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redline

Member Since: 28 Jun 2015
Location: Mountains and Lakes
Posts: 221

Self inflicted electrical problem

===============================================================
SOLVED

Synopsis: Short circuit on interior lights. Vehicle would not start / immobilized.
Main Symptoms: No power to starter relay. When activated manually, car would crank but not start.
Faults: Lucas 10AS immobilizer was not getting power.
Solution: Fuses F8 and F30 had blown. Also check Fuse F15. All in main junction box.

===============================================================

Ok, hopefully a trivial problem, and I can find a resolution here, before I cause more trouble fiddling with the electrics…

So, I was replacing the rear internal light in my Defender with a MudStuff LED unit (one of these: [url]https://www.mudstuff.co.uk/mud-led-interior-lamp.html [/url]- which are brilliant by the way!). It’s “supposed” to be idiot proof, as unit is plug-and-play with colour coded wires. As I was removing one of the nuts, I managed to touch the spanner on one end of the bulb. Unfortunately the stud is on a plate behind the roof-lining, to which the light is earthed…. so instant short … and both interior lights went off. No problem I thought – just a fuse.

So after I finished installing the light, I opened the main fusebox under the steering wheel, to find the offending item. From the symbols, it wasn’t obvious which one it was. So I firstly pulled F20 (10A Illumination/clock) but it was ok. I then pulled F15 (5A Ignition)… at which point the dashboard went dark. The fuse was ok, so I replaced it, and the dashboard lights went back on with a beep. Trip meter was now at 0km. I looked at a few more fuses, and then though I better check online. At which point I went to start the car, to put it back in the garage…. And it was completely dead – meaning it didn’t crank. I pulled the F15 fuse again – dash lights went off, and on again with a beep when the fuse is replaced. Unsurprisingly, car still didn't start.

So the questions for you smart folks on here are:
1. What is going on with the ignition? I am assuming that it is related to me pulling the fuse rather than the shorting the interior lights?
2. Which fuse are the interior lights on, and what else is on that fuse?

Hopefully I haven't done anything too dramatic- like kill the ECU - over a two penny fuse

NB - Car does not have an immobiliser.

Last edited by redline on 11th Dec 2018 9:20am. Edited 3 times in total

4th Dec 2018 4:40pm

Martin
Site Admin

Member Since: 02 Apr 2007
Location: Hook Norton
Posts: 6605

2015 Defender 90 Puma 2.2 XS CSW Montalcino Red

You have blown the fuse for the immobiliser unit, which is still fitted although you don't have the fob - it controls the interior lights too. I don't know which fuse number it is without referring to the diagrams and I don't have access to them right now (sorry)

1988 90 Td5 NAS soft top

2015 D90 XS SW

4th Dec 2018 4:56pm

dorsetsmith

Member Since: 30 Oct 2011
Location: South West
Posts: 4554

interior lights fuse ( 2.4 ) fuse 30

interior lights fuse (2.2 ) fuse 29P both 10 amp

4th Dec 2018 5:08pm

redline

Member Since: 28 Jun 2015
Location: Mountains and Lakes
Posts: 221

Many thanks Martin for the quick reply! So, unexpectedly it was my cack-handedness with the spanner that's at the root of the problem?! Thankfully it sounds like its just a matter of locating the right fuse then...

For reference, attached is the list of fuses in the main box. The immobiliser could be F8 (indicated Alarm on the list), or F6 / F7 in the secondary fuse box (also indicated as Alarm). If anyone know for sure...

PS - I love this forum. Got a reply / solution within 15mins of posting. Absolutely awesome!

Click image to enlarge

4th Dec 2018 5:09pm

redline

Member Since: 28 Jun 2015
Location: Mountains and Lakes
Posts: 221

Thanks Dorset - I will check that right away. I should have checked the stereo (also on that fuse I believe) - would have been a give-away.

4th Dec 2018 5:11pm

Martin
Site Admin

Member Since: 02 Apr 2007
Location: Hook Norton
Posts: 6605

2.2 or 2.4?

