Battery resets when I turn off engine/pop hood


#1

I recently replaced a dead battery in my Lexus RX 300, and have noticed something weird which I’m hoping to get an explanation for (and potentially fix).

When I turn off the engine, sometimes the battery itself seems to disconnect.When I try to turn on the car at this moment nothing happens. However, when I press the button which pops the hood in the car and then try to start the engine, everything turns on fine (and my clock resets).

My guess is that something is loose near the battery, but wanted to share here to get some more concrete ideas of what is going on and how to address this.


#2

Before replacing the battery what was moved or disconnected in the effort to get the car started and/or diagnose the cause for not starting? Might there be a fuse box near the hood release.


#3

Since you just replaced the battery, open the hood, and try twisting the battery terminals on the battery posts.

If you’re able to twist either one, that’s a poor battery connection.

Tester


#4

The internal fuse is close to the hood pop lever, but I don’t think this was the issue.

Tester had it right - my battery contacts were lose, and the positive terminal wire was being shaken on/off the battery when I was popping the hood.


#5

I wouldnt go anywhere or do anything nor park the car in the garage until you figure this out. None of us here like to hear that power disconnect is being associated with the position of the HOOD… This strongly suggests that you either have loose batt terminals…which may have been indeed tightened to their limit yet are still unable to produce clamping force on either terminal…a very common occurrence. OR…the new battery is now taller than the old one and there is some sort of unwanted contact of the hood to battery…this is NOT GOOD and must be diagnosed immediately.

Sounds like your hood is applying pressure to either connection and allowing it to make contact (most likely the ground side since no fires have erupted as of yet)…and when the hood is released…this pressure is also released and no battery contact is present. This is bad for many reasons…Worst case is hood contact with the positive side and grounding out the battery… Fire is the next act in this scenario.

If you find that your positive clamp is unable to grasp the terminal…or the negative as well…they sell battery post adapters made of lead that basically enlarge the diameter of either post of the battery…which allows the battery clamp to grasp hold properly. They cost .99 for a pair ? Not ideal but they work when needed. Replacement clamps are hard to install correctly and it is a dis service to install those .99 c batt clamps in place of the factory ones currently installed.

The batt posts are actually different diameters…the pos batt post is fatter than the negative…just apply the post adapter to whichever one that needs it. You may find that you can only utilize half of the post adapter bec the whole thing is too big…adjust as needed, they can easily be cut and sized accordingly.

Please figure this out asap. Shouldnt be too hard to troubleshoot…but by all means…do this NOW.

Blackbird


#6

Considering the new battery is the exact same model as the previous one, I don’t think this is a battery height issue. Thanks.


#7

Loose or dirty battery connections are some of the most common electrical issues there are and such a simple thing to fix. Another common issue is over tightening the clamps which causes the clamps to stretch and that can make them unusable over time. If the connections are snug tight and clean it would be a good idea to then spray a sealer over them to prevent corrosion getting to them. You won’t have any further battery connection issues.


#8

@Nakura OK thats great…how bout the other items suggested ?

Blackbird


#9

Security system check, looks like the hood is part of the security system, Bad switch?

Testing the system 1. Open all the windows. 2. Set the system as described above. The front doors should be locked with the ignition key or wireless remote control. Be sure to wait until the indicator light starts flashing. 3. Unlock one of the doors from the inside. The system should activate the alarm. 4. Unlock any of the doors with a key or the wireless remote control to cancel the system. 5. Repeat this operation for the other doors and hood. When testing the hood, also check that the system is activated when the battery terminal is disconnected and then reconnected. If the system does not work properly, have it checked by your Lexus deale