Zafira tail/brake light issue

[rsgaz]

Would that imply that the 13v reading shows the pulse width modulating wasn't working

It would imply that the brake pedal was pressed, giving it the full voltage(non modulated), but multimeters that aren't specifically designed to read PWM voltages will give spurious readings.

OP, have you tried just disconnecting the battery for 30 mins, to reset all the systems and see what happens?

ive checked all the 5amp in the rear box

Have you checked for loose plugs in that rear box? I take it it's one of these?

 

[Gasescape]

OP, does the holder look like this?...

View attachment 121591

Yup that's the one
Okay tested good side 3.6v
Good side brake pressed 8v
Faulty side just measure 13v with or without brake .
Good continuity on supply & gave additional earth to still Same

Tried with a test lamp good side's good. Bad side does fook all

 

[Gasescape]

Haven't done anything with battery !
Is it worth a try ?
Not got oscilloscope

 

[Gasescape]

Had the plug (green one) disconnected & it looks fine , no corrosion or water ingress.
Is the rear control box prone to faults ?

 

[rsgaz]

Haven't done anything with battery !
Is it worth a try ?

Pull out all the plugs from that rear box for thirty mins, it'll kill two birds.
That'll reset the box which does the modulating and you can check all the plugs are fully pushed home when you put it back together.

 

[rsgaz]

Is the rear control box prone to faults ?

I'm not a Vauxhall expert by any means, so I don't know, but seeing as it's that box doing the modulating, it's a prime suspect.

 

[Gasescape]

Wee update on this
Was a fault with the rear control box ,
Vauxhall mechanic has managed to get it working with a little trickery
Car will be traded in if I ever need to spend big bucks on it ...

 

[John1979]

I had a problem with my tail light not working on my zafira b 2007 I checked all the wires from the back end still no sign then I decided to check the foot pedal switch to find 3 wire going to it one of the wires was lose so I jiggled it back into place now I have all 3 brake lights working together once more