Ghosts in my wiring

Hi All,

In trying to identify an electrical issue with all the lights not working, working when they shouldnt be and other weird goings on with the lights I decided to take out the instrument binnacle and look for past bodge jobs behind there - and there where many!

One of the things that stumped me was a small circuit board wrapped in sponge and insulation taped to the loom. I have no idea what this is as it goes into the instrument lighting for the dials. The bulbs are standard 12v 5W glass bulbs so its not for colour changing and I cant find any wheel type switch to lower the intensity down so I am stuck.

Anybody come across this before?

Many thanks

What car is it?

Sorry yes, its a 200tdi 1993.

Judged off the pic of the cluster, I'm guessing the vehicle a 90 or 110..

The PCB is likely to be a voltage stabiliser of some sort - which is another guess.. have you looked in the WSM for further info ?

OP:- which lights ? just the instrument lights ? or ?? ..

Hi DiscoBFG, my bad it is a 110 - I thought my avatar would be enough...
I have looked at many sources online and in my manuals and also the LRWorkshop site. Nothing mentions this PCB at all. The lights going mental are all of the external lights - front and rear, fog and reverse included. I originally tried reworking the originals but the indicators, side lights, brake lights, head lights all had really corroded holders and the wiring going to them was hard and brittle. I since replaced most of it properly - opposite twist, soldered and heat shrink wrap.

They all did and still do their own thing for example, indicate left or right and nothing - relay works but lights do not, side lights glowed 10% with each relay cycle. Fog light sometimes lit but at 10%. Headlights worked once for a split second then never again. I have since measured a voltage of 5.49V going to earth on all these lights so I am guessing its a short somewhere.

I took the binnacle out since its getting worse in my opinion and cannot for the life of me get any further forward in sorting it and want to MOT it in next few weeks but thats not going to happen anytime soon now. Since taking the binnacle out I have been able to identify about 6 bodge jobs which are now sorted after I pulled a good 10 foot of surplus cables (2 core 240v flex cable)/relays out all connected using them shi ite blue fold over connectors. The previous owner must of had spots on bumper and roof but not when he sold it.

Going off many post on here I have read about bad earths causing these type of gremlins and was hoping that behind the dash there would of been an obvious one but nada so far, all looks tight albeit with 30years of crud and oxide but electrically they all check out on the multimeter.

Tomorrow I hope to do more testing on the connections, but there are so many earth wires my head is fried today.

ph1978 said:

electrically they all check out on the multimeter.

Click to expand...

MM's are great, but have a fatal flaw - they do not test things under load - it sounds as though you have found this out the hard way - I.E. the circuit will pass voltage, but NOT current ... Your headlamps mucking about are more confirmation of same IMHO.. it's gonna be an earth fault ... always bl@@dy is

I'd make up a long wander lead out of good quality 8 or 10A cable - long enough to reach everywhere on the vehicle from the battery, with a good croc clip on one end, and a good probe on the other end - this will enable you to take a good earth to any point on the vehicle and thus eliminate earth faults in any given fitting ... you can also do the same with the +ve - but a bit more care is needed

You can buy this as part of a device colloquially known as a "power probe" - there are cheap ones on the zone of AMA - and dear ones too .... IMHO you probably need to spend towards £100 to get a proper one... ( autel ps100 is £85 on the zone - genuine power probe 4 is £200 .. )

Don't expect champagne performance at lemonade prices

Disco1 your a life saver.

I did the long earth lead testing which took a while and managed to trace the issue back to the dim dip relay so after discovering that I came back on here and searched for that and low and behold there are a fair few issues with them, luckily there is a simple fix which entails removing the innards and jumpering the connections internally.

I will do this over the coming days and report back.

A massive thanks for the technique! Brilliant.

ph1978 said:

Disco1 your a life saver.

Click to expand...

Thanks - I'm here all week ... ...

In reality it's probably just lots of experience of LR and the Prince of Darkness

So i pulled the dim dip relay out and opened it up, it was spotless inside so tested it on a 12v supply and it seemed to work so I put it back in and everything sort of worked again, no more weird goings on but still down left front headlight and left hazards not coming on although the left indicators work fine. It looks like its been a combination of bad wiring, old connections and bad earth making for one messed up situation.

I will rewire the left headlight again tomorrow as far as I can without taking the wing off, might have to create a new section bypassing it from the bulkhead and work out whats happening with the hazard wiring. Other than that everything is now within reach again!

Thanks again for the advice which fast forwarded me a couple of weeks I reckon, cheers Disco1!

IMHO, it's worth doubling up on the various earth straps, adding some additional ones at suitable points, and also worth making cleaning them part of the routine maintenance of the vehicle.. it's as boring as hell, but it is what I do, and seems to work .. .

Caig DeOxit is a superb chemical verdigris remover ... it's expensive, but good value

If you have a hand brake cable, check it for integrity, as with other earth returns failing, this can become the main earth, and get hot, losing its temper ( spring temper ) - at which point it isn't a cable any more ...which won't end well

I think I get you - when you say "hand brake cable" are you referring to an earth cable that`s gone really hard and brittle?

ph1978 said:

I think I get you - when you say "hand brake cable" are you referring to an earth cable that`s gone really hard and brittle?

Click to expand...

Nope - as typed - some 110's had a linkage to work the HB, some had a cable - don't know which yours is.. so, literally, the cable which operates the HB ... ..

Ah okay got you, pretty sure mines a cable then but a good point to check as I am not 100% certain. Also now understand what you mean by it not being a cable after becoming the main earth! I was under it today and there is a battery sized cable from chassis to transfer box which i took off, cleaned and put back on - might of helped in the gremlin issue come to think of it! I defo agree on adding extra earths around the body and chassis as there are some bare earth braids that are just dangling in the wind once connected to something in the engine bay so its certainly lacking what it had from factory. My spreadsheet list of jobs grew by 3 just now! Add verdigris chem, suss out HB method, audit earthing.