I just installed in my 1992 Volvo 960 Wagon a Blaupunkt Casablanca CD51 which my mom bought for $129 as a X-mas present from Crutchfield's. Their tech support is great. The original Volvo radios had dash speaker wires direct from the radio and the four door speaker wires from the Volvo Amp output. The Volvo amp is not compatible with aftermarket radios and must be bypassed. The wire harness Crutchfield has for the 940 works only on the 1992 960 Wagon. Later years of 960s use a different harness that they stock as well.

Since the after market units only have wires for 4 speakers I have seen earlier posts by Volvo owners who have left their dash speakers disconnected. The tech support told me I can still utilize the dash speakers by wiring them in series with the front door speakers which will increase impedence from 4 to 8 ohms. I tried it and all six speakers work well. With Polk Db650s in front doors and Db525 in rear doors I really hear the inadequacies of the factory paper cone dash speakers at higher volumes. I don't know if I can wait until my birthday in August to replace them.

My new radio has an automatic volume compensator which increases volume as the speed increases. A single wire for this function is supposed to connect to the speed sensor wire going to the speedometer. The problem I face is that Volvo has two speed sensor wires(+ and -) going to its speedometer. Has anyone addressed this issue before?