Alternator question...I hopethis hasn't been answered yet :)
 

Sorry if this is a repost, but does anyone know the idle and peak specs of the 105amp vrs. 145amp??

I need to know if the idle amperage on the 145 is higher than my stock 105??
I get serious voltage drop with this UD pulley when the fans kick in. Plus the sound system doesn't help either :)

Thanks
Nick

I do not know the exact specs but the 145 amp is going to put out more at idle than the 105. I would recommend a 200 amp high output one like I purchased on Ebay. It cost me around $180.00 shipped (1 year ago) and it works awesome. I have stereo equipment and all kinds of extra electrical stuff. I never see the gauge even hit 14 volts at idle with everything running. The guy I purchased it from is Mark Lowe. His Ebay user name is "septowl". I highly recommend him as he stands by what he sells. I had a problem with the original one I purchased and he sent me a new one. I believe he has a starter/alternator business in Jacksonville Florida. This would be the best way for you to go IMO. You will still have room to grow!

The problem is I have a 200amp H.O. now and it doesn't hold up well at idle at all!! It's great when I'm driving, but the output at idle is horrible!! I put the stocker back in and it runs much better. I couldn't even start my truck again when I turned it off when I had the 200amp in :eyes: Kinda sucked actually, but I think it has something to do with the fact that I have a UD pulley so the actual rotation is alot slower!!

That does not make any sense? There is no way a stocker should work better than a 200 amp at idle. Even if you are underdriven. The pulley size should have been the same on both the 105 and the 200. I think you might have a problem with the 200 amp alternator. Even if a larger pulley came with the 200 amp alternator, it should still put out more than the stocker at idle. I would check to make sure there is not a problem with it. You could also check the pully sizes between the 2 alternators. If the 105 is smaller pulley, put it on the 200. That will increase the speed on it and it would improve your idle charge. I still think something is wrong though. My 200 works great!

Something I forgot to mention to you about this before. Did you run a 4 awg cable between the alternator and battery when you had the 200 amp installed? They recommend that you add a 4 awg charging cable along with the factory fusible link wire when using the 200 amp alternator. That might have been why it was not working the way it should. Just another possibility.

High output alts generally sacrifice idle output to achieve higher output at higher RPM. That's why a lot of HO alts will have a tiny pulley on them from the beginning. Most of them won't start making decent power until you get up above 1000-1200 RPM on the engine, and if you put an underdrive pulley on there that number goes up. You will always have bad experiences with a HO alt and underdrive pulley together. What you are experiencing with the 200 amp is perfectly normal. I'm not sure about the output of the 105 vs the 145 at idle, but both should be tons better than your 200 amp.

Did you put an overdrive pulley on the alt when you did the underdrive crank pulley?

Nope I sure didn't!! I put the stocker back on for now and it's working pretty well, but I need more juice for sure!! I'm sitting right at 14 volts in park/nuetral. Then it drops to about 9-11 volts when in drive!! I need to figure something out :( I bought a capacitor for the E fans and that made a huge difference!!! It's alot better when the lights aren't on.

What are your P/N and in gear idle RPMs?

:) 1000

set in EFi in desired idle speed. I only see it when in P/N though...when I go into gear it drops to like 700-800