Ok so I installed my new Sony head unit but there was three extra wires on the loom that I didn't know where they went and now my fuel gauge and trip computer don't work my car is a 99 sports I did the lazy way and cut the loom off and rewired.

What color are the three wires?

Black, green, and grey I think. Not looking at them at the moment
There is also a smaller plug that came out of the standard hu that had one blue wire coming out of it.
When the head lights get turned on the green wire gets power

They are on the wires closest to the centre of the plug all the wiring diagrams I have looked at say do not use

Can you take a picture for us? Are the left over wires on the car end or coming from the HU?

A typical Magna HU connector will have:
12v constant
12v accessory
4 speakers (so 8 wires)
Illumination

A typical included-in-the-box connector with a headunit, depending on the brand,will have:

12v constant
12v accessory
ground (very important, don't forget this, step 1 if the damn thing doesn't work)
8 speaker wires (usually grey, white, purple and green, and the opposite polarity for each wire has a trace (line)
amp turn on (basically puts out 12v when the HU is on)
power antenna (12v when in radio mode - your car might not have a power antenna so tape this up
illumination

Also check all fuses, mainly the two in the engine bay fuse box. They're located in the yellow box.

Did you disconnect the battery? My bet is you didn't and you have blown the fuse.

Heres an idea, please provide us the model number, I can tell you exactly what the wires are, where they belong and what your problem is.

Plus that black wire, is the ground if its not hooked up the unit will not work. Green and Grey normally would be the speaker wires as most people keep the solid blue/blue with white strip for antenna, remote line there may be an orange one for illumination and depending on the model it may have a mute wire too but I doubt it.

The head unit works the ground wasn't the black wire but it was red the coming from the cars wiring couldn't find an accessories wire so I hooked it up to the cigarette lighter wire the constant was yellow and the head unit works
It's a th magna sports

The head unit is grounded via it's frame. There is no ground wire going to the head unit.

That smaller plug with the blue wire only goes to the phone connector. Does nothing.


This link has a PDF that has the pinouts of the plug you cut from the car. Wire colours should match.
http://www.aussiemagna.com/forums/showthread.php?t=52841

The head unit works the ground wasn't the black wire but it was red the coming from the cars wiring couldn't find an accessories wire so I hooked it up to the cigarette lighter wire the constant was yellow and the head unit works
It's a th magna sports

You didn't answer any of my questions so I cant help you.

The head unit works the ground wasn't the black wire but it was red the coming from the cars wiring couldn't find an accessories wire so I hooked it up to the cigarette lighter wire the constant was yellow and the head unit works
It's a th magna sports

Pretty sure ground in Magna's has never been red... how did you come to that assumption?


The head unit is grounded via it's frame. There is no ground wire going to the head unit.

That smaller plug with the blue wire only goes to the phone connector. Does nothing.


This link has a PDF that has the pinouts of the plug you cut from the car. Wire colours should match.
http://www.aussiemagna.com/forums/showthread.php?t=52841

All headunits I've dealt with have a dedicated black ground wire.

Pretty sure ground in Magna's has never been red... how did you come to that assumption?



All headunits I've dealt with have a dedicated black ground wire.

Sorry I ment to say the stock head unit in the magna has no ground wire.

Wire everything back to standard and get a plug and play harness from supercheap or autobarn...easiest and safest way...if all else fails anyway (and look for blown fuses) Actually...they should have a bare wired harness from your car to a Sony as well.