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Inigo



Member Since: 13 Nov 2011
Location: Kent
Posts: 624

United Kingdom 2012 Defender 110 Puma 2.2 USW Orkney Grey
Remote Power Cable to Subwoofer
Following several stereo upgrade threads on here, Ive replaced my head unit and speakers and attempted to wire in a sub. The sub does not appear to be working.
When I test the power on the blue cable from the head unit, it only appears to be 6 volts.
Is this right? I shall try to piggyback off the main 12V supply to the sub to test, but wondered what the remote cable should be.
Post #115740 15th Jan 2012 8:36pm
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ken



Member Since: 18 Aug 2009
Location: Banging Birds with my bitches !!
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United Kingdom 
Blue is a switching cable A Powered (Active Sub) will need a 12V feed fused and direct from the +ve
Post #115754 15th Jan 2012 8:57pm
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ben_j85jty



Member Since: 02 Sep 2008
Location: Bicester, Oxfordshire
Posts: 491

United Kingdom 2002 Defender 110 Td5 XS DCPU Bonatti Grey
The wire may well be the switching wire for the sub.

My alpine has a Permanate +ve and -ve feed, and is turned on with a feed from the head unit. It won't take a lot of volts for the switch to activate. 2002 Defender 110 DC
Post #115762 15th Jan 2012 9:09pm
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Inigo



Member Since: 13 Nov 2011
Location: Kent
Posts: 624

United Kingdom 2012 Defender 110 Puma 2.2 USW Orkney Grey
Sorry, didn't make myself clear. I have run a permanent 12V feed direct from the battery. There is a blue cable that is the remote control feed from the head unit (pin 7 - black/blue cable on landrover original wiring). It is this cable that only seems to have 6V. I made a little Y-piece to take power from the main 12V feed permanent live that feeds the sub and also fed this to the remote power input (so it now has 12V). Sub lights up and works great, but is permanently one so will drain battery unless I fix this.

So, does anyone know what voltage the black/blue cable from the ISO connector at the back of the head unit should carry? Is this effected by my change of head unit? I'm not sure if the power supply is switched by the car or the head unit.
Post #115773 15th Jan 2012 9:30pm
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K9F



Member Since: 12 Nov 2009
Location: Bournemouth
Posts: 9610

United Kingdom 2008 Defender 90 Puma 2.4 XS CSW Stornoway Grey
It should be 12 volts! I suspect you may have a high resistance. The original head unit has two fuses #30 which is a 10 amp and fuse #44 which is 5 amp. I would suggest check the output voltage from the fuses as a start. The blue auxilliary can also be used as an electric aerial when the unit is switched on. Does the blue run through a DIN connector? I cannot remember, but if it does possibly clean the connector and check the voltage there if still only 6 volts cut the cable back and then recheck the voltage, may be a broken cable too. Hope this helps. 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!!
Post #115787 15th Jan 2012 10:11pm
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Inigo



Member Since: 13 Nov 2011
Location: Kent
Posts: 624

United Kingdom 2012 Defender 110 Puma 2.2 USW Orkney Grey
OK, helpful pointers, thanks.
Post #115793 15th Jan 2012 10:35pm
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XS Pete



Member Since: 13 Jan 2011
Location: Suffolk
Posts: 632

England 2011 Defender 90 Puma 2.4 XS CSW Stornoway Grey
I would think that the sort of resistance required here to drop the 12V down to 6V would probably blow either a 5A or 10A fuse. It's probably more likely that there's either a fault in the head unit or one or other of the fuses has already blown for some reason, allowing the remote line to float.

Pete
Post #115898 16th Jan 2012 1:00pm
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Inigo



Member Since: 13 Nov 2011
Location: Kent
Posts: 624

United Kingdom 2012 Defender 110 Puma 2.2 USW Orkney Grey
Aha, further testing explained the mystery. Like a numpty I got confused between block A and block B so had connected to one of the speaker outputs. The fluctuating 6V (that I had put down to a loose connection somehwere, or my inability to get a good connection with the test probes) was in fact the signal to the speaker.

All working wonderfully now, just got to tidy up the cables and work out a sensible way of getting the permanent 12V cable back to the sub.
Post #116589 18th Jan 2012 8:06pm
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XS Pete



Member Since: 13 Jan 2011
Location: Suffolk
Posts: 632

England 2011 Defender 90 Puma 2.4 XS CSW Stornoway Grey
That makes more sense. You can get all kinds of voltages on amplifier output terminals depending on the type and configuration. On very large PA systems such as used in large factories, these can be in excess of 100V!.

Glad it was a simple fix with no damage done.

Pete
Post #116726 19th Jan 2012 11:56am
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