 | Home > Technical > Help! VCV/ ECU PROBLEM Scared I’ve bought a nail! |
 
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| steveww Member Since: 05 Jan 2022 Location: Uppingham Posts: 569   
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A pause and a think over a brew always works.
I bet a 500A fuse blowing sounds like a rifle shot! Keep going, it sounds like you're nearly there. |
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1st Jun 2023 2:34pm |
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| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 17441 
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That is rather odd!
The megafuse protects the cable from the battery to the starter and on to the alternator, and there is nothing that immediately comes to mind that could cause a load in excess of 500A to appear on that cable just because the ignition is turned on. I think I'll need a cup of tea and a think to digest this. The usual reason for the megafuse to blow (other than the hard frontal collision it is intended for) is that the cable has chafed against the vehicle structure or engine and is intermittently shorting to ground. On the Puma the engine harness in particular is notorious for chafing anywhere it contacts the engine, and it would certainly be worth checking the harness carefully for damage. The only alternator fault I could see that could blow the MF would be if there was a fault with the field coils and there was a short to ground as a result. I am pretty sure that if this was the case it would be a short to ground irrespective of the key position though. |
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1st Jun 2023 3:26pm |
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| NickMc Member Since: 01 Oct 2014 Location: Norn Iron Posts: 1628  
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Did you look at the under dash fuse box like I suggested? I have had this exact fault, you could even remove all the relays and it would still start sometimes. The chip in the 10AS was corroded water had come in around the windscreen and windscreen “hinge” footwell
 Click image to enlarge Click image to enlarge |
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1st Jun 2023 7:10pm |
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| whathaveidone Member Since: 18 May 2023 Location: Cheltenham Posts: 28 
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Hi. Yes, I did check for water ingress there, thank you. I’ll look again for sure. I woke up thinking that those lives are surely live all the time irrespective of key position? Making this even more odd! I’ve got a decent tester to measure any earth leak however I feel it will be hiding! 😂
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2nd Jun 2023 4:58am |
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| ickle Member Since: 22 Jul 2010 Location: South Vendee Posts: 1785  
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An odd thought - scrotes accessing underneath and cutting battery cables is a known attempted theft method - have you physically checked the whole length of the battery cables for damage?
Then as you've done everything else I'd change starter and alternator, not overly expensive, both a PITA to do, but if it doesn't cure the fault at least you will not have to worry about them failing for the next 100k.... HTH Keith |
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2nd Jun 2023 7:19am |
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| Clemmo Member Since: 03 Aug 2012 Location: Mile Oak Posts: 1218  
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Keith
Thread shows OP has done both the above  Make today a little better than yesterday but not so good as tomorrow....
Defender 90 HT............Pangea Green BMW X3 Msport............Carbon Black Mini Electric................Grey. (wow!) MGB Roadster……..........Vermillion 17k miles Honda Benly CD200....Maroon --------McLouis Fusio........7.4m of fun |
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2nd Jun 2023 3:56pm |
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| whathaveidone Member Since: 18 May 2023 Location: Cheltenham Posts: 28
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Thank you for more suggestions. It would appear I possibly found the fault quite quickly. The plastic housing for the mega fuse has an indentation that holds the fuse. The after market replacement fuse was much shallower than the original ford fuse. I believe contact was not being made by a real fraction of a mm due to the plastic housing. We will see! 😂 This weekend i will spend some time with my family who have only seen my feet poking out from under the defender of late. The defender will be put into regular action on Monday so fingers crossed! 😂 Have a good weekend all and thank you again. I will update next week.
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3rd Jun 2023 5:47am |
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| whathaveidone Member Since: 18 May 2023 Location: Cheltenham Posts: 28
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Morning all. Just an update after a week. Car power is great, no weirdness or loss of power so the vcv sorted this. The advice for anyone changing the vcv is to aware of cheap parts. I even had a dud denso part out of the box. Also having changed the starter motor the main fuse has stayed good. The battery light came on earlier in the week but then the car had been started over and over and conducted some short runs, so I hope this was just coincidental. I’ve driven for a week and even almost enjoyed it! Thank you all so much for your kind help. Until the next time…. 😂😬😂
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11th Jun 2023 5:01am |
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| LR90XS2011 Member Since: 05 Apr 2011 Location: bickenhill Posts: 3643 
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the 2011s are good cars hopefully it will start to behave DEFENDER 90 TDCI XS,
I hope everyone is well and your land rovers make you happy |
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11th Jun 2023 5:44am |
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| whathaveidone Member Since: 18 May 2023 Location: Cheltenham Posts: 28
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Thank you. I absolutely loved my Td5 as a daily driver 10 years ago. I’m really hoping to trust this thing more and more. Fingers crossed. Thank you.
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11th Jun 2023 6:31am |
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