Toyota Tacauma 2000

My battery drains during very cold nights and very hot days. Alternator checks out fine and battery has been replaced. Summer months of August and now the cold months affect it.???

If the battery and chargung system are good, you have a parasitic drain. Short of checking with an ammeter, the best bet is first to check to see that all lights are off including the glovebox and console box if you have those. If you have a cap with a light, be sure to check that, and check your license plate lights.

If you have no lights on, then attach an ammeter under the hood and remove fuses until the drain stops. If you’re unfamiliar with the measurement of current, you may need to solicit the help of a friend.

Another option is to disconnect the battery and check the circuits for a high resistance short to ground. The most common sporce is in the wiring harness that carries the circuits for the power door locks where the harness goes from the main chassis to the door locks. It goes through framework holes and bends there every time you open and close the door, and it remains hot when the car is shut down. A chafed or fractured insulation there can cause a high resistance short to ground, which can become a parasitic drain.

You could also just remove the fuses for all unneccessary circuits and see if the problem stops. Then replace them one at a time and when the problem returns you’ll know where to look.

I think you’re on to something, thank you very much.