Problem with subwoofer remote wire (Alpine SWE1200)

[defender12]

So I can't seem to get my subwoofer remote wire powering up my subwoofer after installing a second Life4P0 aux battery in my Land Rover Defender (2011).

I've got a separate fuse box under my armrest where im getting my power from from the aux battery for the subwoofer. If I connect the remote wire to the same plus as my subwoofer it powers up just fine. I've got around 13.5V there.

However the remote wire coming from the headunit (Joying) is dead, less than 1V coming from the wire. Connecting it to the power wire of the radio also doesnt work. The radio works just fine though. However I can't find any 12V from the wires there. Headunit is set to AMP- ON.

After hours of messing about my last idea was to go to the factory fuse box and get an ignition live. Went to fuse 44 which is a 5A Fuse for the Radio. Checked with the voltmeter and I've got power coming through there once the ignition is on. Connected that to the remote wire and .... nothing happens. Started the engine as I thought it might be the problem - still nothing.

It seems weird to me that the power coming directly from the fuse box doesn't power up the subwoofer but going directly to the extra fuse box coming from the Life4Po works just fine. However I don't want to have to install a switch and always have to turn it on and off... problems started once I installed my second battery. I tried with two different SWE-1200 subwoofers - so that isn't the problem either.


Any ideas? This is making me crazy....

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[1aespinoza 10+ year member]

Any ideas? This is making me crazy....

It sounds as if secondary is isolated from primary. Make sure secondary is well grounded and that the fuse from the primary going to it is well seated.

 

[defender12]

Ah I was not aware that would make a difference..

That is correct: I've got the two batteries setup with a Victron DC/DC Charger/Isolator which isolate them from each other.

AGM starter with Life4Po aux. The subwoofer is now connected to the (isolated) aux battery. Only when the alternator kicks in the two batteries are connected.

So in theory connecting the subwoofer + & - back to the primary battery would solve the problem then?

But does it really make a difference if the power for the sub and the power for the remote trigger come from two different batteries? I would have thought that doesnt make any difference?

 

[1aespinoza 10+ year member]

So in theory connecting the subwoofer + & - back to the primary battery would solve the problem then?

Yes.

But does it really make a difference if the power for the sub and the power for the remote trigger come from two different batteries? I would have thought that doesnt make any difference?

Yes. A circuit must make a closed loop. The radio is on one loop so it's remote output is on that loop, while the amp is on the secondary battery loop. You can solve this by using a 5 pin SPST relay.
Pin 30 to amp's remote
Pin 87 to amp's positive
Pin 85 to amp's negative
Pin 86 to radio's remote
Good luck.

 

[defender12]

Thanks a lot, that makes sense! I still have some relays in my garage and will give it a go on the weekend!