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For Christmas, St. Nick left my wife a new CD/Stereo/iPod player for the '91 Spider. While installing it yesterday, I ran into some problems which prompted me to search this board. I've looked back through all the notes about installing radios in S4 Spiders, but the subject is not covered in much detail.

I noticed some issues on connecting newer radios to the wiring harness. I'm not sure what was causing problems since a simple solution is to splice male spade connectors on each of the wires of the harness that comes with the new radio. These will insert firmly into the female terminals in the two stock connectors behind the dash.

There are six female terminals in the power connector and eight in the speaker connector. The Service Manual shows the correct configuration for the power connector.

1: Ground, black
2: Open
3: 12v to antenna, blue/green
4: 12v to radio illumination, white/black
5: 12v constant to radio, red
6: 12v switched to radio, blue/red

At the radio relay, post 30 feeds switched power to the radio wiring harness. Post 85 runs to ground. Post 86 is powered from the ignition switch. Post 87 is 12v constant. It should be possible to use any fused ISO 4 or 5 pin mini relay that is closed when active in this circuit. [My CarDisc incorrectly shows the radio relay wiring as 30 to ground and 85 to the harness]

There is supposed to be a blue/red 16g wire that feeds the relay from the ignition switch. I was unable to locate any such wire and the relay is not being activated to provide switched potential at pin 6 of the radio connector. Am I missing a wire or has one of the PO's installed a different ignition switch?

When we got the car, it had a sophisticated sound system. As is common enough in car audio systems, the CD player had become unusable. Repair is not economical, so I opted for replacement.

Noting the wiring situation mentioned above, the receiver had been wired only to 12v constant. The car has shown a tendency to drain the battery when it's sitting idle for more than one week, so I wanted to have switched power to run the receiver to avoid any needless drain on the battery.

In the absence of a feed from the ignition switch to the relay, I tapped into the 10g brown wire that powers fuses 6-8 from the ignition switch and jumped to the blue/red wire from slot 30 in the radio relay position in the fuse panel. This provides switched power to post 6 in the radio power connector. Constant 12v to preserve the clock and other stored information on the system comes from fuse 5 to post 5 in the power connector.

The speaker wiring connector in the service manual is not the same as I found in my car. Below I’ve shown the latter configuration:

Posts 1/2: Left rear, gray/black and yellow/black
Posts 3/4: Right rear, yellow/green and blue/black
Posts 5/6: Left front, blue and blue/black
Posts 7/8: Right front, gray and gray/black

The speaker wires in the radio harness were all labeled with respect to the speakers they feed and polarity. I think this is standard on all modern receivers. This makes it installation a simple matter of connecting to the corresponding wires in the stock connector through the use of male spade terminals.

It’s important to assure correct polarity throughout the system, and you’ll have to check the current installation to determine it since the service manual doesn’t provide guidance. Frankly, I would have expected Alfa to use one solid color wire and one stripped wire in each set, but they chose this for only the front speakers with different color combinations for the rears.

The audio system is working as it should and my wife is happy to have a CD again.


'86 Spider Veloce
'87 Milano Platinum
'88 Milano Gold
'91 Spider
'95 164LS
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