Ok, many thanks to those who offered suggestions on which wire to tap for the manual antenna switch I was wiring to my sc-815.

Here's what you need if you also want to install a switch so the antenna doesn't stick out like a sore thumb when you only listen to CDs.

1) Switch - cost between $25-50 depending on the dealership

(location# 1001 08034 part# 9447386) OEM on the S90/960

you should also buy the harness with the switch unless you can tap the wires yourself.

2) Remove the radio 1)by pushing in the slim tabs on the edges of the radio. 2) pull the levers when they have extended.

3) The trigger wire for the power antenna is the solid RED wire on the large-14wire-connecter on the back sc-815/816. Its location is the third wire from the left on the top row. Just cut that wire and connect it to the Volvo OEM Antenna Switch that fits nicely on your dash (in the vacant spot to the right of your steering column).

BTW, I didn't bother to hook up the illumination wires for now, if someone figures out which wires to tap into please post here.

Thanks!