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Nobby

Member Since: 09 Aug 2012
Location: Wiltshire
Posts: 444

2010 Defender 90 Puma 2.4 CSW Santorini Black

Main Fuse Blowing

Hi Everyone and Merry Christmas to you all,
I'm in need of some help, yesterday morning, first heavy frost, as expected the fuse blew on start up....
So to bring you all up to speed, dual battery system fitted, a few years now, no problems. Replaced 500amp Mega fuse with 300amp ANL.
So early this year when the frosts hit, I was away, Wife goes to start Landy and reports nothing working. As it turns out, lights, dashboard all come on, just a click on ignition. Check main battery fuse and it's blown, swap with spare and all okay. No further problems until 2 months ago and first heavy frost since the new year. Call from Wife as before, swap fuse all okay.
Ordered spares, gone to wrong address and now waiting as post office has them.
Anyway frost yesterday and I went out to start the Landy and turn ignition, let glow plug light go out turn key and try's to start but does not fire up. Turned off ignition, back on for glow plug, re did twice to allow for poor glow plug. Turn key, does not fire, try again and heard fuse blow.
Besides no spare, what is the problem, starter motor? Never a problem otherwise, rain or sun.
Tomorrow I'll use the fuse protecting second battery, Auxiliaries only and replace main battery fuse, hope it warms up. Or I can replace a few cables and fit Land Rover Mega fuse back to keep running, however there is a fault and a 500amp fuse may allow it to fire but is it masking a potentially worse fault......
No faults on the Scangauge, batteries and cables are all fitted plus tested and no signs of a short. All other vehicles fuses are okay. Going to check the voltage at glow plugs, just to rule them out. Will jack up the Landy and check connections at the starter motor.
Any help will be gratefully appreciated, if it's easier PM me and I'm happy to talk it through?
Nobby _______________________________
Puma Defender 90

28th Dec 2016 6:23pm

dorsetsmith

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

Click image to enlarge

Click image to enlarge

main fuse 400 to 500 amp work with main battery cable from the battery down to starter motor and Alt make shore you have no faults with starter motor or Alt as well as the cabling !

Glow plug are not wired though this fuse

28th Dec 2016 7:02pm

Nobby

Member Since: 09 Aug 2012
Location: Wiltshire
Posts: 444

Thanks Dorsetsmith, I thought starter motor, didn't think about the alternator. I was happy the glow plugs were a separate circuit, just the nagging issue with only an issue with the extreme cold. Left me rather confused and almost seeking a cold weather reason, hence the glow plugs on my brain.
PM'd you re fuses.
Nobby _______________________________
Puma Defender 90

28th Dec 2016 7:16pm

dorsetsmith

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

Glow plug wired to link 1 100 amp fuse drivers seat box i believe

Last edited by dorsetsmith on 28th Dec 2016 8:26pm. Edited 1 time in total

28th Dec 2016 7:43pm

LR90XS2011

Member Since: 05 Apr 2011
Location: bickenhill
Posts: 3613

2011 Defender 90 Puma 2.4 XS CSW Galway Green

am I missing something ?

the drawing shows the starter motor as 300amps hence every now and again a 300amp fuse will blow, if the factory fitted 400 amp fuse this was for a reason, surly if its cold then the voltage is down a bit and the current goes up a bit so a 300amp fuse protecting a 300 amp load will generally blow when its cold and the load goes up and the voltage down? why not go back to the standard factory 400 amp fuse? If that blows then yes you might have a problem DEFENDER 90 TDCI XS,

I hope everyone is well and your land rovers make you happy

28th Dec 2016 8:19pm

Nobby

Member Since: 09 Aug 2012
Location: Wiltshire
Posts: 444

PM'd you. _______________________________
Puma Defender 90

28th Dec 2016 8:43pm

dorsetsmith

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

you have PM

28th Dec 2016 9:15pm

Mo Murphy

Member Since: 01 Jun 2008
Location: Letchworth Garden City, Herts
Posts: 2079

1984 Defender 90 200 Tdi HT Pennine Grey

Nobby,
So let me get this straight, you replaced the 500amp fuse that Land Rover fitted with a 300 amp item and now you are wondering why it blows when you put it under pressure starting on a cold morning ?
Really ?
Mo The Land Rover 90 - Many are called, few are chosen.

28th Dec 2016 10:23pm

Nobby

Member Since: 09 Aug 2012
Location: Wiltshire
Posts: 444

Mo, for clarity, it was after advice and sound at the time, 2+ years with no issues. Maybe as the Landy gets older and parts age, tolerances change. I only found out tonight that the starter motor draws 300amps. With the cold and now things aging it doesn't now work. Lesson learnt and posted here so others may learn. Don't forget even land rover have made a few mods and fitted lower rated fuses, again something I learnt tonight.
When I set out on my merry journey of Puma ownership, I have sometimes followed advice on various items of change for the better, some of which were checked or discussed with others via this forum. However now I've come to a problem which clearly needs addressing and was a little unsure where to go hence my post.
Again others may have gone down the same path, may now taking note and filing it for the time when something similar happens.
This forum is about helping, advising and sharing.
Nobby _______________________________
Puma Defender 90

29th Dec 2016 12:09am

dorsetsmith

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

Click image to enlarge

29th Dec 2016 10:21am

Mo Murphy

Member Since: 01 Jun 2008
Location: Letchworth Garden City, Herts
Posts: 2079

Interesting nobby, is there a thread you could link to where the 300 amp fuse change is recommended, I should like to try and understand the reasoning behind the recommendation that was made to you ?
Mo The Land Rover 90 - Many are called, few are chosen.

29th Dec 2016 5:32pm

Nobby

Member Since: 09 Aug 2012
Location: Wiltshire
Posts: 444

PM'd you _______________________________
Puma Defender 90

29th Dec 2016 6:54pm

LR90XS2011

Member Since: 05 Apr 2011
Location: bickenhill
Posts: 3613

hope it is sorted mate nothing more annoying than a recurring defect DEFENDER 90 TDCI XS,

I hope everyone is well and your land rovers make you happy

29th Dec 2016 8:09pm

Nobby

Member Since: 09 Aug 2012
Location: Wiltshire
Posts: 444

Hi LR90XS2011,

All is pretty fine now

located a mega fuse holder in Swindon, fitted it this morning. Used the original 500amp mega fuse and it started as well as ever. In my case instantly

I've removed the 500 and waiting on the Postie to deliver a 400amp fuse from dorsetsmith.

I may just be the unlucky one whose 300amp fuses and a vehicle getting older couldn't cope. Hopefully anyone else who went this way has an early heads up on potential problems or are having a similar issue now and have an answer.
It is the way of the defender, live with it, tinker with it but always learning from it.

Nobby _______________________________
Puma Defender 90

29th Dec 2016 8:49pm

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