Rear Fog light has made an mot fail

[Wildrobot]

hello so my rear fog light on my Mazda bongo has fail the mot due to not working.

The bulb is fine, I used a multimeter to find out it wasn't receiving power.

So I've rigged up a wire from the switch to the bulb socket but the bulb still doesn't light up.

I've now completely removed the bulb socket and tested it on the battery which lit up the bulb. Reconnecting my new wire and then either earthing the bulb socket or touching the negative on The battery doesn't work.

The new power wire is reviving volts, and the light on the switch lights up when the connection is complete it's just the bulb doesn't light up, I've tried different bulbs and get nothing

Is there anything else I should be checking I'm a total novice, relays? Amps?

Any help is muchly appreciated

 

[telectrix]

measure resisitance between the lamps earth and the metalwork of the chassis. if below 1 ohm, then trace voltage back from light to switch with it switched on. sometimes a high resistance connection will show voltage when there's no load, but the voltage disappears when you put a load on.

 

[ruston]

You must have at least dipped headlights on to power the fog light switch up, have you done this. I am sure you have as the tester would have instructed you probably.
Where have you run the new cable from and to?

 

[Specialist]

Hi: Go your local car parts place and buy a 12v test lamp (not led) & use that to test for power at the light, a multimeter (especially digital) can be way too sensitive & show a voltage that isn't really there. I.e a Ghost voltage, a test lamp will only light if there is useable voltage at the fitting.
I keep a test lamp in my car toolbox for exactly your sort of problem.