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not charging well with new alternator

well i tested the batteries with the cables off and got 12.50 volts on each... which is about 85% charged... so... i dunno. i will test further when i can but am wondering if gage went sour.... also was thinkin about takin the fusable link out and twistin the wires back together see if that works better. so far it has started without jumping etc since friday. :dunno:
 
this is really sucking

just performed some checks witht he volt meter. with truck off batteries read fine. idling read fine. with accessories on voltage dropped. also above idle voltage dropped :( I even went as far as removing the fuseable link from the wire on the back of the alt and crimping it together w/o the link and no change. now i need to put another of them in if i keep this 3 wire alt setup...
 
also just tested the two prong plug on the alt. both side are gettin juice... so thats not it...

even tested battery draw earlier and it seemed normal. :dunno: what gives?

and why would i need a 140 amp alt? i mean is there really that much battery draining from just headlights wipers and blower?

the batteries have 770cca and are brandy new.

:confused:
 
If it won't stay charged, then you have a draw on the battery thats not supposed to be there. lets see if I can explain how to find this :thinking: :thinking:

1.pull all fuses, ALL of them!
2.remove the positive battery terminal from the battery, and hook up your voltmeter inbetween the terminal end and the battery post.
3.start installing fuses one at a time, all the time watching the voltmeter, you should see a momentary surge in some circuts then back to zero, IF, you get a fuse in that pulls a constant voltage, then you've found you problem area.
4. now, if you don't find a draw on the system, now it's time to check the alternator itself for a draw.
5.turn off everything in the vehicle, pull the largest wire off the back of the alternator, install the leads of the voltmeter between that wire end and the attach point for that wire, there should be no power flowing through that circut. if there is the diodes are bad in the alternator, replace alternator.
6.If none of this works then only one thing left. Get a stronger alternator.


Don't be shy about asking a ??? I'm pretty good with this kinda thang! :D
 
thats cool. the multimeter book said to check between the pos cable and the pos terminal 1st for a draw. and the reading seemed as it should so said the book... i spose i should go check all the fuses for a draw. anditappears to be something other than the alternator as i now paid more money for an ac delco after having an issue with the cheapo. since i have to wait till tomorrow after work (dark and cold now) i am wondering if the original alt was say a 100 amp alt and i put in a 78 amp that the computer says is for my diesel burb at the parts store, would that make this big of a difference? i do not know a lot about electrical but it seems weird that i get a voltage drop when the motor is revved up.. :dunno:
 
also another thing i noticed there were a couple relays instead of fuses in the middle of the fuse panel. is this normal?
 
I know this may sound stupid, BUT, is your alt belt good and tight. Reving the motor may ba causing the belt to slip, actually SLOWING the revs the alt is turning.
 
3 on the tree said:
I know this may sound stupid, BUT, is your alt belt good and tight. Reving the motor may ba causing the belt to slip, actually SLOWING the revs the alt is turning.
Click to expand...

brand new belt and it should be tight enough. :waytogo:
 
At the risk of sounding like I don't pay attention, what year is your truck and does it have an external voltage regulator?cuz it sure sounds like a regulator problem. Do what I said in the earlier post and let me know. :D
 
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