 | Home > In Car Electronics > Supply permanent live to headunit during cranking |
 
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| custom90 Member Since: 21 Jan 2010 Location: South West, England. Posts: 20342  
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You can but you'd have to make sure you have it turned off manually or you'd get battery drain. As is it's designed to only come on with ignition, it's already got a permanent live but it's switched via ignition on. $W33T $0U7H3RN $UG4R
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1st Feb 2014 1:59pm |
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| mrd1990 Member Since: 16 Aug 2012 Location: Wales Posts: 600  
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I've been under the impression the permanent live only goes off during cranking?
If I take the key out before the screen has fully opened, it pauses for a second then folds back and all is good, if I crank before it's fully opened, it crashes. Highly frustrating as it takes around 8 to fully turn on, it delays going off by several seconds when the ignition is turned off so plenty of time for cranking. I'm wondering really, is it voltage drop that's doing it or is the permanent live cut off to help the battery start the engine? |
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1st Feb 2014 4:39pm |
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| custom90 Member Since: 21 Jan 2010 Location: South West, England. Posts: 20342
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Voltage drop, but it should carry on in its motion straight away when power is restored.
Pretty much immediate really, so it's down to the. Electronics of the HU. I know the issue your talking about, must be very frustrating! $W33T $0U7H3RN $UG4R 🇬🇧🏴🏴🏴🇮🇪🇺🇸⛽️🛢️⚙️🧰💪 |
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1st Feb 2014 5:18pm |
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| landy andy Member Since: 15 Feb 2009 Location: Ware, Herts Posts: 5693 
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Would have thought you could wire a live direct from battery that is activated by ignition live relay that has a delay so no power drop during cranking.
Andy |
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1st Feb 2014 5:21pm |
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| custom90 Member Since: 21 Jan 2010 Location: South West, England. Posts: 20342
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Shouldn't do it though anyway, with mine if it's coming out and I crank it over it stops for a split second and then carries on.
Same with the opposite if I close it down and shut the ignition and engine off at the same time immediately it'll still close with the engine and ignition completely off. $W33T $0U7H3RN $UG4R 🇬🇧🏴🏴🏴🇮🇪🇺🇸⛽️🛢️⚙️🧰💪 |
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1st Feb 2014 5:25pm |
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| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 17369 
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I think you'll find that there is already a permanent live in the standard connector, and your problem is simply that when you crank the terminal voltage is being pulled down low enough to cause the unit to drop out.
You may find that running a heavy gauge wire straight to the battery helps. You could also as a test try starting with a second vehicle (with the engine running) connected with jump leads, since it is likely that this will hold the terminal voltage up whilst cranking. |
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1st Feb 2014 7:03pm |
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| WelshGas Member Since: 01 Oct 2010 Location: Vale of Glamorgan Posts: 935 
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Has this always happened?
How old is the battery? Have you checked battery voltage at rest after a trip and first thing in the morning, before starting up? LANDYWATCH 
Neighbourhood Watch for Land Rover Owners http://www.landywatch.co.uk/smf2/index.php |
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1st Feb 2014 7:36pm |
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| mrd1990 Member Since: 16 Aug 2012 Location: Wales Posts: 600
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The battery is good, started up fine after a week standing unused in Scotland over Christmas and the problem still persists after a long trip.
This has always happened since I installed the HU. I'm convinced I've read somewhere that the live feed is cut during cranking. Voltage drop is just as likely but I want to rule out everything else first, having said that the handbook says 10.5v as the minimum operating voltage. A small second battery looks like the solution at the moment.. I will take the dash off and try some tests tomorrow if the rain holds off |
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1st Feb 2014 9:13pm |
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| dorstsmith2 Member Since: 06 Aug 2012 Location: On the third rock from the sun in dorset Posts: 188 
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https://www.defender2.net/gallery/albums/u...lock~0.JPG
this works volt drop problems sorry the pic to small will try to sore it out |
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2nd Feb 2014 8:50am |
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| dorstsmith2 Member Since: 06 Aug 2012 Location: On the third rock from the sun in dorset Posts: 188
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https://www.defender2.net/gallery/albums/u...lock~1.JPG
NO can not fix it  Last edited by dorstsmith2 on 2nd Feb 2014 9:03am. Edited 1 time in total |
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2nd Feb 2014 9:00am |
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| K9F Member Since: 12 Nov 2009 Location: Bournemouth Posts: 9610 
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I work in the marine industry and these are good and would undoubtedly suit your purpose.
http://www.boatlamps.co.uk/contents/en-uk/d191.html If you go through life with your head in the sand....all people will see is an ar5e!! Treat every day as if it is your last....one day you will be right!! |
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2nd Feb 2014 9:01am |
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| dorstsmith2 Member Since: 06 Aug 2012 Location: On the third rock from the sun in dorset Posts: 188
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Click image to enlarge see computer you will never win   |
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2nd Feb 2014 10:30am |
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| mrd1990 Member Since: 16 Aug 2012 Location: Wales Posts: 600
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So the 40v cap will give the radio priority over the starter motor?
I've read that diodes can be damaged by cranking and fail leaving battery drain? I'll build it an see what happens, struggling to find the diode, any other diodes I can use that are available on amazon?  |
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3rd Feb 2014 10:48pm |
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| K9F Member Since: 12 Nov 2009 Location: Bournemouth Posts: 9610
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Try Maplins......
If you go through life with your head in the sand....all people will see is an ar5e!!
Treat every day as if it is your last....one day you will be right!! |
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4th Feb 2014 11:13am |
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