Weird behaviour in my Nissan K11?

Question

Hello, I recently got this Nissan, was doing a coolant flush and upon bleeding noticed this behaviour...
When the car starts it runs nice and smooth (for its condition), but if i turn the headlights on, the engine sound changes and the rpm too. If I turn full beams on then the sound changes further. At first I thought it was the battery or alternator, got my multi-meter out the battery seems ok at 12.4V at the terminals. Checked the alternator and this is where it gets interesting. When the car is idling with all electronics off (stereo, lights, door closed) alternator is pumping out 14.5V peak and average 14.4V. When i get my beams on (dimmed) the alternator drops down slightly to 14.2V, but the engine sound changes (sounds as if it isn't getting enough power, as if it is struggling to keep going). When I get my full beams on with radio plugged in the voltage drops to 14.0V. Now the engine sounds very bad. I decided to turn my emergency lights on just to see what will happen, the sound got very bad so wasn't planning on continuing with this test, but before i went to turn the car off, the voltage dropped from 13.9V to 10V for a fraction of a second twice in a row. I turned off, and went to repeat it this time got 13.9V for about 2-3 minutes that i was running without any drop to 10V.
Alternator belt is tight and the pulley has no play and spins freely.
One thing to note, when I step on the accelerator the rpms kick in and the engine sounds ok regardless of the scenario.

I M RIGHT · Answer

I hope it's normal, cuz I've had cars that do the same thing......I'll turn the high beams on, the AC, heater blowers, rear defrost - everything cept the wipers - with engine running to see if my alternator can take it . . . . and with engine off to see if the battery flattens too fast.  Yes, I can get the volts to drop a bit with everything on but have never gone below 11.5.

Now I don't know about the change in sounds:  I have one that "sings" at a different pitch depending on throttle,  but if that's a bad sign - it's been doing it for 6 years.  I think it's just a heavy load on the alternator, perhaps a slightly out-of-alignment belt or such.

Firecracker . · Answer

The only thing weird is the drop to 10V.
The rest is normal.
Idling with no load....
Then add a load to the alternator (turn lights on)....in turn adds a load to the engine. Without adding throttle, it may (usually does) slow the engine a bit.
Turn more lights on (add more load)...ads more load to the engine.

Throttle up, sounds ok.....of course. Engine is making power.

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Weird behaviour in my Nissan K11?

2 Answers