F***ing radio in a 91' 740

[73 Cuda]

Hey,
I have a buddy that has a 91 740 and is trying to put a deck into it. There is no harness to directly hook from the deck to the volvo harness so he went ahead and cut the wires. Now his headlights don't work (high beam do as do indicators etc etc.) This is where I come in, he now has brought this car and being the magic man that I am, I am supposed to fix it. If anyone has done this and has any insite on what he has done, I checked most fuses and the harness just doesn't make sence to me at all. There is a wire going in to an amp and then the main harness. If anyone has a clue email me at.
[email protected]
thanks alot

Dean

[guest from nj]

my son put a new head in his car and now has no lights

there were two yellow wires on the original Volvo plug that were cut thinking they were speaker wires. after realizing that they were not, they were put together? and everything seemed ok. the electrical tape came off and one of the wires shorted on the radio box. no low beam headlights since then and no flip to high beams.

high beams work if the tiller is held into flash position
i do not hear a relay click in the panel behind the fuses.

so the question is whether there is no power to the light switch or relay or whether the short blew something.
any possible help posted here would be appreciated.

[guest from nj]

i found out what the problem was
on the factory harness to the factory radio plug there are two yellow wires [may have a trace?]
they are together on one connector and when they were cut off they separated
the light circuit goes through that connection so even if you do not use them, they need to stay together.
stupid design but hey, my sons car is now fixed.
[except that he burned the yellow wire that is the hot from the light switch so this weekend i need to run another]
guess it is for radio illumination.
too many hackers in the car wiring earlier