[Initialpatch]

I should preface by saying that this started after an alternator and battery change. After starting the car, and letting it settle into it's idle (a minute or two) the headlights will pulse dim / bright with the idle. The idle will fluctuate a couple hundred rpm (usually idles at 8-900rpm) up and down. When this happens the headlights "pulse", and so do all lights in the car (dash lights, overheads).

Since then, the car has been to Nissan dealership mechanics twice with the following repairs that could be relevant to this problem.

Mass airflow sensor replaced
Positive battery terminal replaced (was deemed too small by Nissan)

Just got it back a couple of days ago and it is still doing it. The alternator was tested and found to be functioning normally. I am at a loss here. The first piece
of advice I got was that the mass airflow sensor might be going bad. They looked at it, cleared some debris from it, found it to be functioning normally, and finally I had them replace it all together on the second visit.

Any advice would be helpful, thanks in advance.

 

[rogoman]

Pulsing head lights after an alternator replacement seems to indicate a problem with the new alternator. Was the new alternator a reman'd part or an aftermarket part? When replacing electrical components such as alternators, starters and distributors, fuel injectors and sensors, always replace with new or reman'd Nissan OEM components; aftermarket components generally don't last long, don't work right and many times are DOA.

You can try a simple test with a voltmeter. A properly working charging system puts out about 13.2 to 15.0 volts. The voltage reading on your meter should be fairly steady; if you see it jumping around, then the regulator has a problem. A battery should have a static charge of 12.2-12.6 volts when the car is shut off. If a battery is not good, the charging system may not be able to charge properly.

 

[Initialpatch]

Pulsing head lights after an alternator replacement seems to indicate a problem with the new alternator. Was the new alternator a reman'd part or an aftermarket part? When replacing electrical components such as alternators, starters and distributors, fuel injectors and sensors, always replace with new or reman'd Nissan OEM components; aftermarket components generally don't last long, don't work right and many times are DOA.

This is my feeling as well, as the alternator that the first shop put in is aftermarket. The guys at Nissan tested it and said it was fine but in retrospect, they may not have tested it long enough for the symptoms to manifest. It also happens more frequently when the AC/heat is on. Probably because it is drawing power.

 

[Hannahkb2012]

Did you ever resolve your issue with your Nissan? My car, which is also a 2012 Nissan Altima 3.5SR coupe, is going through the same issue after an aftermarket alternator replacement. Would love to hear what you ended up doing to resolve this.

This is my feeling as well, as the alternator that the first shop put in is aftermarket. The guys at Nissan tested it and said it was fine but in retrospect, they may not have tested it long enough for the symptoms to manifest. It also happens more frequently when the AC/heat is on. Probably because it is drawing power.