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Fluctuating voltage


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Just installed my new JS alternator 425amp in my truck which was at night and it looked good. I was sitting roughly at 14.6v-15.1v at idle but the next day when it warmed up a bit it was fluctuating like crazy (10.6v-14.9v) and later in the evening when the sun went down and was a lot cooler the voltage was steady like when I initially installed it. My truck has a RVC system and I’m curious if that has anything to do with it, anybody come across this issue? Thanks in advance 

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Steady voltage at night might have something to do with the headlights and taillights. At night, the automatic lights will turn on all the lights needed for night driving. In turn, the voltage controller says "well then we'll need more voltage", and at accordingly. 

Try turning your lights from automatic, to just flat out on during the day, and see what results you get. 

2011 Chevy Silverado under construction

My build log here. Check it out! 

 

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16 hours ago, Dafaseles said:

Steady voltage at night might have something to do with the headlights and taillights. At night, the automatic lights will turn on all the lights needed for night driving. In turn, the voltage controller says "well then we'll need more voltage", and at accordingly. 

Try turning your lights from automatic, to just flat out on during the day, and see what results you get. 

Idk if it was the issue but it’s doing good so far. My truck has a RVC charging system and had one of the stock grounds pass through this sensor. I took that one out a passed through one of the 2/0 grounds I installed with my big 3 upgrade. So far so good. At idle I sit at a solid 14.6v-15.2v

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2 hours ago, mdnjmmy0613 said:

I removed the stock charging wire which was I think a 8awg but I replaced with a 2/0 

That’s why. Install that wire back with that upgraded wire because removing the factory charging wire messes with said vehicle’s voltage.

:stupid:“How can we help you?”
:guido:
“And don’t forget to tell them that 
the customer isn’t always right.”

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3 hours ago, mdnjmmy0613 said:

Idk if it was the issue but it’s doing good so far. My truck has a RVC charging system and had one of the stock grounds pass through this sensor. I took that one out a passed through one of the 2/0 grounds I installed with my big 3 upgrade. So far so good. At idle I sit at a solid 14.6v-15.2v

My truck has one a well. What i've learned is that it's important to not send grounds to the engine block/ alternator without passing through the "ring" first. You can ground to the frame, but the frame grounds should come back up to the negative battery terminal, then through the ring, then to the block. If you pass by the ring, it can cause havoc on the system. What actually happens? I don't know. Just read "don't do it" lol. 

 

2011 Chevy Silverado under construction

My build log here. Check it out! 

 

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1 hour ago, Dafaseles said:

My truck has one a well. What i've learned is that it's important to not send grounds to the engine block/ alternator without passing through the "ring" first. You can ground to the frame, but the frame grounds should come back up to the negative battery terminal, then through the ring, then to the block. If you pass by the ring, it can cause havoc on the system. What actually happens? I don't know. Just read "don't do it" lol. 

 

I just read where he said he uninstalled his vehicle’s factory charging wire and didn’t bother reading the next response lol. I remember what you are talking about and trying to find it on one of Meade’s videos.

:stupid:“How can we help you?”
:guido:
“And don’t forget to tell them that 
the customer isn’t always right.”

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53 minutes ago, 1point21gigawatts said:

I just read where he said he uninstalled his vehicle’s factory charging wire and didn’t bother reading the next response lol. I remember what you are talking about and trying to find it on one of Meade’s videos.

I don't know if I told you, but after all that, I spoke with Tony from mechman. 

For GM trucks, they make a whole bypass setup that also will fool the charging system into thinking the VRC is still in control. No battery light on the dash, and a constant 14.7v from the alternator. I had to order a new alternator though. A 2 pin input instead of a 4 pin. 

With the max charge of the Cyber 12k betting 14.8v, the constant 14.7 will be way safer than the fluctuating voltage from the VRC. 

2011 Chevy Silverado under construction

My build log here. Check it out! 

 

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