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Reverse light not working


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Got the MOT on Saturday so thought I'd test out the lights which always seem to fail at this time of year. Fixed most but I can't figure out the reverse light. The bulb is fine as is the fuse and I seem to be getting 11.7v at the fusebox but only 0.2v at the wire in the rear tub. Where might the volts be disappearing to? I've followed the green/brown wire back to the chassis and it all looks fine. I don't really want to cut it to test what the voltage is there as it's likely to become a weak spot in future. Any suggestions for an electrical numpty?

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I had the same problem with my Disco. On the R380 gearbox the reverse light switch is activated by a steel block - this hasn't been case hardened sufficiently and a groove wears in it, caused by the reverse light switch plunger and consequently the plunger isn't depressed far enough for the switch to close the internal contacts. The only solution I could come up with was to remove the gear selectors and the block and run a weld where the worn groove was and then file it back. The weld is harder than the block and if you do this you wont have any more problems, the other solution I'd guess is to replace the block.

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You might just need to wind the switch in a bit assuming you have an LT77 gearbox. If it's an R380 a new switch would be it required as these arnt adjustable.

Failing that.... Select reverse and with a test light or multimeter check you get battery voltage at both sides of the switch when reverse is selected and the ignition on. If not the fault is between fusebox and switch, if it is then the fault is between the light unit and the switch. If there is no fault there then the fault is between the bulb and the route to earth.

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All that Vulcan said, I was assuming (which makes an ass out of you and me) that you had tried all the electrical tests. I replaced the switch on my R380, believing that the probe was worn and still had no joy as the groove worn on the reverse actuation block - for want of a better description - was worn too deep to depress the plunger into the switch. Replacing the switch on a Disco is an absolute bitch of a job as you need to drop the gearbox crossmember to gain access to it - either that or remove the front passenger seat, pull back the carpet and drill a 2" hole and plate it over afterwards.

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Thanks guys, never assume anything when it comes to me and electrics! I hadn't considered the switch so took that off, cleaned up the connections and tightened it up again and it's all working again.

Also useful to know it's not part of the MOT test if I can't get it working next year!

Richard

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  • 2 years later...

Reversing light stopped working (2008 Defender Puma 110).  After reading forum threads I checked fuse and replaced reversing light switch. Frustratingly, this did nothing. I swapped the fog light with the reversing light so I could manually have illumination. Weeks later I noticed both rear number plate bulbs had blown and replaced them.  As if by magic and perhaps by complete coincidence (as I can see no logical explanation), the reversing light (swapped back) is now working again and has continued to work since.    

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  • 4 years later...
On 9/23/2015 at 10:46 PM, Boydie said:

I had the same problem with my Disco. On the R380 gearbox the reverse light switch is activated by a steel block - this hasn't been case hardened sufficiently and a groove wears in it, caused by the reverse light switch plunger and consequently the plunger isn't depressed far enough for the switch to close the internal contacts. The only solution I could come up with was to remove the gear selectors and the block and run a weld where the worn groove was and then file it back. The weld is harder than the block and if you do this you wont have any more problems, the other solution I'd guess is to replace the block.

Hi, I'm an electrician not a mechanic of any sort. I have tried everything now (even took a mm of the inside face of the switch to see if it would with the contact ball going in further, but still no luck)

has the gear box got to come out to access the gear selectors to do this modification?

Cheer

Paul

South Wales 

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Hi Mo

Many thanks for your prompt reply. 

The original switch has a ball bearing, so obviously what ever actuates it slides past to depress the switch. 

What I did was pop the switch to a mate who has a lathe and we turned 1mm of the inside face of the fixing nut so the switch could go in further but this didn't work. ( I read a post where someone had done this and it had worked for them)

I'm reluctant to take any more of the nut as there is very little movement on the ball bearing, the part number is LR005160 if you look at a picture of it you will see what I mean.

So it looks like my only option is to sort out whatever it is that depresses the ball. (depressing me at the moment 🙂)

The problem is that you can't see up inside the hole where the switch is to see what is going on, even tried taking a photo without any luck.

So I don't know to go from here

Cheers

Paul

 

 

 

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If this is a silly question I apologise, but are you 100% certain that if you work the switch outside the gearbox (you may need to earth the body) that the reverse light works? In other words you may have 2 problems, one mechanical, one electrical (it's a Defender)

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Hi

Many thanks for your reply

Yes the light works fine if I depress the switch when it is removed (or short it out).

I did notice one thing though, that the switch make then breaks on the ball over travel. I don't live far from Bearmach, I'm going to pop there tomorrow and see if i can get an OEM switch and test that. The new one I bought looked fine but its an aftermarket one and I don't like the sound of the click inside it.

If all else fails I'll change it to a proximity sensor, I'll just need to do a little research to find a suitable one. I used an endoscope camera earlier and I can see the actuator and think a decent proximity switch would work.

cheers

Paul

 

 

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  • 1 year later...

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