Safe to ground audio amp off tailgate door frame?

Hello.

I'm at the end of a project installing an amplifier into my rear tailgate door card to power 'a few' speakers bolted onto the door card in a custom rack I designed.

The task is nearly complete, but I just remembered as I was going to buy an 'amp wiring kit' that the distance from the amp (outside the car) to the chassis of the vehicle (inside) is over the recommend spec of 18 inches (1.5ft).

It seems I'll now have to ground the amp into the metal frame of the tailgate door, not the chassis in the car, as the swing out Freelander door, isn't the chassis as its connected by two door hinges.

The only compromise I can think of, is to run thicker 4AWG cables instead of 8AWG from the amp to a distribution block (in the boot), then 0 AWG to the battery, as I believe the thicker the gauge cable, the less it matters if the ground cable isn't a short run to the amp, and this should overcome the problem of resistance of a long ground cable.

Could someone kindly tell me if this is correct I have two options?

1) Ground the amp in a short run into the metal frame of the Freelander tailgate door
or
2) Use 4AWG long run into the boot, then upgrade to 0AWG to the battery.

Thanks for any input.

I would do option 2, slightly modified.

If you ground to the door the only conductive path to the battery is through the hinges (as you say), and I doubt that's sufficient for an amp. (Unless there's a ground strap already but still I doubt it will be enough).

Run the ground cable through the door (you may have to drill new holes in the door and shut panel) to the boot then bolt to a suitable ground point. No need to go all the way to the battery, the chassis/body will do that for you.

Nearest earths are on rear quarters either side. Probably not fit for purpose, due to age and degradation.
Do Option 2.
Mike

Out of curiosity, what amp are you running. Very few amps require 0 Gauge cables. 8 AWG is fine for cheap Chinese amps and 4 AWG for decent American amps. If 0 AWG is needed due to current requirements. It's actually better to fit a second battery in the rear and fit a charge controller to keep it topped up. Oh and run a ground wire past the hinges, onto the binding post in the rear quarter.

Nodge68 said:

Out of curiosity, what amp are you running. Very few amps require 0 Gauge cables. 8 AWG is fine for cheap Chinese amps and 4 AWG for decent American amps. If 0 AWG is needed due to current requirements. It's actually better to fit a second battery in the rear and fit a charge controller to keep it topped up. Oh and run a ground wire past the hinges, onto the binding post in the rear quarter.

Click to expand...

Hi, thank you for your reply and suggestions.

Amp:
I'm running an 'old skool' Pioneer-GMX 924 in the tailgate door card, or will be.
http://www.pioneerelectronics.com/PUSA/Car/Amplifiers/GM-X924

I realise it's old (1998) and under-powered, but I wanted to use it up as it's been in storage since I got it and I never got to use it hence I had a silly idea of squeezing it into a rear tailgate door card, door bin to 'use it up'. I've also made a few 'things' up front (speaker pods) which I will show everyone in due course, mainly as an eccentric project and also for fun to inspire others to turn their bedrooms into garages with all the cables and parts you need to assemble!

It may never work, as the considerable weight of the MDF speaker rack could snap the top of the tailgate door card off due to it's immense weight (18mm MDF with 4 speakers). We shall see, I hope it works though. I can't glue it in place, as if the amps fuses blow or the amp breaks completely, I'd have to rip the MDF speaker rack off which would break the Landrover door card (part of the amp is concealed by the MDF speaker rack, hence to remove the amp,you need to remove the MDF speaker rack. So it's a bit of a precarious project to be honest.

Battery charger/monitor:
I was thinking of using this device, although I have no idea how to fit them.
http://www.nationalluna.com/dualmon.htm

For a battery I think I'd have to buy an Optima audio battery or preferably a waterproof battery box and put it in a custom MDF/Plastic container, although really that is a summer job. National Luna also do this set up for batteries which might be good, but again, I have no clue about electricity. and safety
http://www.nationalluna.com/PPPack.htm

The main problem I've learnt doing these jobs is when it comes to the electrics it's impossible to find someone locallywho knows about audio/split charge systems in a Freelander MK1, as naturally, 4X4 type people don't usually blow 2 grand on car audio when going off-road etc and spend money on mechanics and car audio places don't know anything about 4x4's either.

Hence I get a bit lost and never finish these projects but still enjoy making them.

Skinny Mike said:

Nearest earths are on rear quarters either side. Probably not fit for purpose, due to age and degradation.
Do Option 2.
Mike

Click to expand...

