Hi, I've noticed in the last few weeks as the weather has gotten colder my car has a harder time to start. I noticed this more after changing my oil to synthetic but I doubt this is the cause of the problem. I've jumped started my car twice, it seems like the battery holds its charge for about a week then dies. How can I distinguish if the problem lies within a bad battery or bad alternator?
Let me think of all the possibilities:
1. Just double checking, did you use the right viscosity for your oil? 8th Gens run on 5W-20, although 0W-20 works too, especially you live in somewhere cold.
2. Any mods(especially non-OEM ones) involving electrical components? Improperly installed mods can rob battery of its power.
One of my friends installed a massive subwoofer on his VW Golf GTI, and his car battery died twice after installation. Turns out, he installed the switch in a wrong location and it kept draining the battery after the car is off. He fixed that, and no more dead battery.
Check any parasitic power draw with a voltmeter, and also check the surface of the battery. If it's dirty enough, it can also become conductive and become a parasitic power draw (according to EricTheCarGuy).
3. Is it really cold at where you live? If so, check your battery's Cold Cranking Amp
, which shows you the peak current at 0 F(about -17 C). You may want to consider getting a battery with higher Cold Cranking Amp, which makes it easier to start your car in cold weather.
4. How old is your battery? While they last a long while, they do eventually go bad. If it is more than 5 years old, consider getting a new one if it keeps happening.
5. Does the low battery icon flash/light up when you drive your car? That means the alternator is bad.