Engine/Transmission (1994 - 1998) More Amps

[DSpringstead]

Does anyone have some experiences in installing a larger alternator? I'm considering one & like to know if they will work with the truck's exsisting systems without frying wiring. I'd like one big enough to help offset the intake heaters.

 

[RBeard]

your cables from alt. to battery and have to be able to handle the amperage upgrade,also more amps= more load on engine. I had a direct short on my firetruck (direct drive 300A alt. ) and it almost killed the engine at idle

 

[LVJUNIOR]

I put a mean-green alternator on my truck and it was plug and play. The owner told me the existing wiring is sufficient enough and if I remember right my alternator is 200amps. I have had no problems whatsoever

 

[WilsonF]

The alt can be as big as you want, its the load that requires bigger wiring. So if you only have stock equip. the wiring should be OK.

Floyd

 

[GAmes]

I'd like one big enough to help offset the intake heaters.

If that is the only reason save your money. The stock system has plenty of power for the heaters. On the other hand, if you are adding a large draw component like an inverter then a bigger alternator would make sense.

 

[LVJUNIOR]

If that is the only reason save your money. The stock system has plenty of power for the heaters. On the other hand, if you are adding a large draw component like an inverter then a bigger alternator would make sense.

The stock system does not have plenty of power. My headlights will dim every time the grid heaters kick on with the stock alternator which is one of the main reasons I upgraded. If it is dimming your headlights it is also dropping the voltage to your accessories which in my case some of them are voltage sensitive.

 

[LVJUNIOR]

The alt can be as big as you want, its the load that requires bigger wiring. So if you only have stock equip. the wiring should be OK.



Floyd

I had 6 off-road lights, headlights, a CB radio with 350w amp, VHF radio, GPS, radio, cell phone charger, sattelite radio reciever, on-board air compressor and a 25gph fuel pump off of my transfer tank all running at the same time last weekend and had no problems with the factory wiring

 

[GAmes]

The stock system does not have plenty of power. My headlights will dim every time the grid heaters kick on with the stock alternator which is one of the main reasons I upgraded. If it is dimming your headlights it is also dropping the voltage to your accessories which in my case some of them are voltage sensitive.

Bypassing the PCM to activate the relays manually prior to starting takes hardly any time or skill if a couple iterations of dimming headlights is a big deal. Once the engine is running there is no need for the heater grids anyway. The stock system recharges the batteries from the grid heater load in minutes, therefore, IMO it has plenty of power. You obviously have accessories that require a bigger alternator.

 

[WilsonF]

Good for you

I had 6 off-road lights, headlights, a CB radio with 350w amp, VHF radio, GPS, radio, cell phone charger, sattelite radio reciever, on-board air compressor and a 25gph fuel pump off of my transfer tank all running at the same time last weekend and had no problems with the factory wiring

I guess that proves my point. If you had all that going on, the stock wiring on his truck will be fine.



Floyd

 

[JKosten]

The stock system does not have plenty of power. My headlights will dim every time the grid heaters kick on with the stock alternator which is one of the main reasons I upgraded. If it is dimming your headlights it is also dropping the voltage to your accessories which in my case some of them are voltage sensitive.

First - I live in CA and disconnected my grid heater.



Second - If the grid heater is dimming your lights, check all of your grounds and battery connections. I would also load test your batteries. The factory system is just fine for anything that it came with.

 

[LVJUNIOR]

The grid heater on our motors is a 2 element design. Each element draws 95amps and when both elements are on it draws 190 amps. The starter draws between 350 and 700 amps depending on temperature which will partially discharge the battery and require aditional amperage to bring it back to full charge. For every 12watts of lights (the headlights bulbs are 55 watts each + brake and running lights) you need an additional amp. Our trucks come equiped with 120amp alternators and that is at max output well above idle which leaves. A very large difficite. The batteries will generally cover this difficite long enough for the grid heaters to stop cycling but it is hard on your batteries and if you live in a cold area where your grid heaters get utilizes frequently you should have deep cycle batteries at the very least. Add any aftermarket accessories and you are just plain over driving the whole system.

I have had several people tell me that the factory alternator is sufficient but the math just doesn't add up. If your headlights dim you are dropping voltage and with some of todays aftermarket accessories being very voltage sensitive, not paying attention to the stock alternators inability to provide above 13 volts could cost you your new $800 gps.

 

[fest3er]

Before I start my rant, I must note that the alternator fuse (in the PDC) is 140A. If you install a higher-capacity alternator, you'll likely want to install a fuse with a capacity slightly greater than the new alternator's maximum output.



Now on to my rant.



The stock alternator is a 136A unit. The intake heaters draw about 200A. When they are on, the system voltage will sag from 14. 8VDC down to battery level (13. 5-12. 5VDC). This is still good enough for all accessories.



