Trying to upgrade my 92 740 Volvo wagon's radio.

Bought a JVC unit.

Trying to do this on the cheap, so I didn't buy any plugs (I know) and I'm in too far to go back now (I know, I know).

I've got everything working fine except:

I don't know how to wire the door and back speakers into the amplifier plug.

Also, the radio shuts off when I shut off my headlights, but I don't have any headlights unless I wire it up this way.

I have had a heck of a time finding wiring resources online.

Your help will be greatly appreciated.

 

It's not easy, but it can be done. The car has a separate amp. They don't make a simple adapter harness.

Here's what I got. Check out the pic, the center section is the US radio connections. These are based on my '98 740, so I think that the wires for the radios would be the same.

Here's a guide to the numbers:

8 Instrument lights (for dimming)
11 Fuse box
40 Trunk Light
137 Headlight relay
147 Aerial
143 Speaker
144 Speaker
145 Speaker
146 Speaker
148 Power Aerial
149 Radio
346 Roof light, trunk
490 Power Aerial Switch
901 Amp

"SB" means black (svart in Swedish I think). The rest of the colors should be easy.

It's my guess that you took power from the 137 connection, but you need to take it from fusebox (11). You can see a set of smaller numbers following the "11" number for the fuse box. On the amp it 11 the a small 26:2. 26 is the fuse number. So there are two connected to the radio. 11 14:2 on the left and 11 5:4. Different ones may have power always on or switched with the key. Pic the ones you need for proper function. You can also match the amperage load of the new radio to a suitable fuse in the box. These particular fuse numbers may be different in your car. I'm not sure if the switched the fuseboxes up on later model 740s.

Good luck!

 

OK, that helps.

I think I can figure out all of the speaker wiring once I access the wires at the amp.

My only two issues are:

1. Radio only working with headlights on (2 yellow/white wires hooked up) or no headlights (2 yellow/white wires unhooked).

2. No illumination on instrument panel.

Assuming these issues are related as they are both power issues.

So hopefully tonight, if not, tomorrow night, I'll address the 4 door speakers and get them working. Then turn my focus to the headlights and instrument panel.

Then,

 

Got all my speakers hooked up!

AND got my instrument panel to light up.

Now the only issue I have is the radio only works with the headlights on.

Is Titan Joe's comment the fix to this?