LONG POST 300tdi 90 electrical fault driving me nuts!!

Hi,
Following on from the thread about the heated rear windscreen fault some time ago, my 90 has developed an intermitent fault with the
indicators. Here's the symptoms and what I've done so far:-
Sometimes; operation of the left indicator causes the 10A fuse for that circuit to blow instantly. Replace fuse blows again instantly. Operation of the Hazard warning flasher(different fuse) is unaffected. Remove steering wheel and steering column cowl, disconnect combined indicator switch/headlight dip-main-flash/horn push at multiway connector. Using an old fuse in the relevant position, as a test lead connected to a multimeter on 10A scale proves that the fault is still present when using a jump wire between the relevant pins in the multiway connector - OK so it's not the switch. BUT the HRW is now working prefectly!!
Give up for the evening. Next morning the fault has gone and the HRW still works! Remove the small panel housing the Hazard warning switch, the Rear fog lamp switch, and the HRW switch. Inspection of wiring behind here looks undamaged. Removal of Hazard switch renders indicators inoperable(as it should), and check this switch for short circuiting - nothing wrong here.
Remove instrument panel, and check wiring behind here for anything appearing likely to cause an intermittent short circuit. Locate several connectors showing bare conductors and separate and insulate ALL thoroughly. Fault still not present, poke and probe all the accessible wiring harness to see if the fault will reappear - it doesn't!
Replace everything so far removed with the exception of the fuse(leaving the multimeter and test lead in it's place). Next day check to see if faut has reappeared before starting engine - it hasn't - BUT the HRW isn't working again(which by the way, will work with just the ignition ON and no engine running). Start the engine and check the indicator again - the fault is back!!
Other things checked so far include the indicator relay, it's socket, and the indicator lamps themselves, which work without fail on Hazard warning when the indicator fault is present. Fuse box mounting removed from bulkhead to check wiring behind - nothing here!
OK this is giving me a headache! I wonder if any of the more experienced engineers here have had anything like this before and has a "check this first" tip. One of which I have already heard which is that a fault with the indicators, is often due to a fault inside the Hazard warning switch. However, seeing as how this switch costs GBP53 + VAT, I'm reluctant to replace this without maybe borrowing one first
Any helpful suggestions most gratefully received.
TIA
Neil
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On 14/03/2010 20:06, Neil wrote:

Fuse panel.
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Nige wrote:

On our 90 the indicumator relay is mounted behing the panel! Lucas Prince of Darkness and the keeper of lectrik smoke.
--
GbH

Wisdom and experience come with age, they say, but I do wish I could
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You've got my sympathies. I'm currently chasing an almost identical problem (without the hrw issue).
The hazard switch and wiring are pretty easy to check before spending money on a new switch. This is useful
http://forums.lr4x4.com/index.php?showtopic=25376
If needed you can get a new hazard switch (Lucas) much cheaper than LR dealer prices. Have a look at Island4x4 on ebay - paid about 15 for mine.
Do you have a copy of the 300Tdi wiring diagram book?
Colin
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On Mon, 15 Mar 2010 09:53:47 -0700 (PDT), Colin Reed

Thanks for the replies so far guys.
Just to update:
I can find no fault at the fuse box - removed it and carefully checked every wire on the back for stray conductor strands, contamination, loose or corroded fuse sockets.
The flasher relay in my 90 is mounted next to the wiper delay relay on the same bracket as the fuse box, and works perfectly when indicating Right and when using the Hazards.
I've removed the Hazard switch and tested it according to the method in the Colin's link and it switches internally just as it is supposed to. While the switch remains out, I have linked the multiway connector as will allow operation of the indicators - just as in the write-up. And for the last day and a half, the fault has not re-appeared. But when I came to start up this evening, the fault was back again as soon as the engine was running. Just to confound me further, 5 minutes later the fault has gone again. So I think I can rule out the switch as the cause! I'm coming to the unwelcome conclusion that there is an intermittent short circuit somewhere in the loom, and possibly somewhere where this circuit and the HRW circuit run close together. This where a wiring diagram of the loom/harness would be much more useful than the only diagram I have which is not unlike a Haynes wiring diagram, which bears no resemblance to the layout of the wiring. Is the 300Tdi wiring diagram book any different Colin?
Next test is to measure the current flowing without the flasher operating, to the indicators, each side in turn and compare. Ho Hum!
Neil
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Neil wrote:

Have you checked the relay? They get wet easy due to leaking screens, also check the wires behind the dash?
--


Nige,

Land Rover 90
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Sorry for the delay in getting back to you on this one Neil. The wiring diagram book is very useful and much different to the Haynes variety. 32 pages in total. Email me colin (guess this character) reedx.net
Colin
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On Tue, 23 Mar 2010 10:11:56 -0700 (PDT), Colin Reed

You got mail - hopefully!
Neil
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No nothing. Try reedxuk [ a t ] gmail.com
Colin
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On Tue, 23 Mar 2010 10:11:56 -0700 (PDT), Colin Reed

Many thanks Colin, that is THE best vehicle electrical documentation I've ever seen - incredible!
Neil
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snipped-for-privacy@thisaddy.com says...

