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General => Car audio => Topic started by: Pennith on 05 November 2007, 10:06

Title: Not enough Power going into Head Unit?
Post by: Pennith on 05 November 2007, 10:06

Hello,

Got a Golf Mk4 GTI '98, bought it in April, last week head unit stopped working, so i thought it might be knackered, bought a new one and when i plug it in the eject mechanism whirs for a bit and thats it. Took it back to the shop(Halfords), tried 3 more HU's and the same thing happened - Tested it on their "test" board and it didnt work, but he was told after that the test board didnt work. lol. 

I checked the fuses and I have used a volt meter and the live wires are showing about 12v.

Before I take it to a car audio specialist, I was wondering if i could get any pointers/suggestions - go easy on me though :-)

Cheers

Title: Re: Not enough Power going into Head Unit?
Post by: Heyho on 05 November 2007, 20:24

You say that you have good feeds, but is your earth OK?

It must be the time of year or something - a lot of dead headunits about!

Title: Re: Not enough Power going into Head Unit?
Post by: Pennith on 06 November 2007, 08:44

It is earthing ok - is there anything else i can try? Thanks

Title: Re: Not enough Power going into Head Unit?
Post by: Heyho on 06 November 2007, 20:21

If you've got your 12v permanent and switched feeds, plus a good earth, your initial diagnosis may be correct... :cry:

Title: Re: Not enough Power going into Head Unit?
Post by: Pennith on 08 November 2007, 08:40

ok cheers :-)

Title: Re: Not enough Power going into Head Unit?
Post by: peaky83 on 08 November 2007, 20:05

I've experienced this before... Try connecting the head unit and measure the voltage with a multimeter...

When i had it the power connections showed +12v DC (approx 12.32v engine off and 12.72v engine on), however when i connected the head unit the readings dropped to 2.7 v engine off and 3.02 engine on....

So i came to the conclusion the original power wiring was faulty somewhere.

Simplest fix would be to run a new Live power wire (12amp cable and install a 10amp fues along it) then re-try the head unit and if it doesn't work still try running a new earth either from somewhere on the Chassis/car body or direct from the battery...

I'd run from the battery.

Hope this helps

Dan

Title: Re: Not enough Power going into Head Unit?
Post by: Heyho on 08 November 2007, 20:45

Dan has a point - hence my recommendation in one of the many "dead head unit" threads to use a testlight or just bulb when testing power supplies, not a multimeter.

It's not common, but I've spent ages diagnosing electrical faults in the past, only to find that a fuse was actually cracked - it was showing 12v without load, but it was not able to pass any current.  Even corrosion on plugs/fuse contacts can cause this.