Locate The "power Supply Harness"

asilverblazer · January 31, 2009

OK, I need to locate this bundle of wires for my amp turn on. This harness contains six wires, 2 wires with red and white insulation, 2 black wires, 1 light green, and 1 light blue.

Here is a hint, under the instrument panel near the center of the vehicle.

asilverblazer · February 1, 2009

Nobody?

Its in the wiring diagram... Looks like might be referred to as the mobile radio power...

Bluedog · February 1, 2009

It's only there if the truck has an "upfitter" option (typically for police or EMS vehicles). Otherwise take the power off of the MBEC down by the emergency brake. That's where the harness originates.

ScottyBoy · February 1, 2009

You can't get an amp turn on wire at the fuse panel or ign harness?

ScottyBoy · February 2, 2009

Are you trying to find a retained accessory wire to power on your amp? If thats what you are doing, you can just make your own RAP wire. You can do this one of two ways with a few relays and diodes. Let me explain:

If you wish to keep the radio (or any other device that is powered by an accessory circuit) on until a door is opened, you can do so by creating a latch when the accessory is turned on with the relay shown below on the left, then breaking ground to the latch when a door is opened as shown with the relay below on the right. While this will keep the radio on, the entire accessory circuit will see 12V+ until a door is opened with the key in the off position

If you want to prevent 12V+ from feeding back into the accessory circuit or have more than one device on this circuit and do not want all of them to stay powered, you can isolate the device you want to stay powered by cutting the accessory wire going to it and adding two 1 amp diodes and an additional relay as shown below. The first diode near the top left of the diagram is to prevent 12V+ from going back into the accessory circuit. The second diode between terminals 87 and 86 prevents the radio from pulling current through the first diode. If the second diode is not in place, the first diode will become toast. The additional relay is needed to prevent the radio from turning off when the key is in the accessory position and a door is open.

I'd probably wire it up like the bottom setup.

Hope this helps you out a bit!!

asilverblazer · February 2, 2009

It's only there if the truck has an "upfitter" option (typically for police or EMS vehicles). Otherwise take the power off of the MBEC down by the emergency brake. That's where the harness originates.

Can you narrow it down to hhich plug, pin? Maybe I need to talk to a parts guy and buy this goofy harness. Plug and Play compliant.

asilverblazer · February 2, 2009

Are you trying to find a retained accessory wire to power on your amp? If thats what you are doing, you can just make your own RAP wire. You can do this one of two ways with a few relays and diodes. Let me explain:

If you wish to keep the radio (or any other device that is powered by an accessory circuit) on until a door is opened, you can do so by creating a latch when the accessory is turned on with the relay shown below on the left, then breaking ground to the latch when a door is opened as shown with the relay below on the right. While this will keep the radio on, the entire accessory circuit will see 12V+ until a door is opened with the key in the off position

If you want to prevent 12V+ from feeding back into the accessory circuit or have more than one device on this circuit and do not want all of them to stay powered, you can isolate the device you want to stay powered by cutting the accessory wire going to it and adding two 1 amp diodes and an additional relay as shown below. The first diode near the top left of the diagram is to prevent 12V+ from going back into the accessory circuit. The second diode between terminals 87 and 86 prevents the radio from pulling current through the first diode. If the second diode is not in place, the first diode will become toast. The additional relay is needed to prevent the radio from turning off when the key is in the accessory position and a door is open.

I'd probably wire it up like the bottom setup.

Hope this helps you out a bit!!

Sure I could do that, but finiding one of these other mystery wires would be my first choice. I am also looking into some wires labeled accesory voltage.

Thanks for all the replies.