Disco 1 lights and dash lights dim when indicators are on.

Georgeblade · Sep 8, 2022

Hello,
I am in need of help please.
My 200tdi pre facelift has developed an earth fault (I think).
When I put an indicator on the dash warning lights start to dim in time with the indicators.

If the lights are on then all of them start to dim with the timing of the indicators.

So, removed and cleaned all the earthing points I could find - the ones on the front inner wings, the fuel tank fuel sender, checked and tested the main battery earth lead and the engine to chassis earth.

All to no avail.

I've also pulled every tail light and indicator light bulb and cleaned them. Also removed and cleaned the flasher unit contacts.

I can't find where the tail light clusters earth onto the body and I cant find where the instrument panel earth is.

Can you help please.

Colthebrummie · Sep 8, 2022

I dont know the disco wiring but if I have earth problems, rather than chasing them down, I just put new earths in. Much quicker than fannying about but you do end up with more wires so keep the new earths to the original earth wire colours.

Col

Disco1BFG · Sep 8, 2022

Colthebrummie said:
I dont know the disco wiring but if I have earth problems, rather than chasing them down, I just put new earths in. Much quicker than fannying about but you do end up with more wires so keep the new earths to the original earth wire colours.

Col

+1 - provided you keep to the OEM colours, this will work and not be too confusing.. = works for me

Pretty sure the earths for the IC are in the footwell.. worth a nosy, but be prepared to find some corrosion

Georgeblade · Sep 8, 2022

Colthebrummie said:
I dont know the disco wiring but if I have earth problems, rather than chasing them down, I just put new earths in. Much quicker than fannying about but you do end up with more wires so keep the new earths to the original earth wire colours.

Col

Worth a go. Although I have used a long wire clipped to the rear light cluster(s) earth wire and run direct to the battery -ve with no effect.

Georgeblade · Sep 8, 2022

Disco1BFG said:
+1 - provided you keep to the OEM colours, this will work and not be too confusing.. = works for me

Pretty sure the earths for the IC are in the footwell.. worth a nosy, but be prepared to find some corrosion

Sounds like I'll be digging the dash out (again).

discool · Sep 8, 2022

Georgeblade said:
Sounds like I'll be digging the dash out (again).

I take it this issue is with the engine is running and the alternator is spinning, and therefore not low battery power.

sierrafery · Sep 8, 2022

discool said:
I take it this issue is with the engine is running and the alternator is spinning, and therefore not low battery power.

+1^^^

... though worth a voltage check on the battery too while the symptom occurs to not be a voltage drop due to alternator misbehaviour, also there is some common weak contact issue on early 200tdis which have some fusible links wrapped in the main power harness after the battery somewhere and voltage is lost between the battery and some circuits

Georgeblade · Sep 8, 2022

discool said:
I take it this issue is with the engine is running and the alternator is spinning, and therefore not low battery power.

Yep, battery reads 13.7v when running.

Georgeblade · Sep 8, 2022

sierrafery said:
+1^^^

... though worth a voltage check on the battery too while the symptom occurs to not be a voltage drop due to alternator misbehaviour, also there is some common weak contact issue on early 200tdis which have some fusible links wrapped in the main power harness after the battery somewhere and voltage is lost between the battery and some circuits

I'll take a close look st these links. It does seem to me the prefacelift D1 has quite fragile electrics.

sierrafery · Sep 8, 2022

Georgeblade said:
Yep, battery reads 13.7v when running.

You have to check voltage on the fusebox after those fusible links if your's is so early modell to be within the VIN range described in the attached bulletin cos if it's a bad contact in that part of the loom the voltage is good on the battery but drops after the FLs under load if tha's the case even though it looks more like an earth issue

Georgeblade · Sep 9, 2022

sierrafery said:
You have to check voltage on the fusebox after those fusible links if your's is so early modell to be within the VIN range described in the attached bulletin cos if it's a bad contact in that part of the loom the voltage is good on the battery but drops after the FLs under load if tha's the case even though it looks more like an earth issue

Thank you for this, my chassis number begins KA and has these dodgy fusible links.
After 29 yrs they could well be the problem.
seems to me a small fusebox in the engine bay on the inner wing would be a good replacement.
Unlikely to be able to get the original LR kit.

