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| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 17388   
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You are very likely to destroy the alternator if you do this, since it will try very hard to charge the battery that isn't there.
In general a vehicle with an alternator, unless it is a machine-sensed type, must not be run without a battery connected. Quite apart from that, if you could do this safely the alarm will still sound since it will now be powered from the alternator rather than the battery. Do you have a battery-backed sounder, or is it just the standard alarm sounder that it activating? If it is just the standard one, why not just disconnect the sounder? Alternatively you probably could remove the drive belt so that the alternator isn't running, jury rig a 12v supply to the fuel solenoid independently from everything else, then bump or tow start the vehicle. That should work. |
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2nd Jan 2021 12:07am |
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| hxk494 Member Since: 29 Apr 2013 Location: Edinburgh Posts: 239
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thanks for your thoughts Blackwolf. I had presumed disconnecting when runing might not be the best idea for the alternator but good to get confirmation.
I believe that it's a standard factory 1996 alarm/immobiliser and I don't think there's a BBUS, so disconnecting the sounder is what I'm aiming to do - it's just that it seems to be buried out of sight in the nearside wing and to sensibly reach it I'm going to have to do some dismantling - hence the desire to get it inside if I can as it's sub zero here with snow on the ground and more falling as I write! Taking off the drive belt and rigging 12v to the stop solenoid was another option i had considered - presumably starting it from the vehicle batterty then disconnecting it without the alternator in the loop wouldn't bring the same problems as disconnecting when alternator is producing power? 1996 300Tdi Defender 110 |
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2nd Jan 2021 9:15am |
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| Dinnu Member Since: 24 Dec 2019 Location: Lija Posts: 3414  
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Probably you already know it, without the aux belt the water pump will not be running, so only to be done for a very short period so as not to have a very hot head with a very cold block.
Alternatively disconnect the connector/wiring from the alternator? 1988 90 Hard Top, 19J Diesel Turbo, Shire Blue - Restoration ongoing 2012 90 CSW, 2.2TDCI, Santorini Black |
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2nd Jan 2021 9:26am |
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| hxk494 Member Since: 29 Apr 2013 Location: Edinburgh Posts: 239
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thanks Dinnu, yes was aware of that, no water pump or power steering so as you say, only for a very short time. 1996 300Tdi Defender 110
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2nd Jan 2021 9:47am |
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| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 17388
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Disconnecting the plug from the alternator will not guarantee that the alternator survives, it depends on whether or not it self-excites (if it does, it is likely to be destroyed).
If no BBUS, the sounder is likely to be a thing that looks like a horn or buzzer unit and is probably accessible if you look from the engine compartment down towards the back of the n/s headlamp in the n/s wing. It may be possible to reach it by sticking your arm down the same route, if not you will need to take the n/s headlamp out. |
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2nd Jan 2021 10:40am |
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| Dinnu Member Since: 24 Dec 2019 Location: Lija Posts: 3414
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Blackwolf has a point there if the alternator is self exciting. I assumed that removing the excitation will not harm it if it spins. 1988 90 Hard Top, 19J Diesel Turbo, Shire Blue - Restoration ongoing
2012 90 CSW, 2.2TDCI, Santorini Black |
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2nd Jan 2021 4:16pm |
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| dailysleaze Member Since: 23 May 2013 Location: United Kingdom Posts: 237
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A passenger of mine once kicked out the battery cut off switch whilst driving which stopped the engine and fried the stereo
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2nd Jan 2021 7:27pm |
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