[428 tempest]

65 tempest battery light comes on after a couple miles. Replaced alternator and two different new voltage regulators . Also had battery tested they said good. When car is running voltage reads 13.9 - 14 at battery so seems to be charging but light still on ? What's my next step ? Thanks in advance !!

[VCho455]

Is the charge indicator bulb the factory specified bulb?

What alternator are you using?

Can you post a picture of the alternator wiring?

The bulb provide two functions. It gives the driver insight on the charging system operation and it provides resistance to the alternator. GM engineered the system so the light illuminates when the difference between battery voltage and alternator output reaches a certain level. When that voltage difference exceeds that level the light begins to illuminates. The greater the difference the brighter the bulb glows.

It sounds as if the wiring is functioning as it should on start up. I'm going to guess that your problem is heat related. After the few miles of driving and when the light comes on try shutting the car off and restarting it. Does the light continue to stay on or does it go out only to come back on several miles down the road?

The drawing is a basic illustration of the charging circuit.

[428 tempest]

yes light comes right back on after shutting off and restarting . my car is wired like diagrahm also ran a separate ground wire from block to bolt on voltage regulator ? had regulator and alternator retested and both r good. I put a battery tender when it's not driven so I don't know if that's why light doesn't come on until I drive a couple miles ?

[VCho455]

Leave the battery tender off for a couple days and do a test drive to check.

You didn't mention if you have the correct bulb in the system. People sometimes replace them with LED bulbs causing problems.

Here is a link to a page where you can download the factory charging system for 68 Buicks which operate the same as ours do. There is a good description of how the system works as well as troubleshooting help. On page 9 there are explanations for what the charge light is telling you. The main draw back of the factory manual is that is was written so factory technicians could repair vehicles with new wiring harnesses. As a result the manual assumes the wiring is good and that a component has failed. Still its a good resource if you keep that in mind.

https://www.teambuick.com/reference/...files/68-a.php

[428 tempest]

yes original bulbs and wiring

[stellar]

Check fuse holder for corrosion. Measure voltage at #4 terminal of v reg when light is on. measure voltage at both sides of fuse holder.