Hi all. My daughter has a 2020 Toyota Highlander 6 cylinder. Most of the time it’s fine. But once in a while the battery is dead. And most times it was fine the day before. What can cause that? We jump it and it is fine for a month or so. Then it goes dead. I put in a new battery, but it still happens. Anything I should check or replace? Thanks for any help.

 

There are a few possibilities
- The battery is sometimes not getting charged -- seems unlikely
- The battery is being discharged by something when everything is shut off ( quite possible)
- The battery is NOT really dead -- one of the main wires sometimes goes open and nothing happens because the battery is basically not connected

Battery being discharged by something does happen and you can do something easy to see if that's it. Get a battery switch (fits on the battery) and put it in the off or open position EVERY time you stop the car for any period of time. If that stops the problem you can find somebody to troubleshoot it. It's intermittent so it will be a pain.

Other possibilities need to be checked by somebody who knows what they're looking at. Most can be checked with a simple meter, but you have to understand what you're seeing ( For the record, Harbor Freight has an adequate meter for about 7 or 8 bucks)

It's not usually a matter of just replacing something. Troubleshooting auto power circuits isn't usually that hard, but as I said, you need to know what you're looking at. You can get a book from the library and watch several of the million youtubes (watch several because some of them are just wrong).

One simple thing that you can do is get a cheap meter and read the battery voltage frequently. Read it right at the terminals. Put the red wire on the plus and the black wire on the minus. Put it on DC volts and the 20 volt scale, It should read over 12 when the car is just sitting there. It will go down to 9 or 10 while the car is being started -- but shouldn't go below that,.
It will jump up to 13.5 or more for a while because the generator will be charging the battery. It should read nearly as high in the morning before you start it for the first time as it did when you shut it off.

Your daughter can dp this as well -- it might save her from trouble some day.

hj

 

I would carefully check and clean the wiring carrying the heavy battery-supplied current first. After that I'd look for any sort of excessive parasitic draw but that does seem somewhat unlikely as you say this problem is intermittent---that alone points at loose terminals somewhere in the battery and starter circuits.

 

if the car does a lot of short hops, the alternator may not charge the battery enough to compensate for power used to start the engine.
i had that problem with my 99 crown vic.

 

I questioned her about the trips she takes. 15-20 minutes to drop off the kids at the nanny in the morning. Then back home. No pick up at night. Her husband does it on the way home. Other places only once in a while. The battery is new. The cables are clean. I will check the connections on the starter and alternator and ground next and report back. Thanks for the help.

 

So the wires to the starter are tight. The alternator wires are tight and the ground is tight. Can there be something like the fan not turning off when it is supposed to? Or can the alternator not always charge?

 

glove box light, and hood light are always my top two suspects when everything else checks out.

 

Good ideas. I will check them. Thanks.

 

True---I had an '85 Pontiac 4 door with trunk lamp triggered by the trunk lid being raised--it failed leaving the 1156 bulb on long enough to kill the battery. It was only through testing for a parasitic draw I found it---never thought it could be the problem. :eel:

 

Call your Toyota Dealership to ask if there is a Recal for the general problem.

Maybe when she opens the Driver door to get out the systems don't shut off.
A defective switching there. Sometimes lights can also stay on with defective switch.
Check shutting off the key and not leaving the vehicle. Does the radio continue to play for an hour or all night.
Things like Radar Detector stay on plugged into the Cig Lighter of USB port.
Possibly check your LUC transmission valves ?
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1. Electrical Bugs: A programming error in the Engine Control Unit may lead to stalling.

If you’re a Highlander owner, check your Vehicle Identification Number (VIN) to see if your vehicle is affected by these recalls.
You can do this through the NHTSA’s VIN lookup tool

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My wifes car started to have battery problems. I changed the clamp to Lead and hooked the other wires up to it. no more problems. 4 years ago.
The main + battery cable clamp was crap where the Copper went into it. I cut it off and had enough cable Copper for the new post clamp.

 

Could also install a battery maintainer and plug that in. Even the smallest maintainer will do wonders for this stuff.
"family cars" are often having the doors opened a few times a day, which turns the lights on, and "wakes up" the vehicle. Some cars also "wake up" if the keys are stored too close. Could try hanging your keys up at the far side of the house.

 

there are no recalls on the highlander for electrical issues.
there are 5 recalls, but they are for passenger front airbag sensor defect that could cuse the airbag to not deploy, defect in front bumper cover causing it to possibly come loose after minor impact, software update on electronic stability control that may not turn on, incorrect placement of front seat trim cover that can cause side airbags to not deploy properly, and a fuel system issue with the ecu which may cause improper fuel delivery to engine when start/stop feature is used.

 

Well in a way it is fixed, or should I say no longer a problem. They traded in the car and leased a new one. She works from home and has groceries delivered. So she doesn’t drive far. They switched to a new Jeep. Oh well.
Thanks for all the help.