2008 G35x no crank no start. So my car has been sitting the past 5 months due to it being my winter beater. Changed the battery and alternator and was out driving running errands with no problems for about 45 minutes. Then I noticed I was losing power with all my warning lights coming on under hard acceleration. I turned the car on and off then that problem didn’t come back. I got home and turned the car off and now it won’t restart. I have no crank. If I hit the push button with out the brake pedal depressed than I can get dash lights to come on but the radio will try to come on and just turn off. When it goes to crank I lose all power except for interior lights. Please help thanks!

 

Sounds like a dead battery, put it on a charger.

You may have a defective alternator, typically you will get the battery light on the dash about an hour before the car actually dies. Test for 14.5vdc with the engine running.

 

car won’t start with jump, battery has 12.4 volts sitting

 

Ok then look for a loose wire or corroded connection. You just installed a new alternator and battery, backtrack your work and look for something that fell off.

If it won't crank with a jump start from another vehicle then something is not connected.

 

Test your battery



Measure the voltage across the battery with your multi meter with both the ignition off and on with your dash lights. A substantial voltage drop is indicative of a weak or dead cell in your battery.
Did you ever measure the alternator voltage after the replacement?
Just because you replaced the battery and the alternator does not mean they are both good.
There is a lot of cheap shyt from China being sold

Good luck