Disco 1 Courtesy lights flickering....

Hi All,

So, 1997 D1 300Tdi Auto 5 door.

Courtesy lights flickering, all the time (whilst they are switched on) They do not switch orft with either the alarm ( fob or key ), or after starting engine. Ignition barrel indicator lamp - also lit all the time...

"Key in" bleeper works properly - "on" when drivers door is open, and orft when it is shut.

MFU appears fine in other functions, except the HRW - the 30A fuse under the bonnet has gone, and blew another when replaced....

Haven't yet managed to get the MFU into test mode - presume due it thinking a door is open !

Thus, I think I am looking for a short somewhere ...

Measured the voltages on the door switches with the battery at 13.7 ( on charge) :-

Drivers 12.28 - NSF passenger - 12,28

Both rear passenger doors at 12.18

Rear door at 11.2 ....

Might tie in with the HRW issue ?

Any and all assistance gratefully received - and if anyone has some colour wiring diagrams, that would be super useful.... RAVE seems to indicate a joint the main front to rear loom - but I am reluctant to take the headlining out if I can avoid it

Cheers.

The interior light flicking has been mentioned before in Forums over the years, I believe it’s because of a fault with the MFU and is resolved by replacing the unit, there have been the usual earth/fuse suggestions, but no one has given the definitive answer... as far as I've seen.

So u have proved there’s wiring continuity between the MFU and the door pins, just checking that the interior lights illuminated when opening the door would also have told u that.

If the MFU is failing the u may have issues with one or more of the other circuits the unit is involved with, the inbuilt diagnostic procedure is in RAVE, also its been posted in the forum, unable to start the test is an indication of a faulty unit.
You could instead do a visual check, does the wiper delay function, head lamp washer, rear fog lights operate correctly & the heated screens time out, etc etc?

I had to replace my MFU eleven years ago, the whole unit failed due to me overloading it, so nothing worked, it cost me £133 back then from Rimmer bros. If yours is original its done well.

discool said:

just checking that the interior lights illuminated when opening the door would also have told u that.

Click to expand...

Yeah, but no but .... They don't - they flicker all the time .... the test was to try to find the earth fault, if any - I.E. if one door tested at a very low voltage, then .....

No issues, as yet with any of the other circuits - which is why I was thinking / hoping for a wiring / earth fault

discool said:

If yours is original its done well.

Click to expand...

It's a 97 vintage one, so, yep, it has done well .... they are now about £230 - and I've ordered one - should be here monday, courier permitting

Disco1BFG said:

Yeah, but no but .... They don't - they flicker all the time .... the test was to try to find the earth fault, if any - I.E. if one door tested at a very low voltage, then .....

No issues, as yet with any of the other circuits - which is why I was thinking / hoping for a wiring / earth fault



It's a 97 vintage one, so, yep, it has done well .... they are now about £230 - and I've ordered one - should be here monday, courier permitting

Click to expand...

I’d expect the 12v supply from the MFU to the lights would be fluctuating in time with the flickering,
So the link from the MFU to the door pins is proved to be OK although when a door is opened the lights flicker.
Thinking back, it’s possible that my interior lights were flickering along with everything else that the MFU controlled being dead.
I didn’t pay to much attention as it was a very cold December evening with deep snow when when the unit failed, so went in straight away and ordered a replacement unit.

discool said:

So the link from the MFU to the door pins is proved to be OK although when a door is opened the lights flicker

Click to expand...

Just to be awkward, and quite unique ...... they flicker all the time - door open or closed makes no difference - hence me thinking of, and looking for a short in the wiring - which I haven't found ( cos it ain't there )

I blame the prince of darkness - I mean, it's only lasted 23 years - how rude Wonder if I'll get anywhere with a warranty claim

Be nice if the new one lasts another 23 years !!

So, still struggling here .

New MFU came, and was fitted - all working, but not for long . No courtesy lights, no HRW no rear fogs etc.

So, put the old one back in - back to as post #1.

Took the front courtesy light out - which stayed lit, despite separating the earth, given it comes apart in two pieces - it also has two wires to the bulb half, and an earth wire to the backing plate

Anyone care to help me with this please... @sierrafery .... @mystery

TIA.

Disco1BFG said:

So, still struggling here .

New MFU came, and was fitted - all working, but not for long . No courtesy lights, no HRW no rear fogs etc.

So, put the old one back in - back to as post #1.

Took the front courtesy light out - which stayed lit, despite separating the earth, given it comes apart in two pieces - it also has two wires to the bulb half, and an earth wire to the backing plate

Anyone care to help me with this please... @sierrafery .... @mystery

TIA.

Click to expand...

