Club 80-90 Forums

I'm trying to fit a new stereo into my LHD Westy, used what I thought were the old wires to connect stereo up. But it/they don't seem to have be right.

Is the German T25 a 12v negative earth?

Also what colour is the + and - wires?

Is the German T25 a 12v negative earth? - Yes

The - ( negative ) is brown

The speaker wires are thin pairs, of either grey or brown wires, and one wire in each pair will have a coloured stripe running down it. This coloured stripe should be considered as the speaker + (positive) wire.

There will be two live wires ( TAKE CARE HERE ) one will go on and off when you turn the ignition on and off, and one will stay live all the time.
My preference is not to use the one that goes on and off with the key, but to use the one that stays live.

Without looking at my van I cannot remember what colour it is.
Use a bulb earthed to a bare bit of metal to check. (this is a better way of doing it than even using a proper test meter for the home radio fitter by the way, won't bore you with why !! )

Tip 1 = Always wire the live wire up LAST

Tip 2 = Be very carefull when messing with the live wires, they are not dangerous to you, but a simple, easily made slip and you can blow a fuse, then spend 10 minutes finding which one, etc, very annoying. Or, it can touch on a wire comming from the stereo and instantly wreck it.

Tip 3 = First test to be done at a LOW volume, if you don't here sound comming from it at low volume DON'T crank it up ( it's an instinct to do that !! ) if there is summat wrong with your speaker wiring and you crank it up you will blow the output chip = expensive repair.

Take care with that live wire when it is hanging loose from the dash, they always head striaght for the worst place to short against !!

Oh and remember the radio will have two wires that need to be live.
One is for the main power ( sometimes connected to the one that goes on and off with the ignition so the radio goes off when you take the key out (perhaps not desirable in a camper van)

And one that feeds the radio station memory chip, this needs to stay live all the time.

Another wire comming from the radio (usually yellow) comes live when you turn the radio on ( this is for electric aerials etc ) take care this wire, if not used, is insulated with tape or a "chocky block connector"

Bore me with why, I'm interested!

Not meaning to threadjack or anything but there has been some talk about not using the vehicle wiring for powering modern head units as it just isn't up to it. If I were to run power all the way from my battery, given that my battery is at the back instead of under the seat, what weight of wire should I use?

I have 1mm tri rated, I have lots of 2 core ac flex, would either of these be sufficient or should I buy something beefier? I would work it out but helpfully sony have not included any figures for how much power the head unit will draw.

Re the boring bulb test bit.

Some wires can "appear" to be live when tested by a meter, but as the meter does not put any load on the wire, it can give a false reading.

The wire might not be comming directly from it's appropriate fuse, but instead, be going via another piece of equipment.

By testing it with a bulb, earthed to a clean bit of bare metal on the body, you are putting it under load, and the bulb will only glow brightly if the wire is a genuine live feed.

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Re wire size

OK - firstly if you like playing rave or reggae, loud, on a powerful system, then no the wire is not up to it.

But for "normal" use it is fine.

This is not really a safety issue by the way, it is more that during very loud bass passages in the music, such as a reggae beat or rave drum and bass sounds, the wire cannot pass enough current to produce the volume, and the bass gets distorted. (btw, this in turn distorts the other ranges due to a thing called "modulation", but that is even more boring ( tho I can if you want )

In my opinion, if you are not using any external amps, then the supplied wiring is fine.

Look at the thickness of the main + wire comming out of the radio and consider that as OK ( the radio manufacturer did ! ).

More detail =

The power ( measured in Amps ) that must go down the cable roughly equals the TOTAL power output in Watts, divided by the Volts ( 12 ) then mutiplied by 1.5.

Therfore a 100 watt stereo will use 12.5 Amps MAXIMUM.

The problem is that nowadays manufacturers tell lies about the power output of their stereos to sell them.

If it does not have a separate power amp it is very unlikely to be more than a total of 80 Watts ( 4 outputs at 20 Watts to each speaker )
despite what may be printed on the box or leaflet.

Plus there are many different ways to measure power, RMS is the scientific way but gives the lowest figure so makers tend to use meaningless figures such as "Peak Power Output" or even "Power Peak Input".

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Re what wire to use.

Common sense plays a big part here.
If you feel the need to upgrade the wiring, then you might as well get some nice thick stuff as it is not much dearer than everage stuff.
Mains cable is fine, especially as it is useually double insulated so is less prone to chaffing through against rough metal edges ( though you should avoid this of course anyway, with rubber grommets etc ).

Plus you can twist the 2 or 3 wires in the mains cable together to double or triple the power handling.

Always use earth wires, from the radio (or amp), that are as short as possible and go to a nice bright good connection to a bare bit of metal bodywork. This will help eliminate unwanted noises. Don't forget this wire needs to be as thick as the power wire !!

If adding wires to the battery ALWAYS stick a suitable high quality "inline" fuse, right close to where the wire is connected to the + positive terminal on the battery.

All this is for wiring a "normal" stereo.
If you are wiring a huge "max power" type 100000 Watt system, then you have more boring stuff to learn ( I can go on if you want - or have I gone on long enough, probably)

Heh, I knew about Bling Watts which is why I was peeved that there wasn't a clear input Wattage in the bumf that came with the head unit.

I'll probably leave mine as it is then as it is for normal use only, mainly radio 4 and traffic reports, the big speakers only being a practical requirement due to diesel and road noise. It's wired to the constant power in the dash and eartheed to one of the many earth spades to be found next to the fuse box (doesn't everyone have these?).

My GF on that otherhand seems to be building a bling mini and wants ICE!! No dash, no previous install, battery in the back. She has her eye on amps and many many speakers so I may well take you up on your offer to bore for your country.

Perhaps you and Dave should get together and do an ICE bit for the Wiki?

Good point about the bulb BTW, never thought of that!!

When i fitted a sub under my seat , I wired that straight to the leisure battery using mains cable and an in line fuse supplied, the power lead ( connected to ariel) that activates the sub from the head unit is a long cable using mains brown wire.

Why are the 2 signal cables from the sub to the back of the head unit so fat? They take some disguising around the rubber floor.

banana wrote: Why are the 2 signal cables from the sub to the back of the head unit so fat? They take some disguising around the rubber floor.

2 schools of thought on this one.

( As you may know, there is no appreciable current at all flowing in the signal cables ).

1 = Some Hi-Fi purists can hear the difference between cheap thin cables and expensive, thick, fancy cables. Whilst this may be true on a £3000 home "real" Hi-Fi system, I am sure it does not apply to the average I.C.E. system!

2 = There is more outer earth braid shielding the actual inner signal cable, this might well reduce unwanted noises being picked up from the high voltage elements of the ignition system etc.

very interesting read GHOST yep i have wired my head unit straight of the battery as i run 2 amps+subs much better and run 1 amp of main battery and 1 amp of leisure battery this made a hell of a difference when i done it
as for home systems ghost i got a biggy cost me a fortune collected it up over 3 yrs and now dont use it, all seperates, 6 in all and 4 speakers shame really but no were for it to sit now the missus has had her way will have to catch up only down the road from you

the above has been added to the wiki

From ther wiki
if your not sure which tab is which is which touch a 9 volt battery to the wires and note the direction the speaker jumps, if it jumps out the wire you touched the positive side of the battery to is the positive terminal on the speaker. (only do this momentarily) needless to say make sure any wiring is secure and insulated. I understand that soldered conections with heat shrink are the best. You wouldn't be the first one to lose a van to dodgy wiring if it burns.