Battery Drain Amp?

Let me help you with a thought experiment.

There's a control wire (normally blue) between the radio and amp. The purpose is to allow the radio to power up the amps. This is because the amps are on an "always on" circuit. Let's say the problem is in the radio and not in the right amp. If true wouldn't this affect BOTH amps? It seems to me since it affects only one amp the problem is most likely in the amp.

The final part of this thought experiment comes from the fact the draw problems go away when the right amp is disconnected.

Want more proof, see Occam's razor.

https://simple.wikipedia.org/wiki/Occam's_razor

Aftermarket radios all put power on the remote wire to turn the amp on. BUT, OEM's do weird stuff. It may be possible to tell with a wiring diagram, if they are actually grounding that wire at the radio to turn on a power relay in the amp. If that's the case you may have a grounded out wire somewhere between the amp and radio. Or test it with a volt meter and see if there is still power on that wire when the car is off. If there's power on that one but not the other one, then it might be a bad radio.

Where is the amp getting its power when the key is off? Sounds like the head unit, but I am still learning too!

Neuron said:

Where is the amp getting its power when the key is off? Sounds like the head unit, but I am still learning too!

Click to expand...

As the amount of electrically operated devices in the car increases this has the effect of increasing the amount of current needed. In the old school way of doing things this current would be run through the ignition switch. This causes the ignition switch to need to switch ever larger amounts of current. The switching of high currents wears out the contacts.

The other thing that has happened is people want more "features" in their cars. One feature is the ability to listen to the radio with the motor off. Think about HOW it would be possible for the radio to stay on until the driver's door has been opened if the radio's power ran through the ignition switch. For these reasons more and more circuits are run through "always on" power. Through a series of pilot duty low current control signals, the devices are powered on or off as needed. This saves wear and tear on the ignition switch as well as to give greater control to the device in question.

The radio head unit gets two power feeds. One is "always on". The other is powered when the key is on or is routed through the GEM. The head unit then signals the amps to turn on or off via the blue control wire. Because the amps need soooooooo much more power than the head unit, they are on individual always on circuits and are supposed to power on only when they are told to via the blue head unit control wire.

Great explanation, thank you!

I am new so I don't know if anyone has suggested checking your alternator! I have a 2004 mustang that drove me crazy. I checked all the circuits,and all checked out good. But to make a long story short a friend of mine who rebuilds starters and alternators etc checked my alternator and found it had a bad diode allowing my battery to discharge. I hope that helps someone.