Mach 460 is killing my Battery! Dies every few days, Aftermarket Sub woofer as well!

01Stang65

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Jan 19, 2017
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So I have been chasing a battery issue over the past couple years of ownership of my 01 GT. Every few days the battery completely dies if not driven. This draw already ate 2 batteries. Luckily under warranty. Doing some tests the other day, I disconnected the negative on battery and used a multimeter between the post and negative wire. The reading showed 11.09 amps. That doesn't seem accurate does it?

For the longest time I didn't have a direction but now I am lead to believe the issue is the 460 system, seems pretty common on these cars. A couple details though;
-Previous owner had a 10 inch sub installed in the trunk (never questioned it)
-Sometimes when the electronics would glitch, the sub wouldn't turn on, and I noticed controlling the bass on radio wouldn't do anything (telling me factory subs were not operating)
-That leads me to my question: Do the 460 amps just power the subs on our cars?
-When I turn the car on, the radio turns on, and then a second later the subs start working.
-I know one red cable runs from the back of the radio to the sub, I know one green ground runs from the trunk body to the sub, and then another green wire from somewhere else to the sub. Two thick brown speaker wires go from the amps to the subs.

Just trying to figure out where I should go from here. I have no problem just going back to stock setup, bass doesn't sound that good anyways.
 
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Mustang5L5

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Best way to find the draw is to pull fuses and see if that 11A current draw goes away.

Pull the Mach 460 fuse and measure current draw. Disconnect the aftermarket amp, and see if the draw goes away.
 

01Stang65

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Best way to find the draw is to pull fuses and see if that 11A current draw goes away.

Pull the Mach 460 fuse and measure current draw. Disconnect the aftermarket amp, and see if the draw goes away.
I must be doing something wrong... The longer I have the multimeter between the negative post and loom, the more that 11A "draw" goes up... even after letting the car sit for a bit off with doors latched and all, I can't get the draw to go down. I never heard of a 12 amp draw which is what the multi was reading this morning. Pulled the maxi 6 under hood and it was the only one to decrease the number. Pulled radio fuse under dash and no effect
 

Mustang5L5

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You're meter has a setting for DC amps right? Most I've seen are limited to only 10amps of current draw on DC.

11amps is a lot. That's like leaving the headlights on. I'm sure it could happen, but that's a significant drain akin to a dead short to chassis ground.
 

01Stang65

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You're meter has a setting for DC amps right? Most I've seen are limited to only 10amps of current draw on DC.

11amps is a lot. That's like leaving the headlights on. I'm sure it could happen, but that's a significant drain akin to a dead short to chassis ground.
DC and then I set it on the "20" setting.
 

Mustang5L5

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DC and then I set it on the "20" setting.

11A is significant then. That's why I was questioning how the meter was being used. I just wanted to make sure it wasn't accidentially set on DC volts, and you were reading 11 volts, which does make sense for a battery that's being drained. It would also make sense as to why the number increased over time.

Hook the meter up and pull fuses. Pull the radio circuit fuse, and also disconnect the aftermarket amps main power wire and see if this number drops. You need to isolate where the draw is coming from
 

01Stang65

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11A is significant then. That's why I was questioning how the meter was being used. I just wanted to make sure it wasn't accidentially set on DC volts, and you were reading 11 volts, which does make sense for a battery that's being drained. It would also make sense as to why the number increased over time.

Hook the meter up and pull fuses. Pull the radio circuit fuse, and also disconnect the aftermarket amps main power wire and see if this number drops. You need to isolate where the draw is coming from
You are correct, I was on DC volts... Switched it to DC amps and shows "0". While messing with all this I took the aftermarket sub out of the trunk, left the wires... Just an FYI there is no aftermarket amp, just an aftermarket sub
 

Mustang5L5

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Feb 18, 2001
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Ok, you should measure some draw. Flip the hazards on and see if that gets you a reading

You'll need to disconnect one terminal on the battery. Doesn't matter whichone. The multimeter sometimes requires a lead to put into a different plug to measure amps than volts. So make sure the black and red leads are in the proper spots for dc amps. Use some tape, and tape a lead to the post on the battery, and the other lead to the terminal that previously hooked to it. You should measure under 0.1amps of current draw. turn on the hazards (because I think they are under 10a of draw), you should see draw when the lights blink. That confirms you have it hooked up right.

Now, what do you get for current draw. If the battery is draining every 2 days, I would expect to see 1A or more of draw.
 

01Stang65

Member
Jan 19, 2017
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Ok, you should measure some draw. Flip the hazards on and see if that gets you a reading

You'll need to disconnect one terminal on the battery. Doesn't matter whichone. The multimeter sometimes requires a lead to put into a different plug to measure amps than volts. So make sure the black and red leads are in the proper spots for dc amps. Use some tape, and tape a lead to the post on the battery, and the other lead to the terminal that previously hooked to it. You should measure under 0.1amps of current draw. turn on the hazards (because I think they are under 10a of draw), you should see draw when the lights blink. That confirms you have it hooked up right.

Now, what do you get for current draw. If the battery is draining every 2 days, I would expect to see 1A or more of draw.
Aha yes! 10 amps when flashing. 1.6 ish amps draw.
 
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Mustang5L5

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Still a tad high. I believe you want about 0.03 amps when in standby mode. A 1/4 of an amp would definitely drain a battery in short time.

Start pulling fuses.
 
Dec 30, 2018
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So it sounds like this aftermarket kit was a home set up and maybe wired wrong which is unfortunately having you go through all this trouble. Your best/easiest bet is to start with the fuses like he said