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Battery being drained while key is off
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Author:  ESP47 [ Sat Apr 24, 2010 2:34 pm ]
Post subject:  Battery being drained while key is off
I have to disconnect the battery on this 67 Valiant every time I park it or else the battery will be completely dead the next morning. I have a volt meter so where should start going about troubleshooting things? Upon visual inspection all the bulbs are good and none of them are on when the car is shut off. I checked the voltage from the coil and alternator and everything checks out ok there. Not really sure where else to go about finding the problem though.
Author:  SlantSixDan [ Sat Apr 24, 2010 2:45 pm ]
Post subject: 
Does the car have a glovebox light or a trunk compartment light? Those are prime suspects for hidden current theft. The thing to do is put your voltmeter between the battery positive terminal and the (removed) battery positive cable clamp, and then remove fuses one at a time until the voltage drops off -- then you've found the circuit that's active when the ignition is off.
Author:  Charrlie_S [ Sat Apr 24, 2010 5:21 pm ]
Post subject: 
Another posibility is a bad alternator. If the alternator has a shorted diode, it will still charge (not at full output) but drain the battery, when not running.
Author:  ESP47 [ Sun Apr 25, 2010 9:23 am ]
Post subject: 
Thanks Dan I'll get on that today.

Charlie, is there a way I could test that?
Author:  ESP47 [ Sun Apr 25, 2010 3:01 pm ]
Post subject: 
I ran the test Dan recommended and it was the tail light fuse that caused the voltage drop. None of the tail lights are on at all when the car is off. Everything works correctly except the flashers don't work at all. Not on the outside and not on the instrument cluster either. Could this be the culprit? The FSM says change the

I only have a 71 FSM and it says the flasher is located on the "instument panel support". Since this is a 67 Valiant I'm not sure if these directions apply. If this is correct for 67 as well, I have no idea what the instrument panel support is and I've never even seen an old flasher either. Do they look like the new ones that kind of look like a little plastic cylinder dome with plugs coming out of one end?

Even if the flasher was the reason for the flasher lights not working, would that even be causing the battery to get drained? I'm assuming if the flasher went bad it would just cause an open in the circuit.
Author:  Slanted Opinion [ Sun Apr 25, 2010 4:25 pm ]
Post subject: 
The tail light circuit is not the one I would have expected to cause a battery drain.
But anything is possible on these old cars.

Let's test your detective work to see if you indeed found the culprit circuit. Pull the tail light fuse and see if the battery now stays charged overnight.

- Mac
Author:  KBB_of_TMC [ Mon Apr 26, 2010 10:44 am ]
Post subject: 
You can track down even tiny drains using a 12V test light and an inexpensive digital multimeter (DMM). First, use the 12V light *in series* with the ground - if it lights up when everything is supposed to be off, keep disconnecting circuits until the light goes out. You need not disconnect the battery as you're unplugging stuff, as even a short will have its current safely limited by the test light.

Just to be safe, though, I'd disconnect any digital electronics (fancy radio, computer, etc.) before I started.

If the drain is too small for that, a DMM can directly measure the current drain - beware that you don't overload the meter, as the cheap ones can easily fry despite their internal fuse. For really small drains, you use the meter in voltage mode - it acts like a ~M ohm resistor.
Author:  ESP47 [ Mon Apr 26, 2010 4:34 pm ]
Post subject: 
Mac, that could turn out to be a very expensive way to just test something lol

I only had a couple minutes to mess with it on my lunch today but I did notice when I push the door switch in to turn off the dome light, the volt meter drops voltage. Which tells me it has nothing to do with the tail lights and probably something to do with the dome light. Now the dome light turns off with the door shut so I'm assuming that the door switch is some how shorting the circuit out directly to ground which is then draining the battery. Because even if the switch was keeping the dome light on so dim that you couldn't see it or if it just gave off some heat....that really shouldn't be enough to drain an almost brand new battery down to nothing the next morning.
Author:  Mark Mallett [ Tue Apr 27, 2010 3:56 am ]
Post subject: 
Did you pinpoint the problem yet? You say you are measuring voltage to find the issue when you should be measuring amperage.

If you have a decent meter it should have a direct current amperage scale. Set the meter to the highest scale for DC amps and plug the leads into the appropriate jacks.

Take the red positive lead and connect it to the battery negative terminal, connect the negative black lead to the cable that normally resides on the negative battery post.

The number the meter displays is the total amperage the electrical system is consuming. This reading should be very low if it is not you can now start to look for the problem.

Since all visual items are off (lights) you will have to narrow it down - try unplugging the fuse for the tail lights again - if your amperage reading drops to an acceptable level you have found the circuit causing the issue.

A wiring schematic for the circuit in question will help immensely at this point. Since all the lights on this circuit are in the off state I would suggest you are looking for a damaged wire that provides positive voltage to a load - it could be damaged and touching the chasis (your negative).

