I just did an up grade to a SB moroso electric pump and taurus electric fan 4500CFM and the new Gm 140 amp altenator. one wire
Problem is at idle , the alt. is not putting out enough power to keep the fan and pump up to speed. lights are real dim at idle. when the RPMS go up, the amp gauge shows charging.. At crusing speed , the needle is almost pinned to the right.. That is not right ... Any solutions for this problem ??
I also ran a 4 gauge wire from the alt to the starter relay pos. post. people say that this is the way to run the wire ..other wise it could melt down the wires to the amp gauge. if i did that I have now amp gauge reading now.. that is normal. after that I got a another alt. pully 1/8" diameter smaller >>> that put the needle in the middle of the amp gauge BUT.......... Lights were still dim and the electical devices were running slow.
What can be done to the alt. to get it to put out more at Idle speed???? I do not want to turn up the idle. Engine runs perfect where it is.
any advice appreciated !!
Thanks in advance !

I had that same problem when I ran the 5" Moroso crank pulley, I went to the bigger March pulley(around 7" I think) and now it charges at idle.

What size pulleys are you running? You are simply going to have to spin it faster at idle to get more output which means a bigger crank pulley, smaller alternator pulley or turn the idle speed up.

the only way to get the alt to put out more at an idle is to increase the speed. A bigger pully on the crank will increase the speed of the alt. Also what regulator are you using?? THe Mopar perf blue on is good and lets it charge at 13.5 volts even at an idle

Is your belt slipping? 140 has allot of drag. I'd check that first,the belt should be firm.

Yes .. forgot to mention ... I installed a aluminum pulley also underdrived. Smaller. Billet.

GM alt. with one aire..
On# # 6 gauge wire from alt to starter relay only... this by passes the alt gauge in the dash so it won't burn the wires up.
No other stock alt. wires are used.. NO Regulator. the alt. is internally regulated.

No .. everything is new .. I did install another smaller pully on the alt. but it may not be small enough in diameter.It appeared to be the same by appearance but was a fraction smaller. It was just a tad bit smaller the the original one. I don't think It made much of a difference.
May have to try another one smaller .

IF I spin the alt pulley faster at idle ,,isn't it going spin faster overall with the engine rpm say .. at 5000 rpm? Or doesn't that matter ? will it hurt anything buy spinning it faster .. maybe overgharge the system // melt the wires ?

I had the exact same problem. Put a heavy ground strap from your head to the frame and everything will be fine

just keep in mind that the alternator speed is normally double crank speed. 5" crank pulley with 2 1/2" alternator pulley at lets say 5000 crank is 10, 000 alternator. Do you spin it higher?

How high is too high on the RPM? for the alt to turn before kabluey

it's probably that power hog of a fan from the taurus causing the problem.
for cars with a heavy electrical demand i just go directly to the 200 amp alternator.
i've burned up so many GM 140's that i have a pile of cores now.

You bypassed the amp gauge with your wiring so you can no longer depend on it to tell you what is going on. Hook up a volt meter and see what the voltage is in a few spots. That should tell you the story.

Running 140 amp GM one wire on mine. 5" crank pulley and underdrive alt. pulley would not charge below 1200rpm when fans, fuel pump on. Went back to stock Alt. pulley 2.5" and it charges fine at idle, even with lights on. Internal regulator will keep it from overcharging. I spin my engine to 6400.

Update >>>>>>>>>> today I got another alt. pulley that is 2.5" in diameter. The Previous pulley was 2.75. Installed the smaller pulley and I seen a little improvement in the charging.
Lights are still dim at idle though but better. ..... I guess I'll have to get a larger diameter crank pulley or turn the idle up some.
or just live with it. oh well !!

I'm pretty sure you didn't build your car to run at idle anyways. Let 'er eat