Car won't start

'01 Tiburon
Service dealer tests – battery & alternator good, and no predatory current draw
fully charged / 24 hours / car starts
fully charged / 36 hours / needs a jump
fully charged / 48 hours w. positive cable disconnected / car starts (yes, I reconnected the cable)

This all happened recently, and is getting worse
I’m open to suggestion

If the battery tests good. but is drawn down the longer it’s connected to the vehicle it means there’s a parastic current draw somewhere.

Do you know what procedure was used to test for a parasitic current draw?


There should be some kind out parasitic draw to pull down the battery like that. It will be slight if it holds for 24 hours, but fails at 36. I’d have the draw test performed again. I think the last test mentioned rules out a bad battery. Have you pulled out interior light bulbs yet?


how old is that battery?

More to the point, what’s the specific gravity of each cell of the charged battery?

Disconnect the battery’s negative terminal (safer than disconnecting the positive), touch the ammeter’s (in the 10A range) negative lead to the battery’s negative terminal, its positive lead to ground: what’s the draw? Mine is about 6 milliamp - the power to run the clock. I suppose it could be over 10 amp, but I think that would discharge the battery in 24 hours.

If you have a multimiter and can do basic electrical troublehsooting, here’s how:

That’s the old method for testing for a parasitic current draw. Todays vehicles have computers/modules that can fail to go to sleep when the vehicle is shut off. And if you disconnect the battery you force the offending component to go to sleep so you won’t see any current draw.

Here’s the proper method for testing for a parasitic current draw on todays vehicles.


That’s a good informative link you posted there @Tester. I really liked the tip about making a current loop multiplier. Thanks.

Here we go again . . .

I, for one, am able to carefully hook up my multimeter WITHOUT breaking the connection, so to speak

On top post batteries, in any case

I’m having trouble understanding exactly what the OP is describing is happening.
It sounds to me like the car is starting intermittantly with the battery fully charged. That would suggest a whole different problem, perhaps a starter.

Exactly what is happening when you try to start the car?
How many miles are on it? Has the scheduled maintenance been kept up to date?

Sounds to me like OP is saying the battery dies quickly when it’s connected. It’ll retain enough charge for 24 hours to start the car, but not for 36 hours, at which time it needs a jump start.

OP then recharged battery and disconnected the positive terminal to see if the battery would hold charge while disconnected. After 48 hours OP reconnected the terminal and was able to start the car.

Ergo the battery is holding a charge when disconnected, but when connected there’s a parasitic drain that’s running it down in less than 36 hours.

That’s my interpretation. Correct me if wrong.

PS…thanks Tester for the modern test protocol. My vehicles were built before F.R.E.D.s were invented. :slight_smile: