How do you determine when you are at the maximum output level for your alternator.

My recent headlights and auxillary back-up light mod.'s got me to pose this question to myself. IIRC the stock alternator on our trucks are 105amps. The heavy duty option would boost that up to 135amps (of, course there is always the dual alternator option).

When I have my rear 55 watt auxillary back-up lights on at the same time as my headlight mod (high / low beams and fog lights), my alternator gauge only moves up slightly (I'm guessing to about 15 volts - well over 14 is the usual normal position with all lights off, but I never paid much attention to it until adding the mods )

How do you determine what is your max? I know that with A/C house current you pretty much can total all circuit amps in the circuit box by using a couple formula's to determine your max load. Is it the same for our trucks??

Should I be concerned? Auxillary back-up's are not on very much - more concerned about the headlight mods.

Rob

add up the amounts of amps your sucking and if its more than what you can put out you are screwed. Also IIRC all dmaxes get the bigger alt. Also if you temporarily dip into more juice that you are putting out the batteries will cover you. ok.......

I have a snow plow(big big draw), fullsized whirly light bar with strobes and brake light/turnsignal and built in reverse lights(twin 55wers running off a relay in revers), back up alarm, stereo with a seperate amp, com radio, wipers going and the defroster, headlights and all that jive and i havent killed my truck. I also have the 4 high mod done.

add up the amounts of amps your sucking and if its more than what you can put out you are screwed. Also IIRC all dmaxes get the bigger alt. Also if you temporarily dip into more juice that you are putting out the batteries will cover you. ok.......

I have a snow plow(big big draw), fullsized whirly light bar with strobes and brake light/turnsignal and built in reverse lights(twin 55wers running off a relay in revers), back up alarm, stereo with a seperate amp, com radio, wipers going and the defroster, headlights and all that jive and i havent killed my truck. I also have the 4 high mod done.

So what your telling me is "not to worry"
):h

I checked GM's website out of curiosity. The dual alt option gives your 2 - 105's (total of 210amps) but doesn't list what the stock alt is.

Here's how I figured it (these are only guesses):

15 amp - High Beams
15 amp - Low Beams
15 amp - Fogs
15 amp - Aux. Back-up Lt.'s
15 amp - tail lights
15 amp - Interior Lights
15 amp - turn signals
15 amp - brake lights
15 amp - stereo
15 amp - mirrors

150 amps total if they were all being used at the same time to their max circuit rating (I'm sure they are no were close to max)

install a ammeter , inever understood why autos went to voltmeter.

If I remember correctly the formula is:
Watts divided by volts = amp's
Or volt's times amps = watt's

So in your case each 55 watt headlight divided by 13 volts is 4.23 amps
Tailights are lower wattage but I'm not sure what (20 watts maybe)
brake lights 35 watts maybe
Interior lights are small wattage
The big juice sucker is your AC unit

Stock Duramax's have 105 amp alternators
Trucks with snow plow prep packages have the 135 or 145 amp alternator's
And dual setups are 2- 105 amp's

I put a 200 amp powermaster in the second position in mine and have No problem's plowing as far as electrical is concerned.
Start in the morning's and the volt meter jump's right up to 14.5 volt's, it dosen't hang at 10 volt's for 30 seconds like it used to.

Diesel Dragon

If I remember correctly the formula is:
Watts divided by volts = amp's
Or volt's times amps = watt's



I knew this formula was applicable to AC current - didn't know if it applied to DC

Don't forget what the Computer draws!

That's where I know it too, AC current
I would imagine it's the same for DC, but someone correct me if I'm wrong.

theres a formula for everything, i would have to break out my old electronics books . but for a basic dc circuit p(watts)= I(amps)Xe(volts). or any algabraic equivelant,would work. also dont forget ohms law- E divided by IXR, or any algebraic equivalent. have fun get a calculator.

theres a formula for everything, i would have to break out my old electronics books . but for a basic dc circuit p(watts)= I(amps)Xe(volts). or any algabraic equivelant,would work. also dont forget ohms law- E divided by IXR, or any algebraic equivalent. have fun get a calculator.

You forgot E=mc2 ):h

let me see if i remember correctly that formula would give you the potential for a flux capacitor.

Diesel Dragon, you may have a problem. The HD's have a 30 second time delay on start up when you only run on the batteries. This is to protect the onboard computers from power surges or spikes when starting. If your seeing an immediate max value on your voltmeter when you start, for whatever reason, that protection is not there. I'd find out why before you fry something expensive, i.e. ecm, tcm etc.

Yes, I'm saying dont worry;)

I have the plow prep FYI.

I thought all duramaxes regardless of plow prep or not got the bigger alt???

Clamp the cable with a tester and check the draw. Then clamp the wire feeding the battery and check your output.

Clamp the cable with a tester and check the draw. Then clamp the wire feeding the battery and check your output.

I think I know what you mean, but say that again please. Still a little confused.

Well, finally took a look at my alternator. It's a 105 amp. Lower than I thought. Also tested it's output with a volt meter. Pushing about 15 volts under normal load. Thought this was kind of high but confirmed it against the wifes 2001 Yukon which has the same alternator (105 amps) and the Yukon is putting out the same voltage.

This article HERE (http://www.thedieselpage.com/duramax/2005MY.htm) says that the "05's were suppose to have a standard 145 amp. ?????

keepin it
I'm not aware of any time delay in our trucks when they start up.
The only reason the volt meter is slow to move after a cold start is because the alternator has to recharge the batt after there energy has been used to power up the glow plugs.
And maybe I exgarated a little when I said it goes right up to 14 volts.
More like stops at 9 volts for a couple of seconds then decides to keep going to 14 volts. :)