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Parasitic Current
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General_Git
 


Member Since: 20 Jun 2019
Location: Reading
Posts: 114

England 2005 Discovery 3 TDV6 HSE Auto Zambezi SilverDiscovery 3
Parasitic Current

Give me a broken diff or turbo to change, these sorts of jobs drive me potty. Wonder what you will make of this.

Flat battery! Happened only last week too so needs to be investigated. Steady state parasitic current is around 5 A so clearly high. Started pulling fuses and discovered around 4.5 A on Fuse FL18 and 0.5 A on FL15 (engine bay). Referring to trusty ol' Haynes reveals both of these are for the heated front screen (curiously Haynes gives them as a different rating to what I discovered - important for later).

Well there we are I thought. I can live without a heated front screen so I'll leave the fuses pulled. I'll charge the battery up and we're home for tea and medals and I'll look at the front screen later - maybe...Smile

Of course not!!!

With the two fuses pulled the following behaviour was observed. Electric windows and radio inoperative. indicators flashed at 2 Hz suggesting a bulb blown. HDC and suspension faults flashing on the dash and unable to remove ignition key. This doesn't sound much like the heated front screen so I'm confused and not really sure what I want to do next.

I haven't connected my IID yet but the battery is on charge overnight so I'll be doing that first thing and posting the results. Hopefully, they will point at the culprit so I know what to do next but if anyone has any thoughts on this I'd be pleased to read them.

Update tomorrow... LR3 MY05 TDV6 2.7 HSE - 130k
Audi S3 Black Edition Quattro (2020) - 11k
ZZR1400 (2010) - 55k  
Post #234625127th Aug 2023 7:58 pm
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Pete K
 


Member Since: 15 Jan 2016
Location: GL
Posts: 10679

England 2005 Discovery 3 TDV6 HSE Auto Rimini RedDiscovery 3

I thought FL18 (from memory) was a fuse that power most things in the cjb (glovebox fuse box)  
Post #234625427th Aug 2023 8:14 pm
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Pete K
 


Member Since: 15 Jan 2016
Location: GL
Posts: 10679

England 2005 Discovery 3 TDV6 HSE Auto Rimini RedDiscovery 3

https://www.disco3.co.uk/forum/topic167874-90.html

If you go down the page above you will see all the internal fuses and functions powered off FL18
Time to pull them fuses behind glovebox.
Or measure the milli volts across the fuses to see which one is drawing current  
Post #234625627th Aug 2023 8:20 pm
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General_Git
 


Member Since: 20 Jun 2019
Location: Reading
Posts: 114

England 2005 Discovery 3 TDV6 HSE Auto Zambezi SilverDiscovery 3

alrighty!!

F53 and F52 seem to be the culprits and now the parasitic current is less than 50 mA. Battery charged and car appears to be just fine except for the obvious problem of no tunes and no satnav screen.

I've got the HK sound system and a GVIF with two headrest screens which I assume are on the same circuit so the problem must be somewhere around here.

Step 1: Look for something obvious around the GVIF and seats - 5 A at 12 V is 60 W, which will burn and give off a smell so I might be able to find it that way.

Step 2: unplug head unit to see if current reduces.

Other than this, I'm not really sure how to approach the problem so I'd appreciate any help... LR3 MY05 TDV6 2.7 HSE - 130k
Audi S3 Black Edition Quattro (2020) - 11k
ZZR1400 (2010) - 55k  
Post #234644529th Aug 2023 9:40 pm
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Brian Considine
 


Member Since: 05 Dec 2022
Location: Nr Margate
Posts: 280

United Kingdom 

if you do not have to reset anything after removing F52 & F53 then you could wire a couple of ignition fed relay's into their circuits.

I ended up doing something similar to my L322 to the interior lighting circuit. Bit of a pain only having interior lights with the key in the ignition but better than flat batteries.  
Post #234648930th Aug 2023 9:39 am
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Pete K
 


Member Since: 15 Jan 2016
Location: GL
Posts: 10679

England 2005 Discovery 3 TDV6 HSE Auto Rimini RedDiscovery 3

So when the headunit is activated, (that is the moment you press unlock on the key, until the radio display is blank (no clock displayed)) it activates a relay inside the CJB, (passenger fusebox). The relay then powers those 2 fuses.

So it could be:

1) check when you are doing the measurements that the headunit has shut off, and not displaying the clock. The CD drive will usually make a noise after 3 minutes? of being told to shut down. Turn it on and then off. Wait 3 mins

2) The headunit maybe commanding the relay on. Unpluging it would prove it.
3) The relay is stuck closed in the CJB.  
Post #234650130th Aug 2023 11:29 am
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