Years ago I had a similar issue. Turns out I put new trunk weatherstripping on and it held the trunk lid up enough to allow the light to remain on. Unless you get in the trunk and have someone shut it it's real hard to tell. I guess you could pull teh bulb and see if the battery drains.

Disconnect the alt.leads & see it could be shorted.

Read ....He has disconnected the alternator.

Working on a 78 Chrysler LeBaron. It's a low mileage car, absolutely stock and untouched, other than it has had an electronic ignition conversion to eliminate the Lean burn system.
So the issue is:
The battery will go dead in a day or so.

Brand new battery.

With the key off, doors and trunk closed, and checked to make sure no lights are on.
I pulled off the negative cable, and put a test light between the negative battery post, and the negative cable. The test light is bright.
I then pulled every fuse out one by one, and no change. Test light still on.
Disconnected various items such as alternator, electronic control box, wiper motor, power seat, and still no change.
Anyone have an idea as to what is drawing power?

Trying to shotgun electrical problems usually never ends well. Get a wiring diagram for your car. Based on that, start removing components one by one until the problem is found. I've been through this more than once and this typically has worked best for me.

there is a relay (3 wires) for the alternator, under passenger fender, has battery voltage at all times, unplug that

I'll check that. Thanks for everyone's input.
The owner bought the car recently from an estate, so he doesn't know much about it. The car is very low mileage and in excellent untouched condition.
The digital clock does not function though, so I do wonder if that is possibly drawing power

My bad missed that.

I'll check that. Thanks for everyone's input.
The owner bought the car recently from an estate, so he doesn't know much about it. The car is very low mileage and in excellent untouched condition.
The digital clock does not function though, so I do wonder if that is possibly drawing power

I've had aftermarket voltmeter gauges drain a battery also. If it has an aftermarket one, I'd check that.

[quote=demon]

You can't check voltage drain like that. The minute you put the leads on the post and cable it completed the circuit through the light bulb. It'll read 12 volts too if you use a meter hooked up that way. You need to check for amps.

I disagree, in a non automotive situation try to get a bulb to light when its connected negative to negative.

In the case above think of the bulb as acting like an amp meter as it will illuminate as a current flows through it. It is connecting to positive though the device that is using the current.

Well as a union electrician I can tell you are mistaken. It is not going negative to negative. The positive cable is still hooked up. All you're doing is taking off the negative cable and hooking it back up with a light bulb in it. The bulb itself is load. Unless you unhook every harness off the battery it will light the bulb.

[quote=demon]Working on a 78 Chrysler LeBaron. It's a low mileage car, absolutely stock and untouched, other than it has had an electronic ignition conversion to eliminate the Lean burn system.
So the issue is:
The battery will go dead in a day or so.

Brand new battery.


I pulled off the negative cable, and put a test light between the negative battery post, and the negative cable. The test light is bright.


You can't check voltage drain like that. The minute you put the leads on the post and cable it completed the circuit through the light bulb. It'll read 12 volts too if you use a meter hooked up that way. You need to check for amps.

Well as a union electrician I can tell you are mistaken. It is not going negative to negative. The positive cable is still hooked up. All you're doing is taking off the negative cable and hooking it back up with a light bulb in it. The bulb itself is load. Unless you unhook every harness off the battery it will light the bulb.

If you don't believe me go out to the garage an disconnect your negative cable and then get out a volt meter and put 1 end on the battery and the other on the disconnected cable. The meter will read 12 volts.

AH, Moparts strikes again! It happens with nearly every question concerning an electrical problem.

We have competing experts saying the other guy is wrong and his testing methods won't work, but mine will.

Is there any wonder why non-electrical people are confused about electrical problems? I've done a lot of automotive electrical repairs, but you guys can confuse me.

The experts argue with each other on how its suppose to be tested and figured out, and all the guy wants to to solve his problem. Who is he suppose to believe?

How about, if YOU have actually SOLVED the particular problem on a similar car the OP has, write a step by step process. If you personally have not solved the problem, don't post. This should not be a location to test theory.

Answer a DC test light is a tool with a normal open circuit that needs voltage to close to turn on light.

AH, Moparts strikes again! It happens with nearly every question concerning an electrical problem.

We have competing experts saying the other guy is wrong and his testing methods won't work, but mine will.

Is there any wonder why non-electrical people are confused about electrical problems? I've done a lot of automotive electrical repairs, but you guys can confuse me.

The experts argue with each other on how its suppose to be tested and figured out, and all the guy wants to to solve his problem. Who is he suppose to believe?

How about, if YOU have actually SOLVED the particular problem on a similar car the OP has, write a step by step process. If you personally have not solved the problem, don't post. This should not be a location to test theory.

I saw the reply's from some people I respect on here and decided I needed to do more research. I'm always willing to listen and learn and I learned something new today.

Since 99.9% of my work is AC I needed to do some checking. Here's what I found was causing the difference of opinion.

Answer a DC test light is a tool with a normal open circuit that needs voltage to close to turn on light. So no it will not complete a circuit without voltage. Where an AC test light is just a closed circuit and will complete the circuit. ( yes I know it's a light bulb in a socket but that's all an ac test light is and i don't ever use them. I always use a meter).

The photo's show the ohm's and open circuit on the test tool.

I believe this source is still good info and would use a meter because almost ever car now has some draw (Clock,memory on radio & drivers ect.) that could turn the light on partially. Be sure and put the red lead in amp hole and set meter to DC amps. https://www.wikihow.com/Find-a-Parasitic-Battery-Drain

nothing to add, but i have the exact test light [black handle, serrated bulb case, wire color/size and clamp] you show, and have had that item for almost 55 years.

I kind of skipped through all of the posts and suggestions but I have a question for the OP. In your first post you state it's a new battery, did you have this battery draining issue before you put a new battery in? What if it's a bad (new) battery? Just saying.

now that we've stopped peeing over the fence has the OP found the issue yet ?

I kind of skipped through all of the posts and suggestions but I have a question for the OP. In your first post you state it's a new battery, did you have this battery draining issue before you put a new battery in? What if it's a bad (new) battery? Just saying.

Yes, the owner changed the battery because of it draining, and it still drains with the new battery.
He purchased the car from an estate recently, so we don't know any of it's previous history. But it is in very nice original condition

Yes, the owner changed the battery because of it draining, and it still drains with the new battery.
He purchased the car from an estate recently, so we don't know any of it's previous history. But it is in very nice original condition

I parted a 71 Dart years ago that had a fried underdash harness. I kept it for redoing the one in my 70 and when I opened up the fried one, I found the brake warning circuit wired wrong.
The downleg wire after the light was only connected to the e-brake switch, but the low fluid circuit was joined at the hot side.
Imagine trying to troubleshoot a hot wire smell that only occurs when the brake fluid is low, much less connecting those two dots!