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Discussion Starter · #1 ·
I will be adding a second battery with a relay isolator. I'd like to know of the locations of lines that are active only when the engine is on (not just accessory).
It seems the norm is to put the relay isolator in the engine bay, so I'm guessing I'll have to tap into something in the fuse box? Any particulars would be greatly appreciated.
If it's possible to put the relay isolator in the boot closer to the battery with no ill effects, then are there any ignition lines inside the cabin? I have the Monsoon system installed, but afaik there's only an accessory signal line involved.
 

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The 75X lug on the relay plate (behind the left lower dash panel - just 3 screws to get to it) is a feed from the ignition load-reduction relay - "Hot with ignition on (not during cranking.")
Or, do you need the thing live also when cranking?

Monson amp:
Actually, it doesn't even have a trigger wire. It's a signal-sensing thing (audio input turns the amp on.)
 

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Discussion Starter · #3 ·
Thanks for the response. I'll look into this '75x lug'.

I have a sub hooked up, it's using a trigger wire in the back there by the monsoon amp, but iirc you're right, the remote signal wire I'm using was for the disc changer.
 

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As the current comes from the front there is no advantage in fitting the relay in the back,
mount it near the front battery and connect the relay contact 30 directly to the battery +, with a fuse inline.
 

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Discussion Starter · #5 ·
I was thinking of relay in the back because it would make it a little easier to throw on a jumper across its contacts should I have a need to parallel the batteries when the car is off. But thinking about it, the chances of having to do that (basically only if starter battery gets drained) should be slim. I do have a phantom current draw problem so my car can't survive a couple of days parked, but I'll be tracking that problem down and did just set up a solar trickle charger.

Anyway, I'm thinking I might put the second battery in the rear passenger's footwell. For weight distribution (the battery is like 60lbs) and it'd be easier for my plan to run all accessory outlets to the second battery (and disconnect them from the starter battery as they are now from factory). With the battery there, putting the relay in somewhere in the engine bay does seem a better option than in the cabin.
 

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Discussion Starter · #6 ·
Alright, so relay isolator is going in the engine bay. It's smaller than I expected, about the size of a D cell.
So where do I find the 75X equivalent (ignition hot) in the engine bay?
 
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