Hi.
As it's only the left side that's giving the problem, that should be a BIG clue. There is an intermittent short to ground on the left circuit somwhere... To "blow instantly" a 10A fuse, needs well over twice that current, so it will be a good one! (Short circuit that is.)
Any of the lamp fittings (including the tel-tele lights in the dash) or the trailer/towing socket and associated electrics, if fitted, maybe the column stalk switch too, and of course any chafed/frayed/cooked wires.
The Hazard switch though relatively complicated, is still a simple thing, and as it is rarely used, is therefore less likely to give problems than even the column stalk switch. That's not to say the never give problems, more like the indicators misbehave after you've "Had" to use the hazards in anger (or during an MOT!) is more usual than blowing fuses...
The "Indicators" are powered by the engine on feed. The "Hazard" supply uses a seperate "always on" feed (with it's own fuse) direct to the Hazard switch, that in turn feeds the flasher relay when enabled and so on.
If no fuses blow when the Hazards are used, the only thing "bypased" is the main stalk switch, so that should be looked at closely (not easy.)
Get a book with the relevant correct (for your vehicle and year) diagram in, and use that for propper methodical diagnosis, rather than poke and hope. There is a French website somewhere with a load of LR wiring diagrams on, in downloadable format. But you'd need a very good printer (A3 preferably) and I can't find the site right now.
Defender electrics are not that complicated. But following the physical wiring can be a headache to say the least. If it's not be "altered" by you or past owners, work by following wires with the same colour code as appears at an external lamp fitting.
Fit an old style (non halogen) headlight bulb in place of the fuse that blows (both filaments in parallel) That should allow the indicators to work relatively normaly (at a different flash rate perhaps) but if a short appears, it will suddenly "light up" bright, so you can go fiddling to find the problem without eating fuses, or starting fires.
Lastly, take care. Low voltage but High current faults, can still hurt (very nasty burns, so take off any rings etc when working on electrics) and of course start fires. I've had one in a Series III when driving, not nice. The whole loom and dash went up, when I turned on the lights one evening, as a wire at the back had chafed. I couldnt turn it off as the switch welded "On", and Solihull in their infinate wisdom did not fuse the obligatory lights feed (Dispite there being a "spare" fuse!)
Do not "bodge" electrical repairs, I was lucky I was on a straight road I know well, with nothing to hit.
DJB. Going outside to see about re-flaring a clutch pipe, to stop a small but messy fluid leak, after changing both cylinders the other day.
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Dave Baxter wrote:

Could try the old slo-blo fuse, 6"nail! Look for where the Lectric smoke is escaping!
--
GbH

Wisdom and experience come with age, they say, but I do wish I could
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On Thu, 18 Mar 2010 10:43:46 -0000, "GbH"

Mucho continuing thanks for the on-going help. All suggestions are being, will be, or have been followed.
Good suggestions Dave, I have eliminated the stalk switch by disconnecting it and using a metallic link across the multiway connector - fault still there. It is entirely possible that the HRW issue is totally un-connected(pun intended).
I have not yet removed all of the dash in order to inspect the wiring between the rear of the instrument panel and the fuse box, as I'm having to continue to use the vehicle in between faulting sessions. When I've got a few days of lay up time I'll get it off and have a look-see.
New to the equation is the failure tonight of the brake lights and the reversing light.
I'll be having another bash tomorrow.
Most grateful guys.
Neil
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Neil wrote:

Have you checked the ignition switch?
--


Nige,

Land Rover 90
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wrote:

No, not yet, but I have found a bad connection in another multiway connector in the engine bay, the cleaning of which has restored the reversing light and the brake lights.
I'm beginning to think I may be chasing multiple faults here with a cumulative effect. I had the vehicle up on ramps yesterday to inspect the harness from the rear cross member all the way along the chassis to the engine bay - no damage apparent there. There is still a mess of wires behind the off side rear tail lamp that needs a lot of re-terminating with better connectors - there are more ScotchLok connectors and shoddy bullet connectors here than is healthy!
Since removing and replacing a few more relays, the indicators are now totally inoperable, left and right, but the short circuit is no longer present, so I've disturbed something! The only part of the harness I haven't inspected now is the section between the back of the instrument panel and the interior fuse box. The next day or so should take care of that.
Thanks again guys for all the suggestions - all helpful.
Neil
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wrote:

Well guys thanks again for all the suggestions.
I think I've sorted it! Since last update, I have re-terminated just about every connector in the indicator wiring. I have found several suspected high resistance connections in the left indicator wiring towards the rear.
The excessively high current was being drawn by the flasher unit itself but only sometimes, and only ever when indicating Left. The indicator lamps themselves continued to function momentarily under fault condition, hence not a wiring short circuit. The flasher unit appears undamaged in any way but eventually failed completely.(I may dismantle it and see inside when I have a little more time).
I am still puzzled at how the operation of the left indicator switch or even cross connection at the multiway connector without the switch, caused the fault condition.
The heated rear windscreen circuit was faulty in 2 places. The feed to the element was loose/disconnected behind the internal panel at the back of the rear off-side tail light. There was also a loose/high resistance connection in a multiway connector in the engine bay. I also found one of the fusible links slightly corroded and loose, which may have produced an excessive voltage drop under high current conditions.
So fingers crossed - all appears to be working as it should.
Neil
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snipped-for-privacy@thisaddy.com says...

Nice work Sir.
Dave B.
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Could try bypassing the indicator relay so the indicators are on all the time, use a headlight bulb (both filaments) as a fuse then try wiggling the wires everywhere till the bulb glows bright, when it does there's your short. Worth a try. -- Jon
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