Check fuses 6, 7 on a 2.4 or 9 on a 2.2

1988 90 Td5 NAS soft top

2015 D90 XS SW

4th Dec 2018 6:44pm

redline

Member Since: 28 Jun 2015
Location: Mountains and Lakes
Posts: 221

Car is a 2.4 ... I checked the fuses: F30 (10A) had blown. F6 and F7 in the secondary box were OK.

I changed the blown fuse, and sure enough the interior lights, dash, clock and radio started working.
However... there is still no cranking!! Everything else seems to be OK, just that nothing at all happens when I turn the key to start...

Unfortunately I didn't have time to check further, as I had to go out, so will further investigate in the morning.
From my limited understanding of electrics, the symptoms point to a relay or ignition switch issue, but I am struggling to connect those possibilities to my previous actions of shorting the internal lights and pulling a few fuses...

Any ideas / insights are - as always - much appreciated!

4th Dec 2018 9:48pm

BenB8man

Member Since: 22 Mar 2017
Location: Norfolk
Posts: 429

2010 Defender 110 Puma 2.4 DCPU Stornoway Grey

Might be thinking a little outside the box here, but following from Martins point with the immobiliser fuse blowing, as that's what tells the lights to come on. Have you tried locking and unlocking with the keyfob? Does that work ok? When you switch the ignition on do you get the usual lights on the dash? I'm guessing it's just the starter that's not turning on the final stage of turning the key on.

4th Dec 2018 11:03pm

redline

Member Since: 28 Jun 2015
Location: Mountains and Lakes
Posts: 221

BenB8man - yup, that is correct - everything seems to be working fine, except the starting on the final turn of the key.

This morning I managed to check the relays:
Both Main and Starter relays don't seem* to be working, but intriguingly the fault is on the Load Switch side, not the Coil side.
That is - when I energize the relays, I can hear the clicking, but if I measure the continuity across the switching side, it stays at 1 - so the switch isn't closing...

Increasingly confused about this....

* was a quick test - needs to be repeated more thoroughly this afternoon to be sure.

5th Dec 2018 12:36pm

Martin
Site Admin

Member Since: 02 Apr 2007
Location: Hook Norton
Posts: 6605

The immobiliser controls the earth path for the starter relay coil. I still think this is your cause.

1988 90 Td5 NAS soft top

2015 D90 XS SW

5th Dec 2018 12:37pm

redline

Member Since: 28 Jun 2015
Location: Mountains and Lakes
Posts: 221

Thanks Martin - very useful insight, as I thought the Puma 2.4 immobilizer will allow the car to crank, but not start?! If the immobilizer acts on the starter relay, then one presumes it could well be the cause of my issue ... except that my car is not equipped with an immobiliser (no key fob, and "dumb" key to start)...

5th Dec 2018 12:54pm

redline

Member Since: 28 Jun 2015
Location: Mountains and Lakes
Posts: 221

Great - tested the Starter and Main relays again, with the help of an extra set of hands to hold the leads in place - and they are both fine.

Back to square one

5th Dec 2018 1:03pm

dorsetsmith

Member Since: 30 Oct 2011
Location: South West
Posts: 4554

2.4 Puma TDCi ECM controls the earth path for the starter relay coil (VIN date specific )

Last edited by dorsetsmith on 5th Dec 2018 9:25pm. Edited 1 time in total

5th Dec 2018 1:21pm

Martin
Site Admin

Member Since: 02 Apr 2007
Location: Hook Norton
Posts: 6605

2.4:

Click image to enlarge

The 2.2 is indeed handled by the engine ECU.

@redline is your instrument pack working ok - mileage displaying ok and gauges/lights working when you turn the key on?

1988 90 Td5 NAS soft top

2015 D90 XS SW

5th Dec 2018 1:46pm

redline

Member Since: 28 Jun 2015
Location: Mountains and Lakes
Posts: 221

Martin - yup everything seems normal on the instrument cluster. Trip meter went to zero, but that is all. All other electrics
- radio, windows, dash, interior lights, etc... are working fine.

Just checked for fault ECU codes with a basic OBCD scantool, and it shows none...

5th Dec 2018 1:58pm

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