Voltage question

[MSL]

Ok i have a question i have replaced my alternator and battery they are new and i also put new ends on the cables. My question is when my truck is at a idle the lights are dim and when i give it acceleration the lights get bright. has anyone had this problem and also with this happening could it affect how my truck runs at a idle meaning my coil in my hei isnt getting enough juice at a idle but picks up when accelerating. Also what to do to fix it.?

[BigRed]

My truck has always done that. I think it has something to do with voltage regulation but not sure.

[79BIG10]

I think Scott's right. The alternator kicks in at a certain RPM and then starts charging. I would have the alt. checked out and replace the belt as well.

[PHOENIX]

What is your idle speed in RPM's?
Belts tight and in good shape?
Have alt tested to be safe.
They are right, stock alternators put out very low power at low speeds. They really kick in at 1500-2000 rpms. I have the same problem, but its caused by the electric fan and sterio system.
My lights will slightly dim with every bass line, weather the fan is on or not. The fan turning on dims the lights like a mutha f*cka and I dont like it. I have contacted a few pulley companies. Almost all sell a smaller (overdrive) pulley which will make your alt spin faster at idle, well spin faster all the time.
They rate the overdrive pulleys by a %. Like 5% or 15% overdrive.
They should be able to recommend a safe overdrive for use in a daily driver.
I had part numbers, mfg's, and prices by they are all lost.
I remember I was going to get a plastic pulley, cant remember the exact overdrive, but it was going to cost approx. $35.

Most places will check an alt. for free, try checker, auto zone.
I bought a lifetime alt from checker. Its a 100 amp and was around $80. I have not had one problem with it yet.
I took it to my dads shop (dodge dealer)and we hooked it up to the machine. I was able to see that at idle 700-800rpm the alt output was low. Cant remember the exact numbers. But just off idle, it was pumping out the mad juice 90-100 amps. In my situation I think thats the best. Im drawing more power then stock due to fan and sterio, plus I plan to add more electric sucking devices down the road. Overdrive pullies tend to shorten the life of an alternator, by how much? I have no idea, but Im sure its not by much.

good luck

[MSL]

I dont know what the idles at i need to get a tach to adjust it. and on top of this all my hard drive on my pc is going out so im not sure how long i will be up to talk with you all. if its not onething its another. thanks guys

[LOHRTBT]

I have also been told that a non self exciting alt...ie..2 wire alt is not as bad about it as the one wire self exciting type.

[Mike76251]

I picked this little goodie up off of eBay for a few bucks.
Actually I got this and a matching starter current indicator for $15 or so.
I couldn't find a Snap-On so I had to settle for this 'Blue Point" trade name.
I think Snap-On does that 'cause these "type" things are fragile and easy to break. They don't have to warranty them that way.
Can't really blame them though.

[Mike76251]

Here is how you "hook" it up.
You just hold it up to the wire.

[MSL]

thats cool i didnt even know they made something like that i need one.

[Mike76251]

Originally posted by MSL
thats cool i didnt even know they made something like that i need one.

I didn't know it either until I was 30 yrs. old!!!
Seems they have been around since the late 30's or so.

They work just like a clamp-on amp meter.

[MSL]

Well im only 26 so i guess i just learned something new. i in my whole life helping my dad build trucks and engines and what not have never seen those. I guess he must of done that part of things at the shop he worked at but at home we didnt have those.