Tuscon won't start after sitting a few days - battery is good

we have a 2005 Tuscon and it if sits for a few days we can not start it without a jump. everything that could drain the battery is off - radio, lights etc… Once we jump it with the little portable jumper it starts right up. the battery has been replaced and once it is jumped then it can be driven and re start that day after running errands etc…

There’s probably a parasitic current draw on the battery as the vehicle sits for an extended period of time.

In the past, before vehicles had computers and modules one would remove the negative battery cable and connect a test light between the battery post and cable to see if the light illuminated. And if it did, then fuses and relays would be unplugged until the light went out indicating what circuit was causing the current draw. This method of testing for current draw no longer works because it requires disconnecting the battery.

The computers and modules in todays vehicles can remain on or awake for up to an hour after the vehicle has been turned off. After that time these components then go to sleep or turn off. At least they’re suppost to. If the current draw is caused by a computer or module that fails to go to sleep, and when the battery is disconnected, this forces these components to go to sleep. Then when looking for a current draw at the battery none will be seen.

Instead of powering down these systems by disconnecting the battery and causing these components to go to sleep, a parasitic current draw is detected by measuring the voltage drop across the fuses. This indicates what circuit or module is drawing the current as the vehicle sits.

Take the vehicle to someone who knows how to test for a current draw using this method, and I’ll bet they’ll find out what’s causing the battery to go dead.


Tester…Thank you very much for taking the time to write this indepth explanation (for me anyway) of how this works.

I have one question though…Do you measure with the multimeter leads accross the fuses directly, or do you first pull the fuse out, since there’s not a wholo lot of room in there. Thanks again.

Thank you very much - will try this

Never check a fuse while it’s still installed in any circuit. If the fuse is dead you could still get a resistance reading through the circuit in the opposite direction.

Just my two cents but pulling the fuse is the same as disconnecting the battery at that particular circuit. If you pull the fuse then there will be no power to the components on that circuit.

If you have the pullout headlight switch, it’s possible for the switch to pull current. I have an older vehicle that the switch was draining the battery. By turning my headlight switch I make my dashlights brighter or dimmer. It also provides power to the overhead lights. I now rotate the switch all the way to the left and can feel it click into an off position. No more dead battery after sitting for a few days.

This explains how to test for a parasitic draw on todays vehicles. http://motorage.search-autoparts.com/motorage/Technical/A-new-approach-to-testing-parasitic-draw/ArticleStandard/Article/detail/660025