Charging problem

94 DropTop · Feb 19, 2011

Brand new battery. When im stopped at idle in drive with the headlights on the gauge will shake from 12-14 volts. Any other situation it will just stay at its 14 no problem. This is only while in drive when the idle is around 6-800. If I have the car in park where it is idled up to say 1000-1100 it has no problems. I have had this situation even when my battery was in the front. I alway thought it was the battery but now im starting to think the alt. since it has a brand new battery in it. Im driving the car to work tomorrow to check it out. Any other ideas guys? Since our alts. are 130amps it should put out around 80 on a load test right?

MustangChris · Feb 19, 2011

you got solid grounds?

94 DropTop · Feb 19, 2011

Yes, Like I said this was happening before the battery was ever moved. I have it grounded to the frame in the back and then from the block to the frame twice in the front.

MustangChris · Feb 19, 2011

obviously you forgot to put in a tire-to-frame ground.

when you drive, your tires create static electricity. this static builds up and needs to be grounded to the frame...

anyways, i dont know sh!t about electricity... so i gave it my best guess and will now let someone smarter than me help you.

-Chris

CC'S95GT · Feb 19, 2011

Have the alt ck'd out. It should be putting out bout 14.2-14.8vdc anytime.
You'll get a little fluctuation when you speed up and slow down but the regulator should bring it right back in the 14 vdc range.
Have you verified your idle reading with a scan tool and not off the guage in the car?
If your a couple hundred rpm's off that could cause probs too.

ttocs · Feb 19, 2011

if you are running underdrive pullies, any of them(even if you didn't install the alt pulley) you can expect this to happen, and probably take your alt with them....

94 DropTop · Feb 19, 2011

Actually I forgot about my underdrive crank pulley is still on the car. Thanks ttocs.

ttocs · Feb 19, 2011

there is yer problem. It will lead to a failed alt sooner then later, killed mine and sounds like it might be takin yours............... Did you save your stock pulleys?

blkmcnasty · Feb 20, 2011

94 DropTop said:
Actually I forgot about my underdrive crank pulley is still on the car. Thanks ttocs.

Yea but the Crank underdrive pulley would not affect the alternator. I would check for corrosion on your postive wire connections (at the battery, and alternator) before you go through the hassel of taking the crank pulley off. Also the corrosion may not be obvious like at the bolt or clamp itself, corrosion can happen underneath the insulation of the wire if they are older. Something to think about.

94 DropTop · Feb 20, 2011

All wires are new. It should effect the alt. a smaller crank pulley will not allow the alt pulley to rotate as much as with a bigger pulley.

ttocs · Feb 20, 2011

blkmcnasty said:
94 DropTop said:

Actually I forgot about my underdrive crank pulley is still on the car. Thanks ttocs.

Click to expand...

Yea but the Crank underdrive pulley would not affect the alternator. I would check for corrosion on your postive wire connections (at the battery, and alternator) before you go through the hassel of taking the crank pulley off. Also the corrosion may not be obvious like at the bolt or clamp itself, corrosion can happen underneath the insulation of the wire if they are older. Something to think about.

the crank pulley would not effect the alt? The crank pulley effects everything on the system when its size is changed. It still slows down the alt and everything hooked up to it, not as much as with the alt pulley but it still effects it.

Underdrive pulleys are a quick and easy gain in hp, but there is a cost to it and this is one of them. Now the pulleys cost$50-85, a new alt every few years though will increase the cost...