Weird constant 12v problem

[LK1]

Recently refitted my aftermarket HU and its not working when wired what is correct:

so i changed it in the end to this wihich works:

now the problem is my 12v constant feed isnt constant, sometimes i will go turn the stereo on and the preset staions are lost and some times they are not, and the anti-theft L.E.D. does work either when the ignition is off. Anyone an ideas as to whats the problem?

 

[NeX]

the red wire should be your ignition wire and the yellow should be your constant.

if the yellow wire is not wired in at all then every time you take the key out you will loose your pre sets etc.

the but if you don't have the red wired in then the HU won't switch on with the ignition.

if you have red going to yellow and yellow going to red then the stereo will be on all the time...

what you want is it wired like it is in the first diagram. if it doesn't work like that then tell us what it's doing when its wired like that and we can work out how it should be wired

 

[LK1]

yes i tried wiring it like in the 1st diagram and it will not turn on at all, it will do nothing at all!

 

[Alienfish360]

just find a permanent connection with a multimeter, couldn't find one on Paddy's at all, so I helped him wire a fused cable to the positive of his battery.

 

[LK1]

Thing is i know there is a constant 12v feed as it was working before i refitted it and i had the electronic tuner radio as standard before upgrading

 

[ollie240585]

If you can't find the live feed, wire it up as alienfish said to the car battery (just make sure it's fused) Fuse closest to the battery as poss!!

Be a piece of cake!!!!

 

[LK1]

I'd rather not do that as it working round the problem rather than solving it as I know one is there but either i'm wiring it wrong or the wire is tempermental

 

[Alienfish360]

cables don't ttend to be tempromental, get a multimeter, and test for a permanent 12v

 

[NeX]

check ALL the fuses, one time my interior light stopped working and it was on the same fuse as something completly different!!

right first of all:

take the HU out and do what the others said, test the yellow wire comming from the car side of the loom for power. the dodgyest way of doing this is touching it against something earthed (a bare metal part of the car) if it sparks you know its live and working. if it doesn't spark which it shouldn't from what you've discribed then check all the fuses including any that may be inline with that wire or on the back of the HU etc cos you'll be supriesed what fuses can blow
if all fuses are OK then the only thing you can to is trace the wire which is near enough impossible without taking all the dash out etc so not worth doing but you could check the haynes manual to see it there is anything else using that wire which could be causing a problem...

THEN your last resort is to run a new wire, making sure it is a decent guage and has a fuse as close to the battery as possible because it will be carring a direct route to the battery and your car will go up in smoke if it makes contact with the body of the car and there is no fuse!! believe me it happened to me on some dodgy fog lights that i wired up and i nearly died!!! so ALWAYS use a fuse... if possible one at each end

hope this helps mate, let us know how you get on

 

[Yom]

If it works on and off I'd be more tempted to suggest your wiring is dodgey.

Failing that you could have a crap new headunit. Or the new fuse which came on the headunit's loom is crap and breaking the connection randomly (connectors not solid, in otherwords, ####ty wiring).

Goodluck anyway

 

[LK1]

thanks for the responses, i've now found out that it is the wiring that is originally in the car (not HU or its wiring loom). Is there any fuses along the wire I should check, if so where? or do you think its something with the actual wire?

 

[Yom]

There could be a crushed wire in the loom. The 12v constant for the stereo is one of those 2 plugs attached to the positive lug on the battery loom afaik.

Check for any wiring issues there first. Failing that you really should isolate the constant 12v for the radio and just run a new wire. There could be a potentially dangerous situation otherwise - mainly if that 12v is grounding somewhere on the car. I've seen the results of this sort of thing - lets just say the car was "medium rare" afterwards.

 

[NeX]

thanks for the responses, i've now found out that it is the wiring that is originally in the car (not HU or its wiring loom). Is there any fuses along the wire I should check, if so where? or do you think its something with the actual wire?

check em all mate,

any fuses you can find, including ones in the engine bay. fuses, unless fitted after market, will be easily accessable so if you've checked all the fuses you can see then there souldn't be any others.....

 

[LK1]

Sorry been on holiday! Got it working though thanks to everyones advise!

 

[ollie240585]

Nice 1 mate!!!

Glad 2 hear our random rants help in the end