Jump to content

voltmeter bounces around, is this normal?

cmoore74

Recommended Posts

cmoore74 Enthusiast

cmoore74

Posted
Posted

Hey all,

 

I just purchased a '06 GMC Sierra crew cab 1500 Z71 back in July. I noticed the voltmeter is not consistent. Sometimes its around 14 V, then I look at it 10 or 15 minutes later and it's just over 15V, 10-15 minutes later it's back down again to 14V.

 

Is this normal? None of my previous vehicles ever had this much variability in the voltage readings. This is the first vehicle I've had with an electric fan so my first thought is it's due to the fan kicking on and off. Then again I've been hearing a lot about bad diodes in the alternators.

 

I guess I should have the dealership take a quick look.

 

Thanks,

Chris

race_man6 Enthusiast

race_man6

Posted
Posted
Hey all,

 

I just purchased a '06 GMC Sierra crew cab 1500 Z71 back in July. I noticed the voltmeter is not consistent. Sometimes its around 14 V, then I look at it 10 or 15 minutes later and it's just over 15V, 10-15 minutes later it's back down again to 14V.

 

Is this normal? None of my previous vehicles ever had this much variability in the voltage readings. This is the first vehicle I've had with an electric fan so my first thought is it's due to the fan kicking on and off. Then again I've been hearing a lot about bad diodes in the alternators.

 

I guess I should have the dealership take a quick look.

 

Thanks,

Chris

 

 

 

 

Chris,

My '05 Silverado CC does the exact same thing. I've never seen another vehicle do it so much, but everything seems to be fine. I see it the most when the air conditioning cycles on and off.

michigan2500hd Senior Enthusiast

michigan2500hd

Posted
Posted

My 05 crew cab does this also. Thought it might be from installing a amp and 2 10" subs but maybe they did change the way the battery is charged.

jhm Senior Enthusiast

jhm

Posted
Posted
Hey all,

 

I just purchased a '06 GMC Sierra crew cab 1500 Z71 back in July. I noticed the voltmeter is not consistent. Sometimes its around 14 V, then I look at it 10 or 15 minutes later and it's just over 15V, 10-15 minutes later it's back down again to 14V.

 

Is this normal? None of my previous vehicles ever had this much variability in the voltage readings. This is the first vehicle I've had with an electric fan so my first thought is it's due to the fan kicking on and off. Then again I've been hearing a lot about bad diodes in the alternators.

 

I guess I should have the dealership take a quick look.

 

Thanks,

Chris

 

 

 

I would have them check it out. My '01 was running high and it turned out to be the diodes. It could cook your battery, making a mess with acid. Brand new truck, why take chances?

ZZebes Senior Enthusiast

ZZebes

Posted
Posted
Any idea why the newer trucks would do this? Is there are benefit over the old system?

 

it wastes fuel to charge the battery when it doesn't need to be

 

 

 

 

 

That doesn't make any sense, the altenator is running all the time, it has no clutch like the AC Compressor, so i dont see how a constant charge wastes fuel...:thumbs:

MS3DALE Senior Enthusiast

MS3DALE

Posted
Posted

Heres a bulletin on it from GM............

 

 

Document ID# 1806618

 

 

 

Subject: Volt Gauge Fluctuation - keywords cluster electrical engine generator intermittent IPC voltage voltmeter wire #PIT3331B - (03/31/2006)

 

 

 

Models: 2005-2007 Cadillac Escalade Models

 

2005-2007 Chevrolet Avalanche, Suburban, Tahoe

 

2005-2006 Chevrolet Silverado

 

2005-2007 GMC Yukon Models

 

2005-2006 GMC Sierra

 

with Regulated Voltage Control (RVC)

 

 

 

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

 

Condition/Concern:

Some customers may comment that their volt gauge is fluctuating between 12 and 14 volts on their full size pickup / utility vehicle.

 

Recommendation/Instructions:

Starting with the 2005 model year, light duty full size pickups and utilities, are equipped with a new Regulated Voltage Control (RVC) system. This system turns off the alternator when it is not required in order to improve fuel economy. The alternator will turn back on when additional voltage is required. This will cause the voltmeter to fluctuate between 12 and 14 volts as opposed to non-regulated systems which usually maintain a more consistent reading of 14 volts. This fluctuation with the RVC system is normal system operation and NO repairs should be attempted.

