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Q: Car won't start and anti-theft alarm goes off when I try to jump it

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Early last night, I was about to get into my car when the key fob didn't work, I didn't think anything of it I just used my key to get in. When I got in I put the key in the ignition and some of the dashboard lights can on very dimly. I turned the key all the way and nothing, it wouldn't even try to start. I instantly thought I must have left a light on or something, and it wouldn't be the first time, the easy solution to that is just jump the battery. We tried to jump the battery with my dad's 2016 Corolla but when we made the connection the anti theft would start going off, and the car would crank but not start. A neighbor came out to see what was going on and he had a battery jumper thing in his car that he used and that got the car started, but the anti theft was still going off. After a minute or so the car died. After that we said we should just try again tomorrow. How can we get this car back in order?

My car has 260000 miles.
My car has an automatic transmission.

A: If the battery is less than 4 years old, ha...

If the battery is less than 4 years old, have it load tested. It will have to be fully charged, though, in order for a load test to be reliable. In your circumstance, if the battery is more than 4 years old, don’t bother testing it; just replace it and buy one with a higher CCA rating than the minimum required for your car (as cars get older, there can be higher resistance in starting circuits, and elsewhere, and so a larger "capacity" battery will be better for you). With the new battery installed you should be fine but it is still recommended that the alternator output be tested (just in case your battery died because of a failing charging system) and in installing the battery be sure there is no corrosion at the connections to the battery. If you want a certified mechanic from YourMechanic install the battery and test the charging system please feel free to schedule those services.

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