconds.

WTF is going on, ive checked & double checked the wiring is correct so can anyone shed any light on this please, hoping its something simple but knowing my luck...........

Cheers si.

[BUSHWHACKER]

Has it got a good earth? i.e fixed to bare metal not just scratched paint.

[si tate]

Has it got a good earth? i.e fixed to bare metal not just scratched paint.

Ive put it to the battery earth so im assuming its fine but will sand it all in the morning just to be sure, ive had the volt metre on both the live & ignition live & they both read 12.6/8 volts so the correct voltage is getting to the gauge & even when it drops to 9 volts both the lives still show 12/13 volts so could a bad earth cause this?

[Albannach]

Any bad connection will do that.

[BUSHWHACKER]

As it's a digital gauge, it's probably just over sensitive.
If the battery voltage did actually drop to 9v when driving, the fuel pump would probably complain and the truck would splutter.

Alternator belts OK?

[si tate]

As it's a digital gauge, it's probably just over sensitive.
If the battery voltage did actually drop to 9v when driving, the fuel pump would probably complain and the truck would splutter.

Alternator belts OK?

Everything checks out ok, tested battery & kicking out 14 volts+ when revved but gauge still showing 9volts. Im not overly fussed for the battery metre but it would be nice to have it working properly.
Cheers.

[BUSHWHACKER]

Everything checks out ok, tested battery & kicking out 14 volts+ when revved but gauge showing 9volts. Im not overly fussed for the battery metre but it would be nice to have it working properly.
Cheers.

Send it back, you've got a duff one.

[si tate]

Send it back, you've got a duff one.

Was thinking that, i'll do the earth in the morning & take it from there.