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Alan_Hepburn · 08-22-2013, 09:09 PM

My son is attempting to install a CD player/radio in his dash and has encountered a weird issue: the wiring harness that came with the unit (a Sony CDX-GT660UP) has three hot leads - power, display, and one other (I forget the name). He connected all three to a line that is hot all the time so he can have music without needing the key on. I already suggested that he change the display wire to a switched source to save the battery when he turns the radio off. He also connected the ground wire to a good ground under the dash. Checking with a voltmeter shows all three power pins in the socket have +12V as expected. But, when he plugs the connector into the back of the radio it applies +12V to the ground line!

I tried to do some troubleshooting for him so I disconnected the ground from the dash and when the connector is disconnected there is 0V on the ground line, but as soon as the connector is connected the ground wire gets +12V on it. I have no idea why that would be - it sounds like there is something wrong inside the radio, but he claims it worked when he first hooked it up. Anybody have any idea what might be wrong?

I tried looking up the model with google and that gave me pdf files of the installation guide and user manual that came in the box with the radio.

JohnInAz · 08-22-2013, 10:26 PM

How are you determining that you have 12v on the ground? Wouldn't that result in a dead short? Are you blowing fuses or burning wires? What is the radio doing?

Alan_Hepburn · 08-22-2013, 10:51 PM

Quote:

Originally Posted by JohnInAz

How are you determining that you have 12v on the ground? Wouldn't that result in a dead short? Are you blowing fuses or burning wires? What is the radio doing?

I disconnected the ground wire from the metal frame under the dash, then connected a voltmeter from the ground wire to the frame. With the connector disconnected the meter reads 0V; with the connector connected the meter reads +12V. If we take that ground wire and touch it to any piece of metal under the dash we get sparks if the connector is connected.

We don't have any blown fuses, or burnt wires - I suspect it's a low current involved because the sparks aren't real strong, but it is definitely a short of some kind.

The radio is sitting on the floor, silent and dark - probably laughing maniacally at us

cb1000rider · 08-22-2013, 11:13 PM

What you see is normal. It's not considered a "short" because it's essentially the radio load that you're seeing.

I know it sounds odd because it's a ground wire, but if you were to cut the ground wire in your car and insert a volt meter, you'd see the same thing - with a lot more current... :-)

JohnInAz · 08-23-2013, 12:02 AM

It would be normal to see a spark when you connect it since the radio has a constant draw, which is what you are seeing on your meter (a completed circuit). I would verify that you have all the hot wires connected properly, or better yet, just connect the clock to power and see if you get the clock features, etc. working. You stated that the radio worked when it was first hooked up. What changed?

Tha_Rooster · 08-23-2013, 12:47 PM

The third is probably for a dimmer switch.

greezykid · 08-23-2013, 12:53 PM

I just installed a new sony dash radio today in about 1/2 hour,all the wires are color coded the same.Just match new wire colors to old wire colors and you should have it right.