When the heaters are on, the alternator will be producing its maximum 136A; the remaining current will come from the batteries. The batteries should be rated for around 50AH each; that is, together they can produce 100A for one hour, or 800A for 7 minutes. In fact, they might be capable of producing 6,400A for 40 seconds, or even 24,000A for a few seconds. (Ever see what happens when a stack of UPS batteries, designed to produce 1600A of 48VDC for 20 minutes, is inadvertently shorted through a 750MCM wire? Almost guaranteed to have been not less than 30,000A; the lug at the end mostly vanished. )



With the heaters on, the batteries are supplying 64A (assuming no other loads). Given the heaters are run in about a 50% duty cycle, the average draw on the batteries is closer to 16A each, which is well within their capabilities. And given that the batteries are charged during the off-cycles, the average draw is really closer to zero.



So, if one is using 'starting' batteries, this kind of loading/cycling is exactly what they're designed for: take a little off the top, and put it back. And the heating cycle stops once the vehicle reaches 18MPH or so.



Deep-discharge batteries, on the other hand, are not designed for this type of operation; rather, they're designed to be discharged nearly completely before being recharged. Their lives may be shortened by the repeated discharge/charge cycling.



My '98's heaters are still stock (though I upgraded the relays years ago). I still let them do their thing; I even put it in gear and rev it up to 1100-1200 RPM for a few minutes with my foot on the brake when it's cold (longer when it's frigid). At that RPM, the heaters often turn on and stay on. For a few minutes. The OEM batteries lasted 6-7 years. The Optima RedTops are now at 6-7 years and showing no signs of getting weak.



Other than the shoddy relays Dodge used and the sometimes questionable voltage regulator in the PCM, the intake heating system is well designed and the charging system is well balanced.

 

[LVJUNIOR]

If the voltage was staying at 12. 5-13. 5 you should not see a noticable dimming of your headlights. There is a very good artical written about this on the internet complete with tests specifications and pictures. When one element was on the voltage dropped to 12. 2v when both elements were on the voltage dropped to 11. 75v. And the grid heaters heated to 500°.

Grid Heaters

 

[DSpringstead]

Gentlemen... ...

WOW what a response. I'm picking myself off the floor. To: RBeard, LVJUNIOR, WilsonF, GAmes, JKosten, & fest3er for his constructive "Rant" the information derived from here has been invaluable. Being new my intention is to percieve any future need.

Reason for asking is the stock unit is only going to produce less than 40A at an 800 rpm idle, 136A at 2000 rpm. When the grid heaters come on I see the lights dim, I also hear the engine decrease in RPM, which means the alternator is putting out less and relying more on the batteries to make up the difference. In the NW here we get our share of cold snaps, & with the way people drive, + a 80 mile commute if I get stranded I wanted it to be about bulletproof, not juat enough or OK..... Bulletproof.

fest3er... I forgot all about that pesky 140A ALT fuse in the PDC. Where can one go to find a higher rated one? I had settled on a Meangreen ALT because it produces 100A at a 800 RPM idle. That's over 60A more. How can you go wrong. Trust me gentlemen, I'm open for correction anytime.

 

[GAmes]

Reason for asking is the stock unit is only going to produce less than 40A at an 800 rpm idle, 136A at 2000 rpm. When the grid heaters come on I see the lights dim, I also hear the engine decrease in RPM, which means the alternator is putting out less and relying more on the batteries to make up the difference. In the NW here we get our share of cold snaps, & with the way people drive, + a 80 mile commute if I get stranded I wanted it to be about bulletproof, not juat enough or OK..... Bulletproof.

First, nothing is bulletproof. Second, if the engine is decreasing in RPM, it is the added load on the alternator, but I have never experienced that. Does the tach really drop? The engine doesn't care how many amps are being generated. If you have an 80 mile commute to recharge the batteries what do you care if the alternator only puts out 40A at idle. Grid heaters coming on is temporary at idle and completely stops after 15 mph or so. A couple years ago I was hauling a trailer from Lacey, WA to TX. It was night, cool and raining. My alternator quit somewhere north of Vancouver. I drove to a Portland truck stop and spent the night. The next day I drove to Hermiston, the first Auto Zone in my route, to replace the lifetime warranty alternator. What more could you ask for? Now if you want to spend $$$ to get a higher rated alternator, far be it from me to tell you how to spend your money. Personnally, for the minor annoyance of dimming headlights for a couple minutes, I'll use that money to buy beer.

 

[GSchlegel]

I'll throw in my $. 02.



My '96' has done it sinse day one. The lights dim as the heaters cycle, the interval between diming growing all the time. Even last winter with below zero mornings was not a problem. After waiting about a minute or 2 I then start driving. I take it easy, but by the time I've driven 2 blocks I have accelerated above 18 - 20 mph where the heaters stop cycling. It even appears the voltage drop decreases when I start driving as if 1 of the 2 grids stops being energized. Might be an illusion.

 

[WilsonF]

Many trucks have gone many years with stock Alt. lights dimming and heaters cycling. My 96 has the stock alt. and I live in eastern Wa. can get below 0 never had a problem. But again its your money.

Floyd