Current draw on battery

[Michael J.]

I have noticed my '67 L71 coupe (it has been out of my hands for many months, so not sure what all could have happened) is experiencing a battery drawdown while sitting with nothing but the clock running. I am also noticing my rear tail lights are not blinking as they should, the inside lights do not blink on the turn signals or emergency flasher like they should, not sure if this is the same problem or related. Is there any trouble shooting I can do to find the current leak on the battery? Thanks for any tips.

[Stuart F.]

Re: Current draw on battery

Leaky Diodes in the alternator? Perhaps not an amount to be this, but just something to throw nto the hopper for you to check. My battery went stone dead because of one diode, and that was preceded by a broken pigtail wire connector.

Stu Fox

[Michael J.]

Re: Current draw on battery

Thanks Stu, that is a possibility. But would a diode be bad and the charging system still working properly? My charging system is working great, charges it right back up to 100% and isn't a problem when lights are on, etc.

[Tim E.]

Re: Current draw on battery

Mike - It's very likely the two problems are related. Some things I'd suggest:

1. Does your battery remain fully charged when you disconnect it with your battery disconnect switch? If so, then you know that some circuit is causing a discharge.

2. Assuming the blinking problem is related to the battery discharge, pull fuses one by one (or 2 by 2, or...) to see if eliminating those circuits restores your flashers to normal. If it does, then at least you know which circuit has a short, a bad ground, or corrosion on a contact surface (breaker point type contact or a wire terminal connector).

Any debris that can carry an electric current can provide a path and a leak including "carbon traces". Carbon can be deposited (like inside a distributor cap) and cause misfires when the spark intended for one cylinder goes to another.

I suspect the flasher problem is being caused by either too much or too little resistance in the light circuit. The same principal that causes your blinkers to speed up when a light bulb burns out. Flashers are carefully designed for just the right amount of resistance created by 2 bulbs, 4 bulbs, etc. A short or corrosion in that circuit changes the resistance value.

See if you can isolate the problem circuit first by pulling fuses....effectively taking that circuit "off line".

Tim

[Michael J.]

Re: Current draw on battery

Thanks for the tips Tim, I will start the tests in the morning. The battery goes down to 80% or 12.5 volts on my meter after sitting for a day hooked up, it is steady at 100% without being hooked up. Great to see you and Carla at the Regional too, hope you make it to Tucson.
Mike

[Michael H.]

Re: Current draw on battery

Check your glove box light as well maybe its staying on all the time.

[Michael J.]

[Gene M.]

Re: Current draw on battery

Michael,
Easy check for diodes in the alternator, just remove positive terminal on the alternator. If no discharge you found issue. The one by one fuse insertion will disclose a circuit with issues. Only one fuse installed at a time. A meter on battery as suggested works to show current draw.

[Robert D.]

Re: Current draw on battery

If you disconnect the negative battery cable and place an ammeter between the neg cable and neg pole on the battery the reading will tell you if you have a draw usually a normal reading will be up to 40-50 milliamps from things like the clock if it is greater than that the draw is to great and will drain the battery more rapidly. then you can remove fuses to see which cicuit its from and narrow it down to trace the draw
Good luck
Bob

[Michael J.]

Re: Current draw on battery

Thanks for all the help guys, situation is now stable, and no draw on the battery in over 24 hours of monitoring.

[Dennis O.]

Re: Current draw on battery

Just curious; what, if anything, did you do?

[Leif A.]

Re: Current draw on battery

Thanks for all the help guys, situation is now stable, and no draw on the battery in over 24 hours of monitoring.

Michael,

What did you find was the cause of the drain?

Leif

[Michael J.]

Re: Current draw on battery

Well, it was a bit odd. After checking the diodes for drain, not there, I switched to pulling fuses. The first I pulled was to the interior lights just to double check. You will notice above Michael Hanley asked about the glove box light. I had opened the glove box early on a couple of days ago when I first noticed the problem, and saw no light on even open, so thought it was either burned out or the switch was malfunctioning, but moved on since I was focused on the drain. But when I pulled the fuse, the drain stopped. So I looked around the other lights and saw no issues, but when I put the fuse back in to check the glove box (thought I would replace the bulb), when I opened it I noticed the bulb, though not lit, was hot. So I turned the lights off in the garage, closed the glove box door, and saw the light was on when the door was closed, but not when it was open. There was a short in the socket that somehow got connected when the door was closed, but not when it was open. Very strange, but glad I double checked it. Sometimes it is the simplest things, just not exactly the malfunction you were thinking of.

[Leif A.]

Re: Current draw on battery

Nice job, Michael. Good sleuthing

[Michael J.]