 

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.

 

 

 

GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.

WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION

 

 

© Copyright General Motors Corporation. All Rights Reserved.

 

 

--------------------------------------------------------------------------------

Document ID# 1806618

asepgrad98 Senior Enthusiast

asepgrad98

Posted
Posted
That doesn't make any sense, the altenator is running all the time, it has no clutch like the AC Compressor, so i dont see how a constant charge wastes fuel..

 

the more amps the alternator puts out the more load gets put on the engine. there is no free energy.

  • 3 weeks later...
mmmikkke Senior Enthusiast

mmmikkke

Posted
Posted
That doesn't make any sense, the altenator is running all the time, it has no clutch like the AC Compressor, so i dont see how a constant charge wastes fuel..

 

the more amps the alternator puts out the more load gets put on the engine. there is no free energy.

 

 

 

 

The alternator doesn't need a clutch because engagement is done electronically. The energization of the rotor windings in the alternator determines how much energy the alternator is drawing off the serpentine belt, and how much energy it's delivering to the electrical system. When less is needed, the regulator lessens the amount of energy being sent to the rotor windings. When more is needed, more energy is sent to the rotor.

 

Details can be found here.

hoorders Enthusiast

hoorders

Posted
Posted
That doesn't make any sense, the altenator is running all the time, it has no clutch like the AC Compressor, so i dont see how a constant charge wastes fuel..

 

the more amps the alternator puts out the more load gets put on the engine. there is no free energy.

 

 

 

 

The alternator doesn't need a clutch because engagement is done electronically. The energization of the rotor windings in the alternator determines how much energy the alternator is drawing off the serpentine belt, and how much energy it's delivering to the electrical system. When less is needed, the regulator lessens the amount of energy being sent to the rotor windings. When more is needed, more energy is sent to the rotor.

 

Details can be found here.

 

 

 

 

 

It sounds to me like just one more thing to go wrong at some point........I bet the fuel savings are so minimal that they can't even be measured.

pm26 Senior Enthusiast

pm26

Posted
Posted
Any idea why the newer trucks would do this? Is there are benefit over the old system?

 

it wastes fuel to charge the battery when it doesn't need to be

 

 

 

 

 

That doesn't make any sense, the altenator is running all the time, it has no clutch like the AC Compressor, so i dont see how a constant charge wastes fuel...:smash:

 

 

 

 

 

What happens is that the alternator is electrically disconnected from the charging circuit when not needed. Even if it is constantly propelled by the belt, it takes less energy to spin it when there is no load on it.

 

The same thing happens if you have a gas powered generator and run it without any load. As soon as you put it under load, it takes a lot more power to drive it and you can hear the engine loading up.

Rolandd Enthusiast

Rolandd

Posted
Posted

You can hear an alternator load the engine when you connect to a dead battery to give some one (or receive) a jump start. I have to wonder how much power would be saved if the headlights went out while driving less than five mph in traffic. I often look at a long line of cars stuck in traffic at night and wonder how much energy is being wasted to light up the bumper of the guy ahead. You figure each car is burning 100 watts for the headlights, that 100 watts must be generated from the car's charging system.

Archived

This topic is now archived and is closed to further replies.

Go to topic listing

  • Latest Articles

  • Posts

    • Zane
      2027 Chevrolet Silverado: Official Discussion

      By Zane · Posted

      It's official. Chevy pulled the covers off the next-gen 2027 Silverado 1500, and we got the first official look.   Full breakdown here: https://www.gm-trucks.com/2027-chevrolet-silverado-official-first-look-specs/   The quick hits: LT is dead. The new core trim is just called "Silverado." Two new V8s, a 5.7L and a 6.6L. No horsepower or torque numbers yet. The 2.7 TurboMax finally gets the 10-speed. ZR2 moves to standard 35s with front and rear lockers. Over 60 inches of dash display on ZR2 and High Country, passenger screen included. Seven trims, three lifted from the factory: ZR2, Trail Boss, and a new Custom Trail Boss.   So let's get into it: 5.7 and 6.6 instead of holding out for a 6.7. Right call? Killing the LT name after all these years: bold, or a mistake? Does the new look land for you, or is it too safe? No power numbers at reveal. Smart tease, or frustrating? What are you ordering on day one?   Drop your first impressions below. 
    • RyanbabZ71
      Gas Prices

