Reverse light problem
 

Hello

The reverse lights have not worked for some time on my rover CDt. I investigated today and found with the rear lamp leads disconnected, I get 12v. Connect them and it goes to 0v.
Tested the switch and it works perfectly.
I found a junction box behind the glovebox with green and brown wires, approximately 7 wires. With the rear lamps disconnected it reaches 12v, but then drops to 0v with reconnected. Tested continuity of the rear lamp wires and all good.

After a bit more digging its header k109, connector C0286

Anybody have a clue as to what might be wrong?

regards

James

Year ?
Automatic or manual ?
:wantpics:

Ignition on, short the terminal on the switch to ground, do the reverse lights come on?

The switch in the manual car is a common problem - it works fine if you remove it and test it, but putting the car in reverse, the switch is often not pushed hard/ far enough to put the lights on.

The 'nose' of the switch needs to protrude further into the gearbox, to work properly. There are three possible fixes...

1. Try a new switch
2. Add a blob of solder to the 'nose' of the switch.
3. If you have access to a lathe, turn down the flat face hex, so it can be screwed further into the gearbox. It needs to go around 2 or 3mm further in.

Its 2002 Manual bog standard club with no bells or whistles. Not sure what photos would achieve to make this post more worthy.

I shorted the switch connector and nothing. K109 behind the glovebox is the feed to all things connected with the reverse switch. Pin 19 is the one fed from reverse switch, and when its in reverse gear, ignition on I get 12V. Move it out of gear and it returns to 0V. This rules the switch out.

Testing continuity again shows pin 15 LH reverse light circuit is open but RH see's 12V. But I did get 12V on LH when first checking. It appears that the problem lies between glovebox K109 and rear connections. Is there another connector buried in the car under seats?

On the RH rear connection, there's 12V but as soon as the bulb is fitted it goes to 0V. Can't be an earth issue as the rear lamp bulb holder is common earth and the other lamps all function.

Sorry cannot find my circuit diagrams, so I'm guessing...

That reads as if it is not a genuine 12v, rather it is fed by an high resistance or a bit of stray voltage - guess you are using an high resistance digital test meter?

The proper way to be sure you have a genuine 12v is with a 12v lamp.

The front to rear loom runs along the right hand side of the car, just under the carpet, in the corner by the door. The cable for the reversing light, might call into the right hand rear wing, where the reversing sensor module normally goes (when fitted).

Have you found/checked the reversing light fuse?

Found my MII diagram, it will not be the same as your MKI, but might give some clues...

The gearbox switch operates a relay, the relay then powers the reversing lights. You need to track down that relay, probably behind your glovebox and see if it clicks, when reverse is selected, with ignition on. The wire from the relay running to the reversing light, on the MKII is a black cable.

I checked fuse 41 10Amp and its OK

If its not raining tomorrow might have a go at finding the circuit under the carpets

According to the RAVE wiring diagram, there are two Green/Brown cables from the joint behind the glove box to the reversing lights (no other joints on the way), one from pin 17 to the left light, one from pin 15 to the right.
As above, if fitting a bulb changes the status from 12v to 0v, it usually indicates a 'stray' voltage rather than the full 12v on that cable, possibly caused by damage to it, or 'feedback' via a bad Earth connection.

Hi James,

Just to clarify, the relay mentioned earlier is for automatic transmission only so you won't have one.

When you shorted the reversing lamps switch to earth earlier the fuse should have blown. As it didn't, you must have high resistance upstream of the switch. I'd suggest checking the fuse box wiring physically. The diesel is known to have problems in that area.

Simon

As I read post 4, the switch contacts were 'bridged', rather than connected to Earth.

I would check with a testlamp rather than a meter the 12v at the connector behind the glove box, if that works OK, it indicates a problem between the connector and the light, rather than between the fuse panel and the connector..