Trying to connect a Pioneer head unit in my '99 S70. The wires in the vehicle harness clips do not match the wires on the adapter harness/Pioneer wiring. The colors are different and there are more of them on the vehicle side. I have found a diagram below of the clips that seems logical:

https://www.tehnomagazin.com/Auto-ra...-Connector.htm

These are the wires that are connected to the stock radio:


More wires present there than the diagram above outlines. Notably, two black wires (ground?). If anyone has any insight/advice as to which wires are which it would be much appreciated.

 

You have all the answers on the Volvo side in your diagram (example it shows pin 1 and 7 as ground thus the two black wires - this is done to allow the chassis ground to extend to the speakers/amps etc.) You may be able to find an adaptor kit at Crutchfields.com or on eBay if you are unsure about how to splice up from the Pioneer unit's harness. Just break down the wiring into the various components ie system power and system ground, power/ground out to the antenna (tells it to go up/down) and any aux amps (tells it to turn on/off), signal and return (ie ground) to each of the 4 speakers etc or signal/return to an aux amp etc.

 

Much appreciated. I came to the conclusion that I was looking at the wrong diagram on that page. Duh. I take it this is the (correct) one you are referencing:


Assuming that is the one, the adapter harness I bought looks like it is pinned correctly aside from not having all of the wires that are present on the vehicle side. When I first connected the Pioneer unit, there was no power and it blew the radio fuse. Do I need to tie in the extra ground, 12V wires? FYI this is the adapter I am using:


Thanks again!

 

tying in the extra ground helps prevent any "ground loops" which can cause speaker noise or radio interference. The better the ground the cleaner the sound :-)

 

Jumping in here, not because I'm doing an aftermarket install but because I'm chasing down bad speaker noise on the left-hand front and back speakers of my brother's S70 (the HU is an SC816). Was very gratified to read mt6127's proverb "better ground makes better sound" because I had a feeling that a bad ground was making for sh*t sound on the left-hand side... now am I right that 1 and 7 are the grounds for left and right channels? If so which is which and where do they go to the chassis so I can look into cleaning one of them up? All wiring on the inside of the car looks clean (been testing continuity from speakers to HU connectors) and I've determined that the problem is not the speakers themselves (actually swapped left and right front door bass speakers, whichever speaker is on the left sounds like garbage (same with the front dashboard tweeters))...

Looking forward to the education as always