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Northern Redneck
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Discussion Starter #1
Anyone know what amp the stock Alt is and can I get a larger one? I notice when my elec fan kicks on, the volts and lights dim. Also,last night I noticed when running the stereo, it was starting to dim the lights real bad without elec fan on. I just had my battery fry, wouldnt hold a charge any more so replaced with an Optima. Now I think my Alt is on its way out,. Stereo is only a 400W amp too. That shouldnt be enoughto cause the voltage fluctuations In was seeing if Alt is good.

Thx in advance

PS what is the basic stock draw, when engine running, lights, stereo and heater Off, anyone know??
 

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'11 5.7L R/T Classic
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4,095 Posts
Anyone know what amp the stock Alt is and can I get a larger one? I notice when my elec fan kicks on, the volts and lights dim. Also,last night I noticed when running the stereo, it was starting to dim the lights real bad without elec fan on. I just had my battery fry, wouldnt hold a charge any more so replaced with an Optima. Now I think my Alt is on its way out,. Stereo is only a 400W amp too. That shouldnt be enoughto cause the voltage fluctuations In was seeing if Alt is good.

Thx in advance

PS what is the basic stock draw, when engine running, lights, stereo and heater Off, anyone know??
I believe the stock alt is 136 amp, and the durango 160 amp is a direct swap.

I don't know this for sure, but I believe the "full accessories" draw of a stock truck is around 80-90 amps. I'd guess without the headlights, stereo, and HVAC it's probably closer to 50-60 amps. E-fans vary greatly in their draw. I've heard of kick on draws of as much as 70 amps, with a 30 amp constant pull.

If you haven't already, I'd recommend the "big 3 upgrade" before you buy a new alternator.
 

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Northern Redneck
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Discussion Starter #3
Big 3 upgrade???
 

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If you have your truck running, a/c or heat on, headlights on, and brake lights applied, you're going to be at about 60 amps for a basic load. Add 30 amps for the e fan, and between 5 to 40 amps for you "little" stereo (400 watts / 12 volts = 33 amps if the amp is 100% efficient, which is impossible, so it could be up to 40ish amps). So your load with the e fan on is 90 amps, with the stereo cranked up, your load is up to 100 amps, with both the e fan and stereo, your load is between 95 to 130 amps.

Also, you have to remember that your alternator output is much less at idle then driving. I would estimate that we are only getting 70 amps or less at idle so you can see it is easy to over load the electrical system.

I would recommend to upgrade the stock alternator with a 160 amp alternator from a durango. If money is tight, you can usually get a used alternator from junkyards for $60 or less. I would also recommend that you watch your load at idle (no blasting the stereo for lengths at a time, etc) unless you like buying batteries and alternators.

Edited to add: I forgot to mention the stock alternator output is 136 amps.
 

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I just noticed you asked what the draw is with your lights and heater off. I would guess about 40 amps. Even with a base load of 40 amps plus 30 amps for the fan, your still at a 70 amp draw.

You can usually get your alternator tested at many parts stores if you think your alternator is shot. I say get it tested sooner then later.
 

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Northern Redneck
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Discussion Starter #6
Ya I have been meaning to upgrade the wires, and I will upgrade the Alt next month. Good to know the Durango is 160.
 

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'11 5.7L R/T Classic
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Ya I have been meaning to upgrade the wires,
Yes, that's the big 3 upgrade. Alternator positive to battery positive. Battery negative to chassis. Engine ground to chassis. You can buy premade 2 gauge cable at most of the big chain auto parts stores so you don't have to do a bunch of splicing and soldering. Get some measurements on each run, then go pick up those 4 lengths of cable (there's a 4th wire on our truck that goes from battery to fuse block). You could skip that run, but might as well just trace the existing stuff and keep it fused.

I've got 1700 watts RMS on tap between my 2 amps and run on the stock alternator. I don't have an e-fan, and I don't crank the tunes that often. I also have HIDs which don't flicker due to voltage drops thanks to the ballast, but I can see my interior lights go from the ~14 volts provided by the alternator to ~12 volts drawing from the battery if I blast the bass. They don't dim out like it's killing the electrical system, but I can see when I've surpassed the alternator and draw directly from the battery's reserve. You can pick up on it on your gauges at night too as they will slightly dim when you hit battery reserve (from 14v to 12v). If you get serious dimming, you're running out of battery reserve, which will kill a standard automotive battery over time. That's why I buy marine batteries that can handle being drained better. :D
 

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I believe the stock alt is 136 amp, and the durango 160 amp is a direct swap.

I don't know this for sure, but I believe the "full accessories" draw of a stock truck is around 80-90 amps. I'd guess without the headlights, stereo, and HVAC it's probably closer to 50-60 amps. E-fans vary greatly in their draw. I've heard of kick on draws of as much as 70 amps, with a 30 amp constant pull.

If you haven't already, I'd recommend the "big 3 upgrade" before you buy a new alternator.
2nd Generation Durango?
 

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what's my bore?
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no the 08 hemi had a 136 amp and a 160 amp stock.
if you had the 4.7 that was the 136 amp stock and you could change to the durango's 4.7 160 amp, but the durango in 08 also had a 136 amp and 160 amp stock. :rolleyes:
 

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Tricked out Ram
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Northern Redneck
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Discussion Starter #12
How to tell what amp Alt you got?
 

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Tricked out Ram
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Or by getting a build sheet for your truck
 

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Average Guy
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My 08 Hemi powered MegaCab came with the towing/trailer package and it has the 136amp alternator in it. I've been thinking of getting the 08 Hemi Durango alt to replace it. I never understood why they put those in the Durango and not the Full Size Trucks.

Also, I think I asked this similar question a year or so back but never got a straight answer about whether the stock 08 Hemi Durango alternator wired up and mounted the same as the 08 Hemi Ram.
 
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