Georgeblade · Sep 9, 2022

sierrafery said:
You have to check voltage on the fusebox after those fusible links if your's is so early modell to be within the VIN range described in the attached bulletin cos if it's a bad contact in that part of the loom the voltage is good on the battery but drops after the FLs under load if tha's the case even though it looks more like an earth issue

..... there are recent new issues - the temp gauge only shows the temp. on the first white marker but goes up when the headlights are on, and the rev counter sits on zero after start up until the engine is revved quite hard.

Georgeblade · Sep 11, 2022

sierrafery said:
You have to check voltage on the fusebox after those fusible links if your's is so early modell to be within the VIN range described in the attached bulletin cos if it's a bad contact in that part of the loom the voltage is good on the battery but drops after the FLs under load if tha's the case even though it looks more like an earth issue

Hi, sorry to be a pest, just tested the feed voltage drop with sidelights on.
Across the battery terminals its 12.57v.
Across the battery positive and one rear tail light +ve terminal its 11.52v.
The drop is 1.05v. It seems excessive to me, but is it? I have no idea what the normal v drop should be.
Any help always appreciated.

sierrafery · Sep 11, 2022

Now measure with indicators on too

Georgeblade · Sep 11, 2022

sierrafery said:
Now measure with indicators on too

I did, the drop us even bigger, more like 2.5v.
Could it be those fusible links wrapped in gauze?

sierrafery · Sep 11, 2022

So seems that the lights are fading due to the voltage drop, i dont know how can you fix that other way than in that bulletin or rewiring and fitting a 300tdi fusebox

Georgeblade · Sep 11, 2022

sierrafery said:
So seems that the lights are fading due to the voltage drop, i dont know how can you fix that other way than in that bulletin or rewiring and fitting a 300tdi fusebox

Looks like a 300tdi fuse box is needed.
Many thanks for your help.

Georgeblade · Oct 9, 2022

Well,
I am stumped.
Still got the faults after:
Cleaning all earth points I can find;
Replacing the in wire fusable links with midi fuses on the +ve supply;
Taking every bulb out and cleaning/replacing;
Replaced the alternator.

So, could it be a faulty indicator unit? Just had some welding done and I know they aint great at disconnecting the battery.

Any thoughts or ideas?

discool · Oct 9, 2022

You have two fusible links associated with indicators to test, so there two places to check that battery voltage is present, first at the hazard flasher switch the other is at the ignition switch, both have separate feed, therefore find the brown feed wire and check the voltage any less will indicate an issue with a fusible link, if so install a temporary feed, bat + to the ignition switch or hazard switch to see if theres any improvement.

There was a kit available for the early RR and maybe still is to replace the fuses and was supplied to replace them, basically from a picture I’ve seen in one of my manuals its bunch fuses with a tail solder on each end plus a couple of gel filled crimp for each fuse … simples.
A lot easer then finding a location for an engine bay fusebox and making up a loom for wiring to run to and from the fusebox to the vacant position where the fabric covering and the fuses use to be..

Georgeblade · Oct 10, 2022

discool said:
You have two fusible links associated with indicators to test, so there two places to check that battery voltage is present, first at the hazard flasher switch the other is at the ignition switch, both have separate feed, therefore find the brown feed wire and check the voltage any less will indicate an issue with a fusible link, if so install a temporary feed, bat + to the ignition switch or hazard switch to see if theres any improvement.

There was a kit available for the early RR and maybe still is to replace the fuses and was supplied to replace them, basically from a picture I’ve seen in one of my manuals its bunch fuses with a tail solder on each end plus a couple of gel filled crimp for each fuse … simples.
A lot easer then finding a location for an engine bay fusebox and making up a loom for wiring to run to and from the fusebox to the vacant position where the fabric covering and the fuses use to be..

Many thanks.
I'll try the temp +ve feed as you suggest.
I have dumped the fusible links in favour of a set of fuses (photo attached).
This fault is a real head scratcher.

Disco 1 lights and dash lights dim when indicators are on.

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