Tail Lights / Parking Lights / Dash Lights all blown at same time (2009 GU ZD30 DI)

So I've been trying to resolve this for far too long now. All the lights on the tail light circuit (Tail Lights / Parking Lights / Dash Lights) have all blown at the same time. I have replaced all the bulbs as well as the fuse (not blown?) and still can't get the lights back on.



It's possible the wrong fuse was in when they blew (15A instead of 10A) as while initially troubleshooting for the dash lights out I remember discovering an incorrect fuse. This was however before I realised all those lights were on the same circuit so I'm not sure if it was the tail light fuse or not.



All the threads I have found suggest the combination switch is the issue however, as far as I can tell, I don't believe it is. I have removed it and checked the circuit for continuity. Checking the circuit from before the switch component to the output shows the switch registers open and closed.



I have traced as much of the wiring as I can and cannot find any rubbing or loose connections.



All other lights (headlights, indicators, brake lights) work however it should be noted both my headlights blew around a similar time.



I'm out of ideas and am restricted to day driving so any help is greatly appreciated.

Having a larger fuse won't be the cause. Firstly, try another fuse. It might not look blown but very well could be.

Next, check your trailer plug for a fault as that is the only place you have really cut into the loom. These are the most common cause of that circuit.

It's the biggest circuit in the car so chasing the fault can be daunting. I would 100% be thinking of anything you have done to the car, anything you have added, any bolt or screw you added or changed recently and work back from there.

Check and try a new fuse 1st. Does it blow? If you reckon your fuse is OK but the circuit is not live then I'd put money on thr fuse not being ok.

Do you know how to use a multimeter? Ohms? 12v DC. ?

1. Check fuse by using a new fuse.
2. Check you have 12v on the hot side of the fuse.
3. Check Ohms across fuse and across the globe v earth anywhere on the car.

Thanks for the prompt response. My knowledge of electronics is okay (I can work through ohms law etc.) but my application is poor as I have little real world use.

I have tried multiple fuses so I am reasonably confident it is not that but I will run a multimeter across it to confirm.

There is a trailer plug which is pretty old (I've never personally used it - I bought the car used) which I had a play with but short of removing it I wasn't sure what to do. Is there a way I ca test this?

I'll also go have a go at checking ohms across the globe/earth and see what it registers.

The only incident I can think of close to when it occurred is I ran the battery flat (left lights on over night - rookie move :1056:) and had to jump the car. The only other thing would be I installed a new stereo about 6 months prior but I can't really see how that would suddenly become a factor.

Again, thanks for the help.

To update the thread with the resolution:

I discovered a pinch in the cable at the trailer plug which must have led to a short. Tracing all the wiring back, I found an inline fuse under the bonnet. This had completely burnt through - half of the fuse had melted and even melted the case it was in.

After replacing this we were back in action.

Thanks for the update. It might just save someone else with the same fault. I have encountered a few inline fuses with melted cases ,so I usually replace them with better units.

To update the thread with the resolution:

I discovered a pinch in the cable at the trailer plug which must have led to a short. Tracing all the wiring back, I found an inline fuse under the bonnet. This had completely burnt through - half of the fuse had melted and even melted the case it was in.

After replacing this we were back in action.