Alpine 7840 has power but no sound. all speakers are connected corectly,except for a pink and black one. i have no place for it. what do i do?

If you contact Alpine they will be able to tell you if there is an adapter that will plug right into your existing OEM harness. If not then, you'll have to figure out Which wires are which on your OEM harness, here is the Alpine wire code:
Alpine wiring help

HU harness color code pretty much universal.
red=ignition
yellow=battery +
black=ground
blue/white=remote turn on
blue=power antenna
pink/black=audio interupt in (not sure if you have one)
speaker wires
gray=right front
violet=right rear
green=left rear
white=right rear
speaker wire with black stripes is negative.

Confirm this wiring for 2000 Nissan Altima Car Stereo Radio Wiring Diagram

Radio Constant 12V+ Wire: Pink
Radio Switched 12V+ Wire: Blue
Radio Ground Wire: Chassis
Radio Illumination Wire: Red/Green
Radio Dimmer Wire: Red/Yellow
Radio Power Antenna Trigger Wire: Green/White
Radio Amplifier Turn On Trigger Wire: N/A
Front Speakers Size: 4′ x 6′ Speakers
Front Speakers Location: Doors
Left Front Speaker Wire (+): Brown
Left Front Speaker Wire (-): Black/Red
Right Front Speaker Wire (+): Light Green
Right Front Speaker Wire (-): Black/Yellow
Rear Speakers Size: 6 1/2′ Speakers
Rear Speakers Location: Rear Deck
Left Rear Speaker Wire (+): Orange
Left Rear Speaker Wire (-): Black/Pink
Right Rear Speaker Wire (+): Blue
Right Rear Speaker Wire (-): Black/White

Hope helps.

Please let me know if you have any questions, and thanks for using FixYa.

2004 Toyota RAV4 Car Stereo Radio Wiring Diagram Alpine wire color
Radio Constant 12V+ Wire: Blue/Yellow yellow
Radio Ignition Switched 12V+ Wire: Gray red
Radio Ground Wire: Brown black
Radio Illumination Dimmer Wire: Green none
Radio Antenna Trigger Wire: N/A blue
Radio Amplifier Trigger Wire: N/A blue/white
Front Speakers Size: N/A
Front Speakers Location: N/A
Left Front Speaker Wire (+): Pink white
Left Front Speaker Wire (-): Purple white/black
Right Front Speaker Wire (+): Light Green gray
Right Front Speaker Wire (-): Blue gray/black
Rear Speakers Size: N/A
Rear Speakers Location: N/A
Left Rear Speaker Wire (+): Black green
Left Rear Speaker Wire (-): Yellow green/black
Right Rear Speaker Wire (+): Red violet
Right Rear Speaker Wire (-): White violet/black

This might help

http://content.etilize.com/User-Manual/1010312155.pdf

If the alpine 8020 is a deck(head unit) the wire diagram is as followed:

Red: Accessory
Yellow: Constant Power
Black: Ground
Orange to orange/white is a illumination or dimmer wire.
White: front left speakers
Grey: front left (white black and so on usually the negative on the speaker connections)
Purple rear left (purple black = neg)
Green: Rear Right
And if a video deck(light green is park brake)
(which is usually just a ground) so legally it needs to be on your park brake but can be grounded to make it work.

Speakers? (Terminals larger one is positive, smaller one is negative) Place capacitors on if needed to filter out and clear up bass

Hope this helps couldn't look uo what a alpine 8020 was..

Look on page 27 of this owners manual.
http://vault.alpine-usa.com/products/documents/OM_CDA-7840.PDF

PLEASE CHECK U ARE CONNECTING TO A PROPPER SOUND CARD IN A PROPER PLACE
PLEASE CHECK THE VOLUME LABLE IS HIGH OR MED .AND ALSO CHECK THE NOB IN BACK OF YOUR WOOFER THE BIG BLACK BOX IS APPRIOPRIATE VOLUME ATLIST MEDIUM AND SEEE IF U HAVE CONNET TO THE CORECT COLOUR CABLES IN CORRECT PLACE IT SHOULD WORK

Hi,

Depending on the vehicles wiring itself, Alpine uses the below color coding for its wiring:
yellow – constant +12v such as the positive battery terminal
red – switched 12v such as the accessory terminal of the IGN switch
black – ground which could be the chassis/body ground of the vehicle or the negative terminal of the battery
blue/white - remote trigger for add-ons such as a power amplifier
blue – will activate a power antenna (if present)
white and white/black - front left speaker + & -
grey and grey/black - front right speaker + & -
green and green/black - rear left speaker + & -
purple and purple/black - rear right speaker + & -
orange/white - reverse wire
white/pink - monitor control lead
pink/black - audio interrupt from mobile/cell phones
yellow/blue - parking brake
yellow/black - foot brake

To bypass, the yellow/blue must be triggered negative/grounded. Alternately, it may be easier to use an adapter such as a Peripheral PTR7 (http://peripheralelectronics.com/). In some regions, it is not allowed to operate this unit while vehicle is in motion.

Hope this be of help. Pls post back how things turned up or should you need additional information.

Good luck, kind regards and drive safe.

I have the exact same problem and it has been driving me nuts for several years now.  I have tried everything with no luck.  I finally resorted to buying a used faceplate on eBay (and they had several available so I suspect this is a common problem).  I will let you know how it turns out.

Some 4-Runners have a factory system that uses a separate amplifier to power the rear speakers. In this case you need to activate the amplifier using the blue/white remote output from your Alpine deck. It sounds like the wire that activates the amplifier is currently attached to the deck's blue "power antenna" output, so that the amplifier is only on when the tuner is selected. Disconnect whatever is attached to the blue wire behind the deck, and attach it to the blue/white wire instead. That should solve the problem.