      By RyanbabZ71 · Posted

      LOL west coast they need to see what the midwest actually has.  We have been holding at 2.99 for a few weeks now.  Even by work they have come down to 3.02 for the past week.
    • No F-bdy Bs
      Brand new to this forum. Questions about re-gearing my 26’ HD

      By No F-bdy Bs · Posted

      Diesel or gas?  The 37s will obviously, drastically reduce mpg, but the gasser will take a bigger hit to mpg, and power.  Rough guess, but I'd estimate at least a  2mpg hit on the diesel, and up to 4on the gasser. Maybe more.    I wouldn't sweat a gear change on a duramax at all, and unlikely on the gasser either. You're obviously not concerned with acceleration or towing, and the 10spd will find itself in the right gear without much hunting, if any.    If towing, mpg and acceleration are a concern, you're doing the wrong mods.  Either leave it alone, or do the lift/tires and let the chips fall where they may. 
    • Grumpy Bear
      OCI, not when but why?

      By Grumpy Bear · Posted

      I understand. It is disturbing to think a manufacture asks so much and gives so little in engineering support. This is not a GM issues, this is a greed issue and one the ALL practice.    My intent was not to remove the wind from anyone's sail but rather to point out the areas deficient so that they can be discussed with improvements the goal. But to do that you have to know the truth and what that truth is.    The commercial interest are honed in on a few select issues in which they control all the variables and are not forthcoming in the least with their customers about the details. Failure is the only thing that drives these people to improvement. One way not to fail it to manage public "expectations". The set a bar they can clear and put their thumbs under the suspenders with chest puffed.... Only the internal data tells the story fully. As we don't have access to that for decades then we have to generate it ourselves. UOA's with data that matters.  
    • Chuck FB
      OCI, not when but why?

      By Chuck FB · Posted

      I had skimmed through that article when you posted the link and honestly I felt rather defeated in a sense and realized that all these years in changing oil that in fact putting in what I was told was a good quality oil was probably not filtered as well as it should be although the filter put on the engine would be what ( as long as it never went into bypass mode ) would be the final filtering of the new oil that the engine components would first see, but then the filtering media itself is not up to par to what is ideal because a full flow filter would be too restrictive to filter fine enough for the engines best outcome in the long run. Only one of our tractors over the years which was a Versatile with a 855 Cummins had a separate bypass filter, some engine manufacturers did spec a partial bypass system within the main oil filter but I don't believe any other trucks or equipment I was servicing used such a filter. No doubt a product like the Amsoil bypass system is of benefit as long as nothing goes sideways with the extra plumbing and filter such as a rupture/leak that could cause the oil to pump out of the engine ( yes that Versatile had a remote canister with hoses routed to it as well ). With the idiot egr system on a diesel and as a result forcing a lot more soot into the oil, that certainly isn't helping the diesel engines cause or as you pointed out the GDI engine issue with creating more soot and aside from having a fancy secondary filtering system, changing the oil more often helping lower the total soot load.     So oil manufacturing and the end product is not something one can control and I wonder if there are specs on what various oil packaging companies produce in particle count or size. As to the filtering, if the OEM is not designing a filter size and spec that is really what it could be, they too are short changing the end user and so what is the answer. Of course as you say the oil side can only do so much if the air side isn't keeping up its end of the picture and air filters are only so efficient and if in a dusty environment such as farm or construction or driving gravel roads there is a lot of dirt to filter out and some of that ends up into the air stream.    Of course the irony in places like where I am where they dump the salt on the highways but also will mix in some calcium or outright pure calcium for problem road area's, or using calcium as dust control on gravel roads, the vehicle that gets used in that environment may rust out before a properly engineered engine and maintenance finally wears out so one has to face that reality in the rust belt. 

  • GM-Trucks.com Clubs

  • Popular Contributors

×
×
  • Create New...