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Pulsing battery draw ?

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AldeanFan

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My 2005 tundra was dead this morning,
Last drove it two days ago and it started and ran fine then.

I though it may be dirty battery terminals so I cleaned them tonight but noticed when re connecting I got an arc from the cable to the post, keys in my pocket and doors shut.

I put my test light between the battery post and the ground cable and it flashed.

What would cause a pulsing battery drain?

The truck is bone stock, 90,000km and very well maintained.

Tomorrow I'll start pulling fuses looking for the culprit.
At least I have shiny clean terminals.
 
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BillK

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Mark,

It might be normal. Most modern vehicles have modules that remained powered up for a while after you shut the engine off. Some modules can take an hour before they power down. Others can power back up, for instance the emissions EVAP system test can come on at any time.

I am only saying this so you don't waste a lot of time chasing a problem that does not exist. If you don't have a service manual you will never know.

That being said, the 16 or so month old AC Delco battery in my Tahoe left me sitting about a month ago. Almost identical situation, mine was fine one day and would not start the next morning. I did every test possible and decided it had to be the battery, which it was. New battery under AC Delco warranty and all is well.
 
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jkwilson

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Very normal to get a spark when reconnecting the battery. Many things draw power with the key off, and even wiring causes some current to flow.

Flashing may be a result of something trying to power up and resetting because the test light isn't allowing current to flow.
 
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GTA Matt

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Leave the test light in the toolbox, not the proper tool for draws on modern vehicles. Use a dvom to get the actual current draw on the system AFTER the truck has been sitting for a half hour or more. Lots of tutorials on how to do this out there. Once you have verified there is an unacceptable draw, simply do a volt drop across the fuses to determine which circuit(s) have current flowing. No need to pull fuses, much faster and simpler.
 
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theoldwizard1

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Common in most modern cars. Some electronic module wakes up and looks around to see if some task needs to be done.

GTA Matt said:
Leave the test light in the toolbox, not the proper tool for draws on modern vehicles. Use a dvom to get the actual current draw on the system AFTER the truck has been sitting for a half hour or more. Lots of tutorials on how to do this out there. Once you have verified there is an unacceptable draw, simply do a volt drop across the fuses to determine which circuit(s) have current flowing. No need to pull fuses, much faster and simpler.
Click to expand...

100% correct !
 
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pepi

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Woodstock, GA
jkwilson said:
Very normal to get a spark when reconnecting the battery. Many things draw power with the key off, and even wiring causes some current to flow.

Flashing may be a result of something trying to power up and resetting because the test light isn't allowing current to flow.
Click to expand...

Connect the positive lead first then the ground........... no sparks.

Disconnect ground first
 
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JJThrasher

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Get out the DMM, hookup for amps in series with the battery cable, have everything off, doors closed, key removed, disconnect under hood light if equipped, wait a couple minutes for your reading to stabilize, and you should be under .1 Amps.
 
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nadogail

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The radio and alarm systems in my van are constant parisitic draws on the battery.

Frequent, almost daily, driving charges the battery sufficiently to support them. Because I drive the van infrequently, I use a solar panel battery tender to keep the battery charged.
 
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jkwilson

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pepi said:
Connect the positive lead first then the ground........... no sparks.

Disconnect ground first
Click to expand...

Not true. You get sparks regardless of which order you connect. Current actually flows out of the negative terminal of a battery. Electrically there is no difference in connecting or disconnecting either wire.

The reason for doing the positive lead first is to prevent shorting it to the grounded frame with the tool you are using.
 
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A

AldeanFan

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Thanks for all the great insights,
Turns out the battery was bad.
The pulsing draw was the truck trying to honk the horn and flash the lights, probably because I unlocked the door with the key since the battery was too low for power locks.

More details,

Last night I had a few beers after dinner and when I went out to lockup the garage I figured I'd clean up the battery connections and put the charger on it overnight. I did connect the positive first and the negative last and got the arc off the negative. The test light was handy so I grabbed that first. I was ready to pull out the meter but it was getting late so I put the charger on, grabbed a fresh beer and locked up the garage.
This Morning when the battery was up to 12v and I was sober and had the ambition to get out the multimeter, the draw was gone after I unlocked the truck with the key fob, but the battery tested bad so off to the store for a new battery.

I should have remembered, last month I was bringing groceries in and my little girl jumped in the front seat of my Pontiac to honk the horn, she also turned on the headlights. A few hours later I went out to wash the car and the battery was almost dead so I hooked up the battery charger and went off to do something else, 15 min later when the battery has some juice the car started blowing the horn and flashing the lights, just like the truck.
 
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