Need help with 620 charging system.

[Youngblood29]

I let my battery stay in my truck over night and when i come out the next morning to start it its dead. I just replaced the alternator. I dont know what eles to do.

 

[racerx]

U sure alternator is bought one at either autozone or kragens back in the days and brought it back and was bad. Do you have a dvm? Check voltage across when not starting and check when at idle, maybe 1500 rpm. If voltage is like 14.5 or so then charging.

[datzenmike]

Not enough info.

 

 

Why did you replace your alternator?????  What has the truck been doing the last month until now? What have you replaced or changed in that time? If you were sick a doctor would ask questions like this. I think it's called getting a history and it tells them a lot.

[bilzbobaggins]

Before you changed the alternator, did the battery come in the house with you every night?

[datzenmike]

I suspect from your statement you remove the battery every night because the battery is dead every morning. If so this tells me you have a 'draw' on the system when it is not running. Maybe the interior light or the brake lights, stereo amp on were on all night.

 

Buying a new alternator isn't the way to go here. You should trouble shoot and find the problem first then replace the part if needed. In my opinion your original alternator is superior to any re-manufactured junk sold out there. Because you didn't fix the problem you now have added and unknown. What if this alternator is the wrong one? no good? or you failed to install properly? Now you have at least two faults making this 10X harder to solve because a 'new' alternator will automatically be assumed to be good. I hope you kept the old one.

 

Your profile is not complete. You should put the year of your 620 in there. The 620 up till '77 used an external voltage regulator.. it may have failed, be loose and not grounded... Now we have to ask.

[banzai510(hainz)]

about 37 secs onto Scotty Kilmers Battery Drain ved on you tube watch this.

 

 

simple fix

 

 

something is shorting out . alternator could be bad(diaode)

[J's 620]

Why oh why did you replace your factory alt. Chances are they gave you the internally regulated alternator. Big mistake giving up your original. I suggest having the store double check what a 78 620 alternator comes back as. 9 times out of 10 it will be the same thing which is not for your truck. Some simple modification can make that later year alt work. What year is your 620??????

Did you watch the troubleshoot video? Is it fixed?

Find a local alternator shop and see if they can rebuild that p.o.s you bought at auto zone.