Back in April, I got a new head unit in my accord. The head unit has the ability to display the system voltage. While driving around I noticed that my voltage would fluctuate from time to time. Most of the time it's around 14v but occasionally it'll drop down to 12.5v. When the voltage dropped to 12.5v the car didn't run any differently and seemed to be fine otherwise. I just assumed the brushes were going in my alternator and were not making good contact. I installed a new alternator yesterday but the problem remains. I didn't think it was normal for the voltage to fluctuate like that while driving. I just assumed it would be 14v no matter what. Any thoughts on this? Perhaps I have some bad grounding? My car is a 95' LX with 166,000 miles. BTW, I verified the voltage readings from my head unit with a multimeter and they are accurate.

 

As far as I know, it's normal. Your car is just using a little extra juice for a second or two........kinda like when you have a really powerful system in your car and the voltage meter fluctuates when the bass hits.

 

mine runs okay and it fluctuates from 8-18 volts...kinda weird.

 

if you want less voltage fluctuation, buy an optima battery, and get a ground kit, and a hyper power kit, which is kinda like a capacitor.
many things cause voltage fluctuation including, headlights, a/c, and stereo.

 

When does it drop to 12.5? Honda's charging system allows the ECU to disable the alternator when it wants to. If the battery is fully charged & the ELD indicates no big power draw, the ECU will short the alternator "C" wire to ground. That tells the alternator to turn off. Then your voltage will go down to 12.5, battery voltage.

Wedley, I don't think 18v would be normal. Something's going on with your voltage regulator??