hello guys i need your hel with this my truck has stoped working due to a bad alternator i changed it out including the battery the next day it did out on me agin so im guessing my alternator isent working rite i saw that the fuse that comes from the battery to the alternator wich is 175 amp poped so i changed it but still the truck wont charge at all and the alternator passed 3 times in the test in my local part store does any one know wats going on please helpp

 

Check your regular fuses in both fuse boxes, I think there is one for charging (I could be wrong, just a guess). If you popped the mega fuse then the smaller one could be bad also.

Hang in there one of the real electrical guys should chime in soon.

Good luck.

 

Checking all the other fuses is definitely a good idea, but the current that flows from the alternator to charge the battery goes through that 175A megafuse. It's definitely true that with the 175A fuse blown, no charging current will make it from the alternator to the battery, so that would definitely be a reason for the battery running down again after you replaced just the battery and the alternator.

Now that you've changed the alternator, battery, and that megafuse (correct?), what is leading you to believe that the battery still isn't charging? Knowing the answer to that will help further diagnose what's going on.

 

It is a simple matter to check if the alternator is charging.
....Use a voltmeter at the battery and look at the voltage just after starting.
....Since cranking has taken charge out of the battery, it will have to be recharged after the motor starts, as sensed by the regulator.
....What you should see is about 15 volts +, then it should taper down to 14 or less in a few minutes, with a new battery in place.
....I assume your battery charge lamp is on?
.
....Here is how the charge lamp is controlled, telling you either the alternator is charging or not.
....The charge lamp has battery voltage applied to it through the ignition switch as soon as you turn on the switch.
....It gets it's ground from the regulator, to light up when the alternator is 'not' turning at idle speeds or faster.
....As soon as the alternator output comes up, the regulator removes ground from the lamp putting it out, as an indication the alternator is outputting.
....There is not much to the whole circuit besides harness, plugup and fuses..
.....What conditions do you have?
....Is the belt on the pulley? Just making sure!
Good luck.

 

You need a volt meter to test your charging system. Check battery volts while starting and after while it's running. Let us know what those numbers are. The ignition turns on the alternator once the truck is running. If you blew that big of a fuse you may also want to double check your grounds. My guess is the battery shorted and fried the alternator.

 

Im poking at it here, but doesn't the alternator need voltage to it to "tickle" it into putting out any voltage? My thought is that if the alternator does not have that voltage that is where the problem is at. The OP said he had the alternator tested, so I'm assuming that it is good. Also I thought that the 12v. to the alternator was fused.

Or am I just really confused? That wouldn't suprise me!

 

There is a small 20A fuse mounted just under the mega-fuse that supplies the battery feedback voltage to the alternator.

Check it.

 

Called the alternator field fuse? I think ^.

 

i checked evry thing the reson the 175 amp fuse popped was becuse it was loose so it tuched a bit of ground but i just got a new one and fixed that problem ohh and the 20 amp fuse is good i think its the lil pig tail becuse i get power from the batery to the alternator

 

You would have seen right away the charge lead circuit was open if the voltage was tested at the battery and shown not to move after startup.
For the big fuse to be loose, someone has been in there before and never tightened it down.

 

it moves wen i start it up then when i hit the swich to roll down my windos the battery gauge goes down that means it aint charging rite
and yea the guys who instaled my engine broke that pice of

 

If the gage drops (should not move at all or very little) when you run the windows with the motor running, the alternator is not able to put out enough current.
You still have an alternator issue or the charge lead has an issue.
Under these conditions, with very cold temperatures, the battery will be too low on charge and cause slow cranking.

 

well i tried every thing man i feel hoples time to call a mechanic ugh

 

before you do... check all your grounds. In fact. take each one off... clean the area and re-attach. Just a shot, but easy to do and a scratch off the list

 

but if it was the grounds it wouldet even start the truck starts but until the batery uses all its juce the truck just dies out