New HU, pulsing on/off every 20 secs. what's wrong?

[Cyaegha]

I installed a new HU for my VZ using the cable harness the guy who supplied it made. First off it would not retain settings and would not switch back on when I switch accessories back on. The guy told me to switch the constant and the ignition wires. This got it to retain settings, but now it seems to pulse every 20 seconds when the power is off.

I can hear a click under the dash, the unit pulses on/off and the antenna goes up a bit then back down.

Does anyone have any ideas what's going on?

[Adelaideprosound]

You either dont have a good earth, or a good connection in those wires you swapped around.

[azzfox]

bad head unit earth. if the head unit isnt grounded directly to chassis then do so! for some reason some head units dont like the factory earth loom. has happened to me before.