74 620 charge light stay ON

[sanyantho]

Hi All,

      My truck just started having this problem where the Charge light stay ON. I used the voltage reader to test the battery. It is at 12.8 volt when not running, and does not change much when running. Usually the voltage changed from 12.8 to 14.4 volt when the truck is running. 

     I left the car running and disconnected the positive cable, then my truck died. Which lead me to think that I have a bad alternator. So I brought a new alternator, but still have the same problem. The charge light stays ON, when I am driving. Does anybody know what can be the problem here? I have a 74 620 pick up, weber carb and everything else is stock.

 

Thank you in advance!

Sanyantho

[datzenmike]

Hope you kept the old alternator.

 

Could be the external voltage regulator....

[sanyantho]

Hope you kept the old alternator.

 

Could be the external voltage regulator....

I did not keep the old alternator, turned it in as a core :confused: Do you know how I can test if the external voltage regulator is working correctly?

[TENDRIL]

Generally its more ideal to keep and rebuild the stock alt and starter if possible. Reason being the "new" alt you picked up is 95% most likely a refurbished part  with inferior components compared to the stock ones. unless you dropped the big  $ on a nissan OE alt

 

 

if you got a cheap-O one, you are looking at cashing in on the lifetime warranty several times till you get one that will last you 5 years.

 

Good luck and it sounds like its your voltage regulator  

[sanyantho]

Generally its more ideal to keep and rebuild the stock alt and starter if possible. Reason being the "new" alt you picked up is 95% most likely a refurbished part  with inferior components compared to the stock ones. unless you dropped the big  $ on a nissan OE alt

 

 

Dang! Wish I would have know this. Thanks for the info.

[sanyantho]

So I replaced the voltage regulator, The Charge light gets dimmer but it is still there. When I push on the gas, the Charge light goes away, but it returns when I let go of the gas to idle. Any thoughts?

[TENDRIL]

whats the volt meter say? 

[datzenmike]

So I replaced the voltage regulator, The Charge light gets dimmer but it is still there. When I push on the gas, the Charge light goes away, but it returns when I let go of the gas to idle. Any thoughts?

 

Brushes, maybe one of the diodes is bad. This will reduce output and the least output is at idle. Wait, you replaced the alternator, probably with a lifetime warranty. Take it back and tell them it's not charging. Likely they can't be bothered testing it, and 50% of the time one that tests good is... bad. They'll give you another one. Now you have doubled the chances of getting a good one.

 

Next disconnect your battery and use a known good one. If light is out and charging.... surprise! your battery was bad.

[sanyantho]

whats the volt meter say? 

Volt meter reads about 12.7 and does not increase much when the truck is running. So its not charging like before. Thanks

[sanyantho]

Brushes, maybe one of the diodes is bad. This will reduce output and the least output is at idle. Wait, you replaced the alternator, probably with a lifetime warranty. Take it back and tell them it's not charging. Likely they can't be bothered testing it, and 50% of the time one that tests good is... bad. They'll give you another one. Now you have doubled the chances of getting a good one.

 

Next disconnect your battery and use a known good one. If light is out and charging.... surprise! your battery was bad.

I am going to return it and see. Thanks Mike!

[banzai510(hainz)]

Wish I would have caught this earlier.

 

always have th alt cked out first . Load ck it.

 

 

buy a solid state volt reg. Not a Napa mechanical one made by Elchin or something like that.

 

autozoane and carquest sell a cheape solid state unit

[sanyantho]

So I tried to return the alternator but the store ran a test on it and said it is working good. The clerk  said I should check the wires going to the alternator to make sure it is not bad. So I took the alternator back home, reinstalled, and replace the wht/red wire going to the alternator. Come to find out, the after market alternator does not use the black wire that connects to the alternator and runs to the negative battery terminal. I disconnected the black wire and taped it to the side. Now my truck is charging and the Charge light is off. I checked the battery with a volt meter and it read 13 volt plus. :thumbup:

[datzenmike]

Wa ha ha what ever works.