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1976 620 charge light


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Hey guys i recently bought a new battery and an alternator (noticed on another thread that might have been a poor choice). I hooked everything up properly, ive replaced the terminals on every end of the wires because they were broken or worn badly.

I just test drove my truck and the charge light was still on. What is the chance the external voltage regulator has gone bad? Is there a way to test it?

Or does anyone have other suggestions/ questions for more detail?

The charge light was honestly on for quite a while before it ever died if i remember correctly , so i didn't think much of it at first (Durrp).

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A fully charged battery will keep a vehicle running for a very long time. The time is greatly shortened if you start it a lot or use the headlights and heater.


Replacement (cheap rebuilds) are unreliable, so hopefully you kept the old ones and didn't turn them in. What if it's the VR and you put a bad alternator in?


If possible, take the alt in and have a free charge test done on it. If you have the old one, do it also.... for a spare. Have them check that this is the correct alternator for an external voltage regulator. (the '78 and up had a built in regulator)


I guess the last thing is to replace the VR. You can get non mechanical (solid state) external VRs.  

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Alright, thanks for the advice man. Sadly I did not keep the other alternator, but it looked the same as the remanned one.

A couple friends have suggested swapping a chevy style single wire alternator that i believe is internally regulated. Have you heard of that, or have advice?

Also my truck has been getting sputtery at around 2900 - 3200 rpms. (I wont even deny im a complete newbie) and this didnt start until the same time my battery was drained. Not sure what is causing it, for all i know it could be fuel delivery, and poor spark that started it but its apparent now. especially once i get above 45mph. MERRY CHRISTMAS, by the way. Thanks for responding.

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Low battery will not fire the plugs properly.


Yes you can swap in an internally regulated alternator by splicing two pair of wires together, unplugging the auto choke heater and splicing the choke heater to the idle cut solenoid wire. Keep in mind that the 620 does not have a lot of space for a physicaly larger alternator. It's all in the search function, top right of page. Try 620 alternator swap

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If it's not charging the battery, then the battery is low or will be soon. Poor battery voltage may cause poor ignition. Then again it could be the carburetor or valves needing adjustment. If the charge light is on and the battery not charging this is the problem you need to fix first. Worry about all other problems in order.

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Points ignition will run decent down to about 10V.  Electronic needs 12-14V to perform normally..  That could be it. Or you could have low fuel supply.  


I've seen many different alternators installed in Datsuns - from a 1-wire Delco to the Mazda alternator in our race truck.  Just move the upper bracket to make it fit.  

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There must be a good ground connection from the voltage regulator to the body. There must also be a good solid connection between the body and the battery negative terminal. If you look on the negative cable there will be a separate wire to a ground screw near the battery. Make sure the voltage regulator is screwed down tight and well grounded to the sheet metal.


Possibly someone has replaced the battery cable with something generic from NAPA. (which won't have this) You can make a ground wire out of 10 gauge wire and connect from the valve cover bolt to the fire wall.

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