Had to replace my failed OEM alternator that lasted nearly two decades and was short on funds so I got a refurbished Duralast from AutoZone and it ran fine for months but started to make some belt or pulley sound. I intended on trying to inspect the pulleys or adjusting the belt but before I got the chance the dreaded battery light came on and I was fortunately nearby a friends and parked the car in their driveway.

I’ve tested the battery with a multimeter and it shows 12+ volts so it seems good. Haven’t touched the alternator with it because I had to leave somewhere but am assuming that it failed.

Should I just warranty the alternator and put a new one in? Should I replace the OEM belt as well just to make sure?

Not exactly sure what went wrong but man what a headache to have to do it again.

 

I assume you traded in your OEM core when you purchased the Duralast unit? If so, you can try Warranty replacement, but odds are you will be back to replacing it again after some months. The autoparts brand units are terrible and never last. I've never had a unit from Autozone or O'reilly's last longer than the Warranty period. Naturally this will be painful since the process to replace the alternator on 350Zs is very involved.

I wrote a detailed guide on rebuilding the OEM Alternator with quality replacement parts on this Forum. That's the route I recommend if you have the time, patience, and tools requried. But if you want to get a quality replacement that will last AND be budget friendly, I recommend looking for an OE remanufactured unit. Now, who does the re-build and the quality of the parts used will really determine the longevity of the alternator. So you need to select a quality vendor. A new OEM alternator runs over $500, remans range between $150 and $250. Most autoparts units are remanufactured with inferior/cheap bearings and electronics (rectifier/regulator/bearings).

If you don't want to gamble on another aftermarket, or reman unit, then bite the bullet and purchase a brand new OEM alternator.

As for the accessory belt, no need to replace it if it isn't making slipping noises or showing signs of cracking and other damage. I recommend OEM belts over aftermarket, they're cheap. Note: It is possible that if you over-tighten/tension the belts on the VQ35DE (which uses manual tensioners), that you can cause premature failure of the bearings/bushings on the PS Pump, Alternator, idler pulleys, and AC compressor. So be very mindful of this when setting the belt tension on these components.

Good Luck!
-Icer