No rear number plate lights

[andysheep]

Well one of my mot fails is the rear number plate lights,i thought removing all the crapy hacking of the rear part of the loom to put in tow bar electrics,but after tidying it up no joy and testing with volt meter thingy,on the continewty setting the bulb has good contact,but removing the bulb i still had continewty,so i guess this why i dont have power to the plate lights,is it a short or is it linked to the lack of the gauge lights in the binnacle too,i think maybe the head light switch is bad,any ideas,anyone?

[Brianmoooore]

Dash lights and number plate lights are the same circuit - all lights that aren't required when parked.
They share a fuse with one of the tail and side lights, so it's not a fuse that's blown. They do use a separate section of the lighting switch, so that's a strong possibility.

[andysheep]

Thank yet again brian,so im hoping a new head light switch sorts this,and i tried changing the binacle bulbs and nothing,and the fog light switch didnt work either but i tested the switch and it seemed buggered because when i jumped the fogs came on,so bad switch,should i be worried both are faulty?this was a cheap car,and i checked old mots on line and its noted non working rear number platelights,its a shame cos i fixed most other problems thamks to you,and im very grateful.
Andy

[paultv]

It's more likely to be the Rear Light Check Relay. The feeds for all rears including the number plate lights go through this unit. Basically it has small reed switches for each lamp circuit, which close when current passes through a coil wrapped around the switch, on its way to each bulb. This then indicates on the Active Check Control whether or not a bulb has blown, so there is one reed with its associated coil for each bulb.

The circuit board on which this passive bit of electronics sits cannot handle excessive current, the tracks often burn out, or less often, the reed switches fail giving a false indication of bulb failure when your lights are still good.

In your case, it sounds like burn out as you say the wiring has been messed with.

On my Cabby, this relay unit is hidden below the nearside rear window, accessed by removing the rear seat, and rear "door" inner panel trim, two cross head screws release it, just loosen them and the unit slips out.

It's easy to open the relay, after removing the connector, and easy to do a visual check for failure points on the board or burnt out coils, a test meter is handy here, also soldering a heavy gauge wire across burnt out tracks produces a perfect repair.

IIRC the relay lives in the boot behind the nearside hinge, aerial area, on non cabby cars, but not too sure.

Hope this helps.

Paul

[Brianmoooore]

Lamp check module (assuming this car has one - 6 cylinder cars only) can occasionally fail, but it would be a remarkable coincidence if this was found to have failed at the same time as the circuitry that precedes it (dash lights) was also out of action.