For the past week when I'd go to get into my car I'd turn the key over and it would take a good two seconds before the car would start. When it would start, everything starts out dim then lights up and it's fine until the next day. Same thing would happen. Just the other day I had a friend look at it and the positive side on the battery was covered in corrosion. We cleaned off the corrosion, which reset everything in my car and now everything seems to be better. Went to auto zone and told the guy what it was doing before we cleaned it off and he said it's my alternator. Today I get in the car and there are no problems like there was before. Starts up fine and no dimming of lights. Any idea what it could be?
My car has 110000 miles.
My car has an automatic transmission.
Bad connection can be confusing. They are touching and the connection may even be tight, but electricity doesn’t care about what our eyes see. Electricity happens at the atomic level. A bad connection is a loose connection or a surface corrosion. A dirty surface can stop all electric current from flowing.
You stated you cleaned the corrosion off the battery terminal and you had positive results. This is a pretty good sign you are on the right track. My only suggestion is to do this again but buy a battery terminal cleaning tool, some battery cleaner and sealer. Once you see how the tool works, you will have a better idea of what electricity expects for it to do work for you.
Bad connections at the battery or anywhere along the connections from the alternator to the battery will result in a battery that isn’t fully charged. This will act like a bad battery and some will assume the alternator is bad. The fact is, neither of these can be accurately diagnosed without the proper conditions. Once things are as electricity expects, then accurate testing can occur.
I recommend having a certified technician, such as one from YourMechanic, service your battery cables to fix your issue.