# Weird voltage issue? Expected alternator trouble?



## Livingfortheice (Apr 22, 2014)

Hey everyone. Been a while...

i was was driving up to NH this morning and noticed some weird battery voltage readings...

i currently have an interstate megatron battery that's about a year old.
i have 1 4 gauge power wire from my alternator to my battery
i have 2 4 gauge wires from my battery to my chassis
i have 2 4 gauge wires from my engine to my chassis

i get 14.8 volts when I'm idling and everything is off. With my system pushing 1100 RMS @ 85% I still get 13.6-13.9
todAy, when driving up I was only at 12.5-12.7 volts with no AC and my sound system off with just normal driving. When I would start braking, my voltage would go up to 13.8 within a few seconds and 14.7 within 10 seconds. 
Is this normal, or am I going to be experiencing a alternator failure soon? Any info/education would be greatly appreciated...

thanks,
ben


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## ChevyGuy (Dec 13, 2014)

Unlike older cars, the Cruze will change it's voltage according to need. The 12.5-12.7 may be a little low, but perhaps the battery was fully charged and didn't need to be charged further. The voltage will drop when the engine needs to push the car and rise when braking. It's all part of it's strategy to increase the MPG.


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## obermd (Mar 3, 2012)

Normal.


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## Livingfortheice (Apr 22, 2014)

Phew. I almost crapped myself. I never took the time to notice the driving Voltage. I'm going to do 1/0 gauge wire to replace all that 4 gauge wire, just need to get around to it. Thanks guys!


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## obermd (Mar 3, 2012)

Out of curiosity why all the extra cables going to ground?


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## jblackburn (Apr 14, 2012)

Normal. It will shut off the alternator when accelerating or running down the road with the throttle open, and reengage at optimal times for MPG (decel/coasting) when under a light electrical load


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## NickD (Dec 10, 2011)

Found nothing out of the ordinary with Cruze stock wire gauge sizes, head lamps, battery connections, relay contact voltage drops.

But sure found problems in the very irresponsible means of crimping bare copper wire and dirty relay contacts, and this occurred after the three year warranty ended with not even 30 K miles on it yet. With conductive cables operating under load, head lamps on, blower motor on full, even the rear window defroster, do not expect to read more that 0.1 volts with a simple DVM across any two points. How about over a volt on the ignition relay closed contacts or 2.1 volts between the negative battery cable and the engine block ground.

Dirty point contacts in the relays were found, and corrosion between the crimped terminals and bare copper wires, had to be cleaned and/or soldered.

Since all these vehicles are made the same, if it was my problem, must be your problem as well. Battery terminals come dry from the factory, simple tool for cleaning these and coating with dielectric grease to help retard corrosion.

Very stable 5V logic power supplies can be designed with a very stable output voltage with an input voltage of only 6 volts for a few cents more. Even down to 2 volts for a couple of bucks more by using an up converter, but the bean counters won't let you do this. Found the radio in my Cruze to be the most voltage sensitive, not worth a crap under 11 volts, ECM is only good to about 9 volts using all this cheap crap, and here you having error codes popping up all over the place if your engine will even start. Power on reset is extremely important, won't get this with cheap made in China relay contacts.

So don't wonder why you have problems, is a reason. When my radio started acting up, was time to do some looking.


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## CRAKZOR (May 18, 2016)

add another wire from alternator to bat


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