Location Of...?

Hi Bob

Sounds a typical poor earth problem. It's a while now since I had a Mk1 but I seem to remember that earthing problems can be caused by the multiple earth connections on the o/s inner wing. Check any you see, disconnect the leads, clean all the connections and then reassemble with with the application of a little grease.

Peter.N.

Hi Peter

I've cleaned the earth connections on the inner wings, thought I'd check any others I could find but can't seem to detect any more. Looked behind the rear light clusters but the only earth I can see is a small self tapper that has been put there to earth something on the towing bracket (I think) Would there be any earthing points behind the dashboard area or on the scuttle? I've got half the dash off at the moment anyway so dismantling some more won't be too much trouble.

Bob

Hi Bob

I am not aware of any others but that doesn't of course mean that there are none. It does seem strange that the earthing for the rear is done at the front, but I think that is how it works, probably something to do with cheapness of manufacture!

Peter.N.

If in doubt just wire in a new earth to something solid in the boot.

Ciarán

Excellent idea!

Bob

Hi Bob

The earths in the side wings at the tailgate are one each side from the tail lights. Single core yellow wires running from one of the two blue 4 pin connector plugs that supply and fit into the back of the white bulb panel. They go to eyelets bolted to the chassis but it is usually at the bulb panel end that has verdigris on the contacts. If anyone has added a tow bar (includuing Cit dealers, no tow bars were factory fitted to XM's) then extra wires may well be added to these plugs. I have found cases when an extra wire or two has been pushed into the earth contact of the plug relying for onwards earthing on the single original earth wire that is now loosened in the plug. Take any of these extra earths back to an eyelet on the chassis earth bolt. For the tailgate the earth comes out near the hinges in the main bunch of cables (one each side). There are eyelets and earth bolt on the chassis roof cross member under the rear cross trim. These earthing wires are very important on estate tailgates which are of fibreglass and not metal construction.

Regards

XMexc

Hi Xmex
Thanks for the info, I've rechecked the connections on the front inner wings and remade the 2 cables that run from the wing to the negative terminal on the battery as they seemed a bit loose where they were crimped into the clamp. None of this has made the slightest difference to the reverse light problem but at least now I feel fairly confident that I can discount any of the earths at the front of the car having anything to do with it. Next stop will be checking the rear end cabling including some decent connectors for the tow bracket wiring instead of the nasty looking bunch of snaplocs that are there at present and some additional earth points. Didn't realise the tailgate was fibreglass, as a Lotus owner I'm used to adding extra earth bolts.

Bob

Hi Guys
Just an update on my reverse light problems and proof if it were needed that electrical gremlins stand more chance of being solved if there's a decent wiring diagram to hand. Having sorted the broken tailgate cables to no avail and armed with Noz's excellent cd manual the fault was finally found, basically at some time in the past there's been a Muppet under the bonnet who managed to connect the rev counter feed to the reversing light switch and the reverse light cables to the rev counter speed sensor!. I discovered this after cleaning all the grime off the loom and connectors, revealing a brown plug pushed into a black socket, that's where the diagrams came into their own having not only the cable colours but also the connector colours as well. Now the left hand dot matrix display has started sending more messages as well, which haven't appeared since I've had the car. Someone had also bodged a feed cable from the speed sensor to the rev counter to make it work which has now been ripped out, I imagine that was done after they'ed managed to bugger up the other connectors and wondered why the rev counter had packed up!

Bob