It could be bare and completing a circuit through dirty and or rusty metal thus creating a load.

Good luck :) Feel free to PM me if you need further help or post a more detailed account of what you have checked. We can find it!

Edit - just did a quick look on the net for battery capacity to give you some perspective on an acceptable overnight load for the battery. Check you battery label for a reserve capacity in minutes - I looked at mine and it has a 90 minute reserve when fully charged. This capacity rating presumes that a fully charged good battery will deliver 25 amps effectively for 90 minutes before it will drop below and acceptable operating voltage (10.5 v).

So with a little math we can now put your problem in better perspective. Using my batteries spec we have 90 minutes (1.5 hours) at 25 amps.

1.5 hours x 25 amps = 37.5 amp/hours

So my battery can deliver 37.5 amps for 1 hour or 1 amp for 37.5 hours before it will start to approach a point that it will deplete the battery below a level that will start the car.

With all this in mind I would suggest that you are looking for a constant load with car idle of less than 1 amp.

Peace :)
Author:  walpolla [ Tue Apr 27, 2010 4:14 am ]
Post subject: 
Hello,
If you do'nt have a wiring diagram,you will find one here

Just select your model and year,and done.

regards,Rod :D
Author:  ESP47 [ Sun May 30, 2010 10:28 am ]
Post subject: 
Ok now the problem seems simpler but I still don't know what to do.

The brake lights are now always on. How do I go about correcting this?
Author:  Mark Mallett [ Sun May 30, 2010 3:15 pm ]
Post subject: 
There should be a switch located near and actuated by depressing the brake pedal - I would start there :)
Author:  DusterIdiot [ Sun May 30, 2010 3:53 pm ]
Post subject:  Yep..
Quote:
The brake lights are now always on. How do I go about correcting this?
Like mark said, but in more depth:
Open door and crouch down so you can look under the dash, follow
the brake pedal lever up to where it's bolted into the dash. If you look there will be a little white "plunger with a wire coming out of it, that's teh switch, undo the nut and adjust as needed, have a buddy watch the rear brake light as you adjust to see if they go on when you depress the pedal, and off when it's off...

I would also suggest feeling the top of the plunger to see if it's work at an angle, the one in my mom's valiant wore that way and the plunger would "slip off" one side of the pedal and stay on...

Good luck,

-D.Idiot
Author:  ESP47 [ Sat Jun 05, 2010 6:28 pm ]
Post subject:  Re: Yep..
Quote:
I would also suggest feeling the top of the plunger to see if it's work at an angle, the one in my mom's valiant wore that way and the plunger would "slip off" one side of the pedal and stay on...

Good luck,

-D.Idiot
That was the problem here. I couldn't get in there enough to bend the bracket to move the plunger straight on. So what I did was grind down and then put a washer on the brake lever next to the contact area it so now it pushes the plunger back in and shouldn't slip off for a long time. If it seems like it is going to slip again at some point, I'll just put another washer on to widen the contact area. That's why sometimes the brake lights were on and sometimes they weren't. It would catch on there half the time and the other half it would slip off.

So I fixed that and then disconnected the positive cable. Took a voltmeter and attached it to the + battery terminal and then to the positive cable as well. When I took the tail light fuse out, my voltage dropped to 3.5v. Back in and it goes to 12.6v. None of the other fuses caused a voltage drop at all when removed. That means I still have something pulling current on that circuit huh?

Image
Author:  wjajr [ Sun Jun 06, 2010 5:12 am ]
Post subject: 
ESP47:
That means I still have something pulling current on that circuit huh?

Yup.

You will find that the draw is from a circuit that is energized at all times, independent of ignition switch position, such as driving lights, cigar lighter, 4 way flasher, interior lighting, horn etc.

Systematic, elimination of sections of the wire harness by unplugging select connectors will narrow your search. Get out a wiring diagram to help plot your activities. This is slow methodical work, make notes, and record which devices & circuits have been tested as you proced.

Perhaps you could remove driver’s side kick panel as a first step, disconnect the multi wire connector contained within, that feeds the rear wire harness, and the other connections located there, one at a time. This would eliminate all wire & devices from that point to the rear bumper & possibly the headlight floor mounted dimmer switch (don’t remember it that is in there or not).

At the steering column near brake peddle disconnect the multi wire connector that feeds the directional light switch residing behind the steering wheel. There is a lot of interconnection of functions in this switch, and opportunity where wires chase up along the steering shaft to chafe causing a low grade short.

Using a FSM as a guide, so you know what section of electrical system is supplied: unplug one at a time, the three eight wire plugs on the engine side of the bulkhead connector checking for current draw each time.

Hopefully this will narrow the hunt.
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