Boost14

I’m trying to install an aftermarket double-din stereo head unit in my 1992 SC300, but I’m having a wiring problem.

It appears that a previous installer had followed the guide described by the Club Lexus forum member raine. “HOW-TO: SC300/SC400 Install Aftermarket Head Unit, OEM Speakers and Sub Working!”

I don’t get any sound through the stereo when wired into the teal green and blue wires in the trunk.

These are the wires that go to the front-right speaker, the passenger side. If I disconnect the gray and gray w/ black wires (right front + and -) at the stereo connector then I get sound.

I’m thinking this has something to do with the original factory phone transceiver that is no longer present. The phone system audio was passed to the front right speaker through the teal and blue wires.

At the stereo connector there is no continuity between the gray w/black wire (right front - ) and black ground wire. So it doesn’t appear to be shorted to ground.

With key off there is 15 volts present between yellow wire (battery) and gray w/black (right front - ).

With key on there is 15 volts present between red wire (accessory) and gray w/black (right front - ).

For the stereo to work there shouldn’t be voltage present on the speaker connection.

If anyone has any insight, I’d appreciate some direction.

Thanks, Joe

Boost14

After looking at my earlier post it might be confusing why I was getting 15 volts. I double checked the reading at the battery and my meter still said 15 volts, so I tried a different volt meter and this one measured the battery voltage at 12.1 volts. That makes much more sense.

I wondered if maybe the factory sub woofer amp on the rear package tray might be a cause of the issues I'm having. I removed the rear seats and package tray and I could see some wiring splices. As a test I disconnected the amp plug. This was after various other troubleshooting tests. Now the stereo head unit did not turn on at all. Reconnect amp but still no power to stereo. All fuses tested good. The problem seems to be the brown ground wire that is connected to the stereo connector's black ground wire.

I instead grounded to the chassis bolt under the center console and the stereo powers up and now I get sound out of my right front speaker. I really don't know what the original issue was or why it now works but it seems to be working. I need to clean up the wiring, put it all back together and figure out if the subwoofer works but for now at least I get stereo sound out of the head unit.

Thanks for all the help, support and suggestions. I couldn't have gotten it with out all of your assistance.

Joe