My alternator light came on yesterday, so I replaced the alternator tonight. This has caused the following results...

Headlights are brighter

Battery seems to be charging

Engine will not turn off when I turn the ignition switch to off

The alternator light is still on

Keep in mind, I  never saw the alternator light come on in the past, so it may be just a loose connection with the light bulb...

Could this be the voltage regulator that is causing me grief? Have any of you had this problem?

I'm going to be selling this truck in the next couple of weeks. If anyone in the southern California area is interested, please let me know. The engine runs very smooth, has newer tires, new alternator lol..., newer master cylinder, newer weber carb, everything else is pretty well banged up though.

Thanks in advance for any advice that you might give.

What year is the 620.  I'm not up on the 620's at all.  You can find the wiring diagrams at .....

http://www.olddatsuns.com/620tech.htm#wd

The '79 doesn't appear to have a volt reg.....I'm wondering if you put in an internally regulated alt in a rig with an external....if that would cause your prob.

It's a 73.... Whether it is needed or not, there is one there...

louinsd wrote: Quote »It's a 73.... Whether it is needed or not, there is one there...[/quote]What is there, a external voltage regulator?   Mike's point is that if your truck has an external regulator, and a 73 does, and you installed an alternator with an internal regulator, that would be the source of your problems.

that was my guess...not sure if it would cause the prob. 

 I have checked the part numbers on the box and of the alt and the sticker on the alt itself. They match up with the part that I bought and the part listed for 77 and below (external regulated) trucks....

How would I tell if the alternator is internally regulated and then mislabled? I'm reading 12.5 volts across the battery when the truck is off, 15.38 when it is running. When I turn on the lights, the alternator increases the load on the engine... This all seems to indicate a happy little electrical system (other than the damn thing won't turn off).

Oh, one other symtom... When I turn the key to the off position, the lights on the dash board dim, like it lost a source of power but not all of it...

Keep in mind the electrical on this truck has always been tempremental. I put a new batery in it 2 years ago and it is now struggling to crank the engine over (it was a cheep battery).

Thanks for the advice!!!

Lou

I'd check the factory manual and see just what the volt reg is supposed to be putting out.....I think the 15+ that you have is on the high side. Should be more like 13-14.  Volts that high will start to overheat your batt and coil.  If you can swap that with another one....that may be your culprit.  There's a chance that you had two things go bad at once.....the new alt is trying to compensate for another problem.


If the alt looks the same as the old one....I doubt it's internally regulated.  Usually, there's a tin cover over the diodes or extra cooling fins cast into the housing.