Does anyone have the wiring diagram for a 240? After I installed a tachometer in my 91 240 the radio has stopped working (no Power). I think something may have gotten disconnected and am not sure what. There are two wires feeding power to the unit one yellow and one red (test light). Then there are the 8 sets of speaker wires that run to the harness(4 front + 4 rear). Then there are two blue wires that from the hareness that are not connected to anything as well as a thicker black wire that as well isn't connected to anything that (I'd assume the black wire would be the ground). I had a problem early when the antenna wasn't retracted no power would feed the headunit, I checked and double checked the antenna but no luck, I even used another antenna. No I am stumped. The head unit is a Sony cd, don't know the model off hand.
Thanks for any help.

i have a 1978 volvo 240, and the Memory (12.6 volt constant) was blue and the Ignition (12.6 volt switched) was black. for some reason volvo had the magnificent idea to make both the power wire and the ground wire black. the difference is that the fat black wire is your ground, the thin one is your ignition. and if you're not grounding it, you should start with that.

this is a color code diagram i found online for volvo cars. i use the site to get the color codes for when i install things in my friends cars (nissans, hondas) and its generally correct. it doesn't match my car, but mine is also 24 years old. perhaps it matches yours.

Memory (+12 Constant) Green
Ignition (+12 Switched) Black
Ground (-) Fat Black
Illumination - Yellow (not on plug)
Power Antenna - Red

(http://robco.netfirms.com/wiring/volvo.htm)

if you are thinking the red and yellow are the power wires, this would explain your problem.


also, on your wire harness coming from your Sony, those two blue wires are for your power amp, should you choose to use one. i used to have a 1999 Sony cassette deck in the volvo, and the solid blue wire was the +12 switched, and the blue with a white line on it was +12 constant. i may have mixed the two up, but thats what they are used for. i didnt use the constant wire however because it didnt supply enough power but i did use the switched wire as my remote wire for the amp.

hope this helps. feel free to email me if you have any questions, or if i said something that seems unclear. -- phrewt@worldnet.att.net

Contact www.crutchfield.com. They will fax or email you the wiring diagram -especially if it's a Sony. Send a message to thier technical support center. They will usually reply to your emails even if you didn't buy anything from them.

I actually just bought some stuff from them and they are always a delight. Thanks I am not sure why I didn't think of them.

You might be better off running at least one new wire anyway. A few months ago I ran a heavy wire directly from the terminals near the battery to the yellow wire, and it improved the sound and the volume I was able to get out of my Alpine head unit. The Volvo wires are all on the thin side.

The red wire can be hooked to a wire that gets turned on with the key. And you need a good ground.

Consider running heavier speaker wires as well if you have good speakers, which means that if you put aftermarket stereo in you can just bypass most of the stock harness. Even cheap 12/2 or 14/2 will probably sound better than the stock wires.

While I was doing this I also added a switch to the center console that lets me play the stereo with the key off, good for when she's shopping for clothes. I ran an aways-hot wire from the fusebox to the switch, then ran a wire from the switch to the red wire. I put diodes in both sides to prevent activating something else, which might drain the battery faster. And I used a lighted switch (junkyard, coupla $$) to remind me to turn it off.

Any ideas why my head unit won't power up all of a sudden? Do you think that it needs to be grounded and that I seperated the ground some how? Is there a way to power the unit directly from the battery to test that the head unit is functioning. Finally, is the yellow wire supposed to be supplying 12 volts, what about the red wire?

Was I correct red and yellow wire are power. Then there are 8 wires for the speakers then one black wire for ground. Did I miss anything.

Oh yeah, the fuse in the back of the head unit is 10 should I put in a 12?

i have a 1978 volvo 240, and the Memory (12.6 volt constant) was blue and the Ignition (12.6 volt switched) was black. for some reason volvo had the magnificent idea to make both the power wire and the ground wire black. the difference is that the fat black wire is your ground, the thin one is your ignition. and if you're not grounding it, you should start with that.

this is a color code diagram i found online for volvo cars. i use the site to get the color codes for when i install things in my friends cars (nissans, hondas) and its generally correct. it doesn't match my car, but mine is also 24 years old. perhaps it matches yours.

Memory (+12 Constant) Green
Ignition (+12 Switched) Black
Ground (-) Fat Black
Illumination - Yellow (not on plug)
Power Antenna - Red

(http://robco.netfirms.com/wiring/volvo.htm)

if you are thinking the red and yellow are the power wires, this would explain your problem.


also, on your wire harness coming from your Sony, those two blue wires are for your power amp, should you choose to use one. i used to have a 1999 Sony cassette deck in the volvo, and the solid blue wire was the +12 switched, and the blue with a white line on it was +12 constant. i may have mixed the two up, but thats what they are used for. i didnt use the constant wire however because it didnt supply enough power but i did use the switched wire as my remote wire for the amp.

hope this helps. feel free to email me if you have any questions, or if i said something that seems unclear. -- phrewt@worldnet.att.net

On many units the yellow is the power wire that needs constant juice (otherwise your settings will be lost) and the red is the "trigger wire", which needs to be hooked up to a keyed wire.

So first check that both of those have juice, yellow always, red with key on. Make sure that you have a ground. Use a test light close to the unit so you can see whether the power is getting there. It could also be that the plug in the back is not in firmly. Or that one of the wires has a break, since they need to be stuffed in there.

Replacing a fuse with a higher rated one will almost surely cause you problems, and may destroy your unit.

If a fuse blew it could mean that one of the speaker wires has worn insulation and is grounding somewhere.

Again, the best idea is to install your own new wires, which assures that you won't have problems in the future. That way you KNOW.

It takes a lot less time to install new wire than to troubleshoot the old ones. Plus, you get better sound. But if you enjoy fault-tracing, have at it.

Both the red wire and the Yellow wire have in-line fuses located somewhere around the steering column. You'll need to replace these with a larger fuse, as most aftermarket stereos are much more powerful than the original.