Hello Mike, thank you for your help. My car certainly has the free Landrover water feature in the boot, which was also on the ceiling (rust!). As water and electricity don't mix I've never gotten around to installing car audio but as the car interior has been remove for 3 years, I finally got around to trying to re-assemble it all, but then realised my knowledge of electricity is terrible, as it is with water proofing!

To make you laugh when it rains, I have to point the car downhill (rear facing more downhill that front), so the water doesn't come in from outside (somewhere) into the boot based cubby hole thing, this is where I plan to put the audio battery! If i park the car on a level surface then the water comes in a good two inches in the boot after a few days.

As you can see, having an idea of adding tonnes of speakers to the vehicle probably wasn't the best of ideas!

NeedleNose said:

I would do option 2, slightly modified.

If you ground to the door the only conductive path to the battery is through the hinges (as you say), and I doubt that's sufficient for an amp. (Unless there's a ground strap already but still I doubt it will be enough).

Run the ground cable through the door (you may have to drill new holes in the door and shut panel) to the boot then bolt to a suitable ground point. No need to go all the way to the battery, the chassis/body will do that for you.

Click to expand...

Hi NeedleNose (cool name BTW), thank you for replying and now other people have kindly joined in the thread too. I am very grateful, thank you, as I am stuck in a 'project' and have speakers strapped to a bulky MDF board in my bedroom (with four door cards!) all waiting to be put back in, but first I need to do the electrics.

It's a good job I'm not married, I don't think anyone would like to wake up to speakers and cables in your face rather than a pillow (my current fetish!).

You don't need 0 AWG for that old school amp. It'll pull 30 Amps tops. 8 AWG will be fine but 4 AWG will give you some scope for later additional power

The towing relay is in the rear quarter passenger side. You could use that wiring for the split charge, earth included. Just buy a decent 7 way unit, not cheap crap, visit a caravan shop or car audio specialist to get one.
If @Nodge68 says you don't need to go over the top on the earth, then the towing electrics will do fine.
Mike

Skinny Mike said:

If @Nodge68 says you don't need to go over the top on the earth, then the towing electrics will do fine.
Mike

Click to expand...

Just don't crank the amp up while towing !

GrumpyGel said:

Just don't crank the amp up while towing !

Click to expand...

Or drill a hole straight down to that lovely sub frame and add another earth. Then crank it way up.
Mike

Skinny Mike said:

The towing relay is in the rear quarter passenger side. You could use that wiring for the split charge, earth included. Just buy a decent 7 way unit, not cheap crap, visit a caravan shop or car audio specialist to get one.
If @Nodge68 says you don't need to go over the top on the earth, then the towing electrics will do fine.
Mike

Click to expand...

Thanks Mike. Is the towing relay behind one of the plastic side panels in the boot? I seem
to remember when I fitted the 12v 'accessory socket' (cuts into the trim panel), on the left hand side in the boot that had some bits and bobs near it, maybe that was the towing relay?

Ages ago I found in the exclusive Freelander water feature in the boot (the cubby hole/box thingy)whilst bailing out water, a lonely factory cable and LR plug that wasn't connected to anything, probably rusted to hell now and non functional, but I think this must be a plug for the towbar, or something like that. I mentioned it as I wondered if that would be of any use too? I can take a photo of it, if it helps.

Cheers.

TD4_4x4 said:

Thanks Mike. Is the towing relay behind one of the plastic side panels in the boot? I seem
to remember when I fitted the 12v 'accessory socket' (cuts into the trim panel), on the left hand side in the boot that had some bits and bobs near it, maybe that was the towing relay?

Ages ago I found in the exclusive Freelander water feature in the boot (the cubby hole/box thingy)whilst bailing out water, a lonely factory cable and LR plug that wasn't connected to anything, probably rusted to hell now and non functional, but I think this must be a plug for the towbar, or something like that. I mentioned it as I wondered if that would be of any use too? I can take a photo of it, if it helps.

Cheers.

Click to expand...

I think some models had (wiring for) a sub-woofer in the fishtank.

There's no factory fitted supplementary trailer power feed fitted to the Freelander 1. That didn't arrive until the FL2 came out. If supplementary power was needed, a cable needed to be run from the battery or fuse board.

The 4 wires in the boot cubby are, as GG said, for the sub woofer that was fitted on the top spec model.

Trailer lighting has a connection point under the RH boot panel. There are ground posts behind bothLH and RH boot panels for the lighting and additional grounds if needed.

Sorry, @Nodge68 is correct. You need to run a power line from the battery.
In my defence, I did do mine in 8 years ago and my memory isn't what it used to be. I put an inline fuse on mine for extra safety.
Mike