Voltage drop at stops!
 

Was wondering if anyone can help me, my car drops volt at stops and red lights. Have a new battery and alternator. After the new alternator was installed the problem continued but now, my pioneer unit turns on and shuts off. Could it be a radio thing?

Get a volt meter check across battery terminal + and- See what the voltage reads

Get a volt meter check across battery terminal + and- See what the voltage reads . There are 6 cells in batt. 2.2 volts per cell so you should have 13.2 volts when not running give or take. Start car read voltage should be over 14 volts or so. If you don’t have a meter that have battery tester at harbor freight or go to auto parts store should be able to test you’re battery and alt

How low do the volts go? Is the Pioneer thumping or at low volume when the problem occurs? Have you checked the condition of the battery terminals? What effect does turning the headlights on have?

When the car starts it's over 14... as I drive it its a hair over 14 then drops to 12-12.5 at stops.. the pioneer splash screen turns on but then goes black.. doesnt work.. was thinking of pulling the unit out. The headlights have no effect on the car...however if I turn the a/c on, headlights, and all the lights on in the car I do see the volts moving a little at 14. The battery terminals are clean.

Did the voltage issue start before or after the headunit install?

Way after, pulled radio fuse, power socket out and problems continued. Engine off battery volt was at 12.3 and with it on read at 14

What is way after? Weeks? Months? Years? Electrical gremlins are no fun to track down. But I've seen them show up due to an improperly installed electrical component more than 6 weeks after the install. Weird shít happens...

Voltage readings seem normal a bit low (*edited as apparently I'm dyslexic and read 12.3 as 13.2).

12.3 is low Do easy stuff first go to auto parts store they have machine to load test battery, if you have a bad cell in batt It will give you fits. New bat can be bad. If alternator is charging bad batt you just waste time my car has been sitting all week . I have 12.56 volts. 13.2 is normal. Kiss > >>kept it simple. It’s a 12 volt system if batt goes below 12 v. Stuff won’t work right. So I just checked my car running it’s charging at 14.61. Or go back to who put alt in have them check operation

Yea I had amplified in so cal do the install back in 2010. But i ended up pulling and fuses and checking the drop yesterday. Then tried pulling the intake sensor off waiting for check engine light and clearing the code( another person on this forum did that). Then came across a voltage regulator? Never felt with a voltage regulator...anyone mess with that before?

Damn, today my car started then shut down... twice!. The 3rd time I started it and gave it gas before it could shut down... this car is tripping me out!

Just paid $130 for a diagnosis at Fontana Nissan for them to tell me nothing is wrong with the car. Clearly there is.. "it's not throwing a code". I could've told you that. It's normal for volt to drop when there is a load on the car. ... Save your money and dont take it to Nissan!

Just a thought. Does the car have an undersized crank pulley which would not allow the alternator to turn fast enough at idle speeds? Next is to make sure the wiring to the alternator is perfectly clean, tight nut on output terminal and damage free regulator connector. Battery terminals must be clean and tight. Try to twist the battery connections once tightened.
Also North American batteries have smaller diameter posts compared to Japanese batteries which means you may have to install post shims... $5.00 aND 5 minutes work.
Lastly wiggle wires and connections at battery and battery main fuse unit and alternator to see if voltage fluctuates. Can't think of much else without seeing it. Hope that helps.

No, the pulley is stock. The only thing tha has been changed is the alternator and battery. I think the wiring to the alternator is clean since they checked it at Fontana Nissan. I'll try to wiggle wires and see what happens but the connection was tight last time I check.

is it an OEM alternator or one from pepboys etc?

those rebuilt ones from the auto stores can be problematic.

a good alternator should supply enough juice to support all the OEM accessories when the engine is running, you can actually remove the battery and the car would run fine.