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Discussion Starter #1
My wife's car is out of commission and my truck just started acting up. I know the battery is old and week but it has a parasitic draw.
A couple of months ago it wouldn't start so I cleaned up the battery terminals, charged the battery and was back in business. I figured I would probably need a new battery next winter.
I did check to see if it was drawing anything at that time and it wasn't.
It wouldn't start this morning, Now it draws 12v.
I disconnect the alternator, unplugged fuses one at a time, even disconnected the starter and solenoid wires. No luck.

Will probably take it into the shop tomorrow? I have always worked on my own cars and would like to fix it myself.

Any ideas?
Thanks
 

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After years of charging and testing batteries only to get the customer telling me it was dead the next morning, I developed this method of testing. Charge the battery fully, then turn on the headlights. If the battery is good the headlights should stay on more than 40 minutes before the voltage drops below 12 volts, if not the battery is bad and needs replacement. This comes from playing golf and leaving the headlights on, after two hours the motor will still start (9 holes). After 4 hours the battery is dead and will need charging to work. This is a new battery. Every time it goes completely dead the life of the battery is reduced. I have even seen them charged with reversed polarity, where positive was negative and vice versa. After 4 years every battery is suspect and this test, charged fully then headlights on, while measuring the voltage drop will prove it is or is not the battery.
 

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Discussion Starter #4
You need to confirm you are having a parasitic draw measuring and comparing the amps being drained
I charged the battery and the meter said 12.5. I hooked up the meter inline between the negative terminal and post and it reads 12.5
 

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08 Toyota Camry 2AZ-FE R9K Tuned
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I charged the battery and the meter said 12.5. I hooked up the meter inline between the negative terminal and post and it reads 12.5
You are only checking for voltage. Amps is the current, amps shows how much power you are drawing. Voltage is I guess a constant and while it will change it will generally be at 12 volts. You need to determine how much amps is being drawn.
 

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boulderskies
2006 Tacoma
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for what its worth, in my experience, a healthy battery will show just over 14 volts. it seems to me, your battery is on the way out. its probably not a draw at all. just change the battery out and get on with it....((i just replaced a battery cuz the starter sounded weak each time...it must have been going dead for a long time and i musta got used to it cuz now, it FIRES right up-big difference))
 

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My test works every time and if you ignore the advice, you can waste a lot of time AND money. Battery test good, then it's totally dead the next morning, pissed off customer. No parasitic draw will kill a good battery overnight. Charge, test, replace, or go further in diagnosis. Otherwise you are wasting time and sometimes money. I took a fully charged battery, stuck it in the floor and ran an 8 track tape player for 6 days on that same battery (without recharging) on a vacation, then cabled it to the car battery and recharged it for another long term round of music until it had the time to hard wire it to the car. Surf board racks got stolen constantly so I brazed mine to the drip rails, ground them off when I sold the car, after touching up the paint.
 

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08 Toyota Camry 2AZ-FE R9K Tuned
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@tvtrader19
I don't know about the so called "place a bulb inline with the battery terminal" method, I guess it can work but it was not something I was taught. If anything, that method sounds like @Old Mechanic method of leaving the head lights on for 40 minutes. You read the amps and see how high it is. Open the door and assuming your dome light or door light or other component connected on the circuit turns on you will see the amps rise. Once you close it, it will lower. Using this method, you have to determine whether or not you have a parasitic draw or not. This is when you can pull fuses one at a time to watch the amps drop. If it drops, then perhaps you have a drain or you took the fuse out of a component that always has power.

The lower the amps, the better. Then again it's been a long time since I've searched for a parasitic draw.
 

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My Other Truck
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I don't know about the so called "place a bulb inline with the battery terminal" method, I guess it can work but it was not something I was taught.
It's pretty rudimentary, but it's a method I have used at times (for the record, I have a multimeter). It can be a quick easy way to determine which circuit is draining the battery.
 
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