I wouldn’t expect a brand new MFU to be faulty.
Did you prove that your existing MFU was faulty?
Bridging the purple/blue wire locally to the interior lamp earth connection (the boot doesn’t have an earth) and with the bulb in place it should have illuminated continuously, the purple/blue wire is just the link to the MFU, which when functioning will provided the ground for the circuit, the the simple ‘bridge’ overlay bypasses that wire.
U have proved the continuity to the door pins and 12v supply from the fuse as ok, there’s nothing left i can think of.

discool said:

I wouldn’t expect a brand new MFU to be faulty.

Click to expand...

Agreed, and thanks for your continued help .

discool said:

Did you prove that your existing MFU was faulty?

Click to expand...

I tried to prove the existing MFU faulty - but it will not enter self test using the published procedure... I disconnected and insulated all the door switch wires, and the courtesy lights stay on....

The new MFU worked perfectly, until I put everything back together - I.E. OSR jump seat back in - it was out to check the 12S wiring - which was a mess, and which I tidied up.

Now, with the new MFU, I have no functions at all (!) - with the old one, nothing has changed from post #1.

discool said:

Bridging the purple/blue wire locally to the interior lamp earth connection (the boot doesn’t have an earth) and with the bulb in place it should have illuminated continuously, the purple/blue wire is just the link to the MFU, which when functioning will provided the ground for the circuit, the the simple ‘bridge’ overlay bypasses that wire.

Click to expand...

They are already on continuously ! the little bar stewards ! - The more I look, the more I think this is a wiring fault of some sort.

discool said:

U have proved the continuity to the door pins and 12v supply from the fuse as ok, there’s nothing left i can think of.

Click to expand...

I took the NSR speaker and associated panels out to try and locate a joint mentioned in RAVE - found it, and it appears it is vehicle lighting only.... However - whilst moving the loom, I notice the "boot" courtesy light flicker - and more agitated movement produces lots of flicker - on examination, there is some damage to the tape wrapping of the loom - so I'm going to split the loom, and see if I can find the cause.

I note from @Jasonmichael 's thread here:-

https://www.landyzone.co.uk/land-rover/electrical-gremlins.298697/

That the alarm/immobiliser can cause issues too .... - so I might have a look at this too...

At the moment, I'm pretty convinced it's a wiring issue - probably in the loom over the rear door, or thereabouts.

What Excellent memory U have on the 4year thread(link).

Well the MFU has an input from security ECU, so if this is faulty, I believe it can suffer from iffy terminals or joints, it may be possible to be DIY repaired, if replaced, the ECU then you need to the matching fob/s, to save money remote key can provide fobs @ £70 + each.

Hello Disco1BFG,

Did you ever solve you're flickering light problem???

I'm sorry, I know you added me in to the post but unfortunately COVID struck me down & I've been hospitalised 3 times & the 3rd time due to a Pulmonary Embolism caused by COVID!!!

I did eventually get to the bottom of my problem after faffing around for a long time & (wrongly) trusting an auto electrician to diagnose my problem saying it was a faulty Alarm ECU.
I sent the alarm ECU off to a guy who repairs them, he looked at it, tested it and said there was nothing wrong with it and sent it back to me in the post. So (and this is a long time ago now so bear with me. I traced all the wiring (which took an absolute age) for the door switches and loosely rewired each one in turn (not tidily, had wire all over the car). All 4 doors were tested one by one and all ended up with the same result = interior lights STILL FLICKERING Then I did the one for the boot, HEY PRESTO!!!!!! When all reconnected up again the interior lights BEHAVED themselves!!!! I can only think that somewhere along the wiring there was either a chaffed wire or bad earth, or something somehow was interfering with the HRW & the rear boot door wiring causing the problem. I ended up replacing the full wire for the boot door & splicing it into the passenger door / tailgate input.

@Jasonmichael - Thanks for the reply - really sorry to hear about your health issues - 'specially the embolism - they can be really bad

I've had an aneursym let go, so I have some idea of the mess such a thing can create... Wouldn't wish it on anyone....

Hope you are the right side of it all now

I found the issue with my courtesy lights is that the MOSFET which grounds them is getting a permanent 3.6V gate signal - thus they are always grounded. I also found a load of verdigris in the connector for the light above the rear seats - and this was caused by the rear sunroof drains being squashed by the interior of the car - and an unwholly rotten mess has been created...

So, after removing rust from the inside of the roof , and replacing the headlining .... I'm still of the opinion that there is an issue in the main loom in front of the dash / behind the bulkhead. To say this has been expensive is something of an understatement ..... I'm still considering my options

The guy who tested your alarm sounds a useful contact - any chance of his details ?

I'm glad you got to the bottom of your issue - I haven't, yet....

Disco1BFG

The website for the alarm test / repair is https://www.technozen-electronics.co.uk/land-rover-10as-alarm-ecu-services/

Hope you get sorted soon!