Voltage dropping when car is hot
Voltage dropping when car is hot Hey guys, I've seen quite a few threads about voltage issues but none really match my symptoms. I have a 2002 z28, no aftermarket sound system or other additional electrical loads other than factory. I noticed after acceleration and I'd left off the throttle my voltage gauge would dip to around 13 and then back up to 13.5-14 range after a second. Before this I noticed all the lights in the car would flicker when in drive at a stop. I replaced the alternator and while it was off, a new belt as well. After this it still did it and I tested my battery, which was bad so that got replaced as well. I also cleaned off all my grounds as precaution These problems have since gone away. Now I'm noticing when that car is first started my voltage gauge in the car reads over 14, close to the tick between 13 and 18 on the gauge. As the car warms up it slowly makes it way down closer to 13. I only work 20 or so minutes away so I dont know if it will get even lower with time but is this normal or should I be looking for something else wrong? I know GM gauges can be a little inaccurate too with age, like all the fuel gauges so that also crossed my mind.
Last edited by rocknroler69; Jun 2, 2018 at 03:51 PM. Reason: Missing information
TECH Fanatic
Joined: Dec 2017
Posts: 1,467
Likes: 265
From: Bossier City, Louisiana
Get a good multimeter and check your DC and AC voltages at the battery with the engine running and rev'd up somewhat. I use a good Fluke 17B multimeter because those cheap / freebie meters from Harbor Freight are notoriously inaccurate, especially for measuring small amounts of alternating current.
Hope for around 14.3 volts DC and less than .02 volts AC . . . a tiny amount of AC. Much more AC than this indicates leaky diodes in your alternator's rectifier circuit.
Rick
Hope for around 14.3 volts DC and less than .02 volts AC . . . a tiny amount of AC. Much more AC than this indicates leaky diodes in your alternator's rectifier circuit.
Rick
I do not think you have a problem. Its normal for the volts to surge upward after starting the car and then return to normal, or about 13.5 V. The alternator and regulator surge the system to compensate for the capacity storage loss used during starting. Only become concerned if voltage drops below 12.5. Below that, the battery slowing discharges and will eventually die.
I do not think you have a problem. Its normal for the volts to surge upward after starting the car and then return to normal, or about 13.5 V. The alternator and regulator surge the system to compensate for the capacity storage loss used during starting. Only become concerned if voltage drops below 12.5. Below that, the battery slowing discharges and will eventually die.
