Battery still losing power/current

T-Man1971 · Sep 9, 2016

Hi! I have a problem with 66 Coronet. My Coronet lose current somewhere, but i don't know where. I have done new wiring to engine bay and rear headlights. And week ago, i bought new wiring harness under dash from Classic Industries. Only thing i haven't rewire is front headlight and interior light. Still car is losing power. Somewhere is earth leakege. Can anyone help me? I have owned car five year, five battery. Please, don't tell me to use the main power switch. It doesn't solve the problem. Sorry if there is some mispelling.

Mike67 · Sep 9, 2016

If you want to narrow it down to which circuit it is you can either pull the fuse and with an ammeter put it in series and see where you have current flowing with everything off.
The other way is to pull the fuse and lift the battery cable until you find the one that keeps it from arcing when you reattach it unless it is up stream from your fuseblock...

PurpleBeeper · Sep 9, 2016

Mike67 said:
If you want to narrow it down to which circuit it is you can either pull the fuse and with an ammeter put it in series and see where you have current flowing with everything off.
The other way is to pull the fuse and lift the battery cable until you find the one that keeps it from arcing when you reattach it unless it is up stream from your fuseblock...

This is basically how I track down my wiring problems. You obviously have a short to ground somewhere. I believe you need a good/professional multi-meter to run the current through it. It's just a matter of elimination & a wiring diagram is REQUIRED. You just start disconnecting circuits until your amp/voltage drop goes to zero.

Sorry to get basic.... for example. Disconnect the positive battery post, connect a good meter with one lead to the disconnected + cable & the other meter lead to the + of the battery, you should be showing something like 1-volt (or whatever) which is the current being lost to your electrical short. Then, one at a time, you disconnect circuits. For example, pull fuse #1 and see if the 1-volt on your meter is still there. If yes, put fuse #1 back in & pull out fuse #2 and so on. If none of the fuses being pulled make your meter drop to "0-volts", then start disconnecting wires at the bulkhead disconnect....again, one at a time. Once you find a circuit (either the fuse or a wire on the bulkhead disconnect) that once disconnected, your meter drops to "0-volts" then you've found the circuit with the short.

Now the tough step......start disconnecting things that are on that bad circuit, again one at a time. If you're lucky, you'll find some electrical part that has a short in it. Otherwise, you have to do basically the same thing to the wires. However, with wires, I try to disconnect both ends of the wire and use the Ohms setting on my meter and check for a ground in sections. For example, if you find a short in the fuel level sending unit circuit, I would disconnect the wire at the fuel sending unit & at the disconnect behind the kick panel then check that wire for ground (resistance not equal to "1"). Since that wire is NOT a ground wire, if my resistance is not "1" (meaning something close to "0") then there's a short somewhere in that wire. I then check that wire inch by inch for the problem OR just bypass that wire & run a replacement wire next to it as a replacement (not the correct way, but it works too).

moparjohnny · Sep 9, 2016

PurpleBeeper said:
This is basically how I track down my wiring problems. You obviously have a short to ground somewhere. I believe you need a good/professional multi-meter to run the current through it. It's just a matter of elimination & a wiring diagram is REQUIRED. You just start disconnecting circuits until your amp/voltage drop goes to zero.

Sorry to get basic.... for example. Disconnect the positive battery post, connect a good meter with one lead to the disconnected + cable & the other meter lead to the + of the battery, you should be showing something like 1-volt (or whatever) which is the current being lost to your electrical short. Then, one at a time, you disconnect circuits. For example, pull fuse #1 and see if the 1-volt on your meter is still there. If yes, put fuse #1 back in & pull out fuse #2 and so on. If none of the fuses being pulled make your meter drop to "0-volts", then start disconnecting wires at the bulkhead disconnect....again, one at a time. Once you find a circuit (either the fuse or a wire on the bulkhead disconnect) that once disconnected, your meter drops to "0-volts" then you've found the circuit with the short.

Now the tough step......start disconnecting things that are on that bad circuit, again one at a time. If you're lucky, you'll find some electrical part that has a short in it. Otherwise, you have to do basically the same thing to the wires. However, with wires, I try to disconnect both ends of the wire and use the Ohms setting on my meter and check for a ground in sections. For example, if you find a short in the fuel level sending unit circuit, I would disconnect the wire at the fuel sending unit & at the disconnect behind the kick panel then check that wire for ground (resistance not equal to "1"). Since that wire is NOT a ground wire, if my resistance is not "1" (meaning something close to "0") then there's a short somewhere in that wire. I then check that wire inch by inch for the problem OR just bypass that wire & run a replacement wire next to it as a replacement (not the correct way, but it works too).

moparjohnny · Sep 9, 2016

is your alternator charging your battery?

Mike67 · Sep 9, 2016

Most DMMs have the capability of reading dc amps, even the cheap ones...not to oversimplify but on dc amps the meter is placed in series ( in line) so the current flows through the meter, not in parallel ( t'ed).

Billccm · Sep 9, 2016

If you have a service manual, or can get details on your alternator to regulator wiring, you can simply ground the alternator field and should have FULL charging-if not, it's in your alternator, if so, then I would focus on the regulator and associated paths. I would perform this first as I assume you do not have 'leakage', but rather a battery not charging by your description. Am I correct here?

Keep in mind that the ammeter is in series with the regulator, and it's connection, or the ammeter itself can be a cause of battery charging issues.

Provide more details as I do not want to send you down the wrong path.

mopar_man · Sep 9, 2016

First check I would do is remove large or the hot wire on altenator.and check the draw at the battery then . if still not fixed, pull the hot cable from the starter relay that's bolted on the firewall . . if not fixed . reach up under the dash and see if you can disconnect your ignition switch . Your ignition could be worn and leaving something powered up causing your battery to drain . After those three tests , get into the fuse block and do as the other guys have said , if not found then you have to get into the harness plug at the fire wall . I believe all current goes through the amp gauge on a 66 , not sure about gas gauge going to the trunk . It's just a matter of elimination especially after you get to the firewall plug .

T-Man1971 · Sep 10, 2016

Thank you all for replies. I try to find leakege in wiring harness today. Thx Mike67 for your advice. I let you all know later. Thx :thumbsup:

Billccm · Sep 10, 2016

Okay, so if it is truly 'parasitic draw', you can troubleshoot as recommended here. One method I use is a test lamp. Start with the test lamp in series with the battery positive cable; does it light with the key off? If yes, then keep the lamp in place at the battery, and proceed to pull one fuse at a time until the lamp goes out, or glows very dim. That fuse is the branch that needs investigating.

Obviously your draw is not a short to GND, or you would have fuse blowing.

T-Man1971 · Sep 10, 2016

I founded the leak. There was an extra ground gable behind the dash. It was connected wrong place. I removed it, and leak is gone. But i still check rest of harness. :thankyou:

Battery still losing power/current

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