Strange voltage problem

[badstang123 10+ year member]

I recently put a digital voltage meter in my car so I could keep close tabs on exactly what my voltage was doing. Just to give you a background I have a 200 amp alternator 200 amp alternator, all zero gauge wiring, and two optima red top batteries.

Now here's the weird part. My stereo can draw about 150 amps at full output. To test for any discharge at high output I revved the car up, cranked the stereo, and ran the A/C to see what would happen to the voltage. It stayed right on 14.4 even with all that draw. I was impressed that the alternator was keeping up no problem. Then I realized at night with both A/C and stereo off, when I turned the headlights on the voltage would drop to 13.7 and wouldn't go any higher. I started messing with things and no matter how much crap I had running the voltage would always stay at 14.4 volts. Also if I had nothing running it would stay at 14.4 volts. Then if I turned the headlights on it would always drop to 13.7 volts. Also if I run everything and the headlights it still stays at the 13.7 volts. I wouldn't think 55 watt bulbs draw anymore than 20 amps. That makes me think there has to be something funny going on with something in the headlight wiring. I'm hoping one of you guys has an idea as to what would cause this. I would appreciate any help.

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[Prowler573 5,000+ posts]

I recently put a digital voltage meter in my car so I could keep close tabs on exactly what my voltage was doing. Just to give you a background I have a 200 amp alternator 200 amp alternator, all zero gauge wiring, and two optima red top batteries.
Now here's the weird part. My stereo can draw about 150 amps at full output. To test for any discharge at high output I revved the car up, cranked the stereo, and ran the A/C to see what would happen to the voltage. It stayed right on 14.4 even with all that draw. I was impressed that the alternator was keeping up no problem. Then I realized at night with both A/C and stereo off, when I turned the headlights on the voltage would drop to 13.7 and wouldn't go any higher. I started messing with things and no matter how much crap I had running the voltage would always stay at 14.4 volts. Also if I had nothing running it would stay at 14.4 volts. Then if I turned the headlights on it would always drop to 13.7 volts. Also if I run everything and the headlights it still stays at the 13.7 volts. I wouldn't think 55 watt bulbs draw anymore than 20 amps. That makes me think there has to be something funny going on with something in the headlight wiring. I'm hoping one of you guys has an idea as to what would cause this. I would appreciate any help.

By themselves probably not, friend. But when you have that switch turned far enough that the headlights are on then so are the running (parking) lights, the lights on your license plate, fog/driving lights possibly if you have them, and the lights on your dashboard and climate controls. All that together could easily draw 20 amperes of current.

 

[photocrazy8 10+ year member]

i get the same think, idk why but i have just learned to live with it...cars are weird sometimes...

 

[badstang123 10+ year member]

By themselves probably not, friend. But when you have that switch turned far enough that the headlights are on then so are the running (parking) lights, the lights on your license plate, fog/driving lights possibly if you have them, and the lights on your dashboard and climate controls. All that together could easily draw 20 amperes of current.

I didn't think about that. You are definately right. Even that being the case, there's no way it can draw even half of what my stereo and A/C can.

 

[badstang123 10+ year member]

i get the same think, idk why but i have just learned to live with it...cars are weird sometimes...

At least I'm not alone. It's driving me crazy though //content.invisioncic.com/y282845/emoticons/crazy.gif.c13912c32de98515d3142759a824dae7.gif

 

[photocrazy8 10+ year member]

I didn't think about that. You are definately right. Even that being the case, there's no way it can draw even half of what my stereo and A/C can.

i have the same problem with stock stuff such as turn signals and headlight etc. i think its the way that the way is wired, also check your grounds of where you stock stuff is grounded.

 

[magic_wizard 10+ year member]

When your system is running, make sure all the speakers & subs are actually connected. It's tempting to disconnect them in fear of damaging them at full tilt. When they are connected though, be careful not to damage them, obviously.

 

[badstang123 10+ year member]

I had them connected. It obviously wasn't drawing max amperage all the time. But I have to figure it was probably pulling somewhere between 100-120. Regardless, it's a lot more than headlights and all the stuff that comes on with them can.