Hey guys, I am on the verge of adding new doors to my very base 2001 3.9 atx 2wd. The doors I am getting are full of power & heated mirrors & windows too. I am curious about the alternator. I do not know which unit my base model came with, but I noticed 90, 117 & 136 amp models for my year of Ram on ebay. I know the voltage is controled through the ECU on these & I wonder if I will damage the ECU if I put in a 136 amp unit, or if that is even possible. Has anyone else tried this and have higher amp alternator stories to tell? I know of a kit that makes the voltage regulated externally as the gen 1's were. I just want to know what the options are.

 

Check the main fuse in the PDC. Probably a 140 amp..... You can put as big an alternator on there as you want, and the PCM won't care.

 

I have a 140 amp fuse for sale for that bigger ALT. PM me if your interested.

 

keep in mind the bigger the alternator the more the load it puts on the engine... otherwise they would all be 140amp models..those are for diesels or v8 models with towing package and such.. funny I believe my corvette even with power everything including heated mirrors doesnt even have a 90 amp alternator... I believe 75 or 85 was stock...
unless you plan on running everything at once with a high powere stereo amp and 100watt offroad or fog lights I wouldnt bother and save the gas...

 

That's not really true. They are basically the same size(physically, as in bolt right on). The alternator whether it be a 90 or a 136 only puts out what the load being put on it is calling for. Which in a regular vehicle might be 20 amps? (which is why your vette only needs a 75) The only thing a higher amp alternator does is help the battery recover quicker. Other than that a 136, under normal circumstances puts no more of a load on the motor than a 90. The only time an alternator will put out even close to 136 is if the battery is dead and needs the alternator to recover.

 

hmm seems I was misadvised by the guys over at the vw forum when I upgraded mine from 30 amp to 55...(of course that was a generator to an alternator too)...I knew they were the same size but was told the higher amperage ones put more of a "load" on the engine....
Either way its kind of a pointless upgrade for just power windows and locks and such dont you think?
I did have a car stereo system in my jeep that drew major ampherage (cant remember if it was 70 or 90)...I had to beef up to 0 gauge heavier circuit breaker or it would blow them. it would stall the engine if turned up while idling...It was great on the beach for parties though

 

Apples to oranges, they are right about the generator. It's only 30, so moving to a 55 makes sense(and in those days they were bigger).

As far as radio's, a million lites,plows, speaker amps, etc... A 136 will just keep up quicker. Same load on the engine with a 90, just less time.

And I agree, there is no point of the OP using a 136 just for power doors.

 

The load the engine sees due to the alternator (or generator) is proportional to the electrical load the alternator is driving. Bigger alternators can load down the engine more but only will when the electrical load is larger than the smaller alternator could have supplied.

To bad it weren't true though as it would solve the worlds electrical problems. If bigger alternators electrical loads didn't require more force to turn we'd just put one hamster to drive a billion gigawatt generator and call it a day. Unfortunately in the real world when the electrical load exceeds just a few watts the hamster will no longer be strong enough to turn it.

 

This is all great stuff. I really appreciate the input here. As it stands now, I do not have extra electrical accessories. I installed a cd player with nice speakers, and it dims the lights at half volume or above. Granted, half volume is way louder than stock for sure. I may just get my charging system checked, but I am also curious how to tell which amperage of unit mine is. How can you tell? I can get a used model from any of my local salvage yards for about $35, so upgrading will be easy for me. I am also considering making larger gauge battery cables soon, or at least when it thaws out outside.

 

Download the 2001 factory service manual from the faq's section on this forum.
Under Section 8 click on charging system, then check these specs for altenator ratings at the end of that section.
Also you can call parts dept of local dealer monday and have them print you a build sheet of your truck its free.

Dave