Technical Reverse light keeps blowing it's fuse!

[Mark075]

This is a head scratcher. I noticed my reverse light wasn't working (when I was reversing suprisingly) so I checked the bulb. It looked fine so I put in place of the fog light to check it. It worked fine in there. I then put the bulbs back in their rightful places.

I then checked the fusebox and found that it was 5a fuse and was blown. Looking at the manual it should be 7.5a so thought that was probably the problem. I didn't have a spare 7.5a so I stuck another 5a fuse in its place. This blew as soon as I put the car in reverse.

The next best fuse I had was 25a. Perhaps misguidedly, I placed this in the fusebox and then put the car in reverse. This blew the 20a fuse in the engine bay which prevented all functions on the car from working (quite worrying at first until i found the fuse!!)

There is clearly an issue with the wiring causing the fuse to blow everytime. Has anyone experienced anything similar or have any ideas? It's not a massive issue now but may be when MOT time comes round.

Cheers

 

[Matthewr1990]

How about just try the fuse that it requires as you haven't seemed to do that yet. If It blows again I wouldn't know hat to do other than tearing cables using a multimeter to check what power is getting to and from places.

 

[Mark075]

If it blew a 25a fuse, surely it will blow a 7.5a fuse won't it?

I'll give it a go though.

 

[neilshep]

If it blew a 25a fuse, surely it will blow a 7.5a fuse won't it?

I'll give it a go though.

It is pointless trying different fuses. The is clearly a faulyt in the wiring, live shorted to ground. Check the wiring in the most vulnerable place, where it is exposed from the reverse light to as far back as you can trace it.

 

[carlorff]

It is pointless trying different fuses. The is clearly a faulyt in the wiring, live shorted to ground. Check the wiring in the most vulnerable place, where it is exposed from the reverse light to as far back as you can trace it.

He wrote what I wanted to write myself.

 

[Marcos999]

Ideally you need a multimeter and you're probably going to find the bulb side of the fuse holder is shorted to earth (the car body). You've then got to find the short. Have you had a good look behind the rear light cluster to see if the loom has caught the body?

 

[Mark075]

Thanks for the advice. I hadn't thought to look behind the light cluster as the reverse light is in the bumper. I shall have a good look around.
Strangely my cruise control has also stopped working entirely. The light on the dash will ocassionally flicker on if I switch it on but then it immediately dies (and advises cruise control off). Could there be a connection?

 

[neilshep]

Thanks for the advice. I hadn't thought to look behind the light cluster as the reverse light is in the bumper. I shall have a good look around.
Strangely my cruise control has also stopped working entirely. The light on the dash will ocassionally flicker on if I switch it on but then it immediately dies (and advises cruise control off). Could there be a connection?

Most unlikely. The cruise control connects into the engine computer. The reverse light will be controlled by the reverse switch on the gearbox, via the body computer, and relay.

See the fault finding guide!

 

[Mark075]

Thanks for that - very useful. Plenty of points to check. Cheers.