I changed my starter several months ago, so I know it's good. Last week, my headlights are flickering along with my interior lights. The next day, it died at a red light. I took it to the shop and they changed the alternator. 2 days later, I got a new battery. 5 days (from getting it out of the shop) later and it's not cranking, acting like the battery doesn't have juice. So pretty much a new starter, brand new alternator, and brand new battery.
It sounds like you may have a problem with the battery cables. Check the ends by the battery thoroughly, especially if they have been replaced by universal ones. The main ground cable runs with the starter positive cable and is bolted to the transaxle with the starter bolt. Make sure the bolt is tight.
There is a braided ground wire to check from the transaxle to the body. The nut on the starter and alternator needs to be checked. All of the nuts, bolts, and cables are tight, the starter control circuit needs to be checked, and this can be done with a test light.
If good, the starter positive cable will need to be tested with a voltage drop test. Once the car is running, all the cables will need a voltage drop test. The alternator should be checked for proper voltage and ripple. Ripple is a bad diode in the alternator that causes AC voltage mixed in with DC.
One more thing I've seen is the harmonic balancer (crankshaft pulley) coming apart. You usually can't tell by looking at it. When the pulley for the AC and alternator separates from the rubber, the alternator will not turn at full speed, especially under load. Take the belt off or use a paint marker to see if it is good.
All of that being said, if you replaced the alternator and starter with aftermarket parts, they are not of the same quality as the original. It's possible you may have defective parts. If you would like to have these systems checked for you, a certified technician from YourMechanic can come to your home or office to diagnose your car's starting issue and make any repairs as necessary.
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