General Third brake light issues.

[BambOObeast]

Hi all, I hope someone can help me with the issues I've got with my 2006 punto,
Firstly on start up, the Amber warning triangle comes on with the warning message "check lights".. On checking lights, third brake light found not working, bulbs found blown, bulbs replaced, light still not working, wiring traced and broken wire found where loom from light unit comes out of rear door into side bodywork ( through a rubber corrugated tube). Broken wire fixed, light still not working, checked voltage at light unit plug and voltage found to be fluctuating between 5 & 7 volts with the ignition on, but without the brake pedal being pressed, same fluctuations of voltage when the brake pedal is pressed...
I thought there should be zero voltage when pedal is not pressed and 12 volts when pedal is pressed. Anyone got any ideas how to fix this fault..

Any help would be appreciated.

 

[BambOObeast]

Just a quick update, if anyone's interested, I found a broken postive wire, in the bodywork to rear door grommet, caused by the plastic tube for the rear window washer, being broken in two, leaving a sharp edge which cut through the wire. Repaired wire, and after a bit of wire wriggling
Found the connectors worn in the plug that pushes into the third light unit, connectors tightened , and now working fine, still no idea where the fluctuating 5 to 7 volts came from.

 

[DGPunto]

That's a classic problem that is worth checking whenever you have a problem in the tailgate. Did you check the washer hose while you were in there? That can go hard and break too which let's water leak inside the tailgate

 

[BambOObeast]

The washer hose is the plastic tube that split, and cut the wire to the third brake light...
Any idea why I was getting fluctuating voltage at the brake connector plug when the brakes were not pressed.. is it something to do with the monitoring of the bulbs, because now I've repaired the wiring and got the third brake light to work, the Amber warning no longer is lit...