Hi Guys,

The alternator on my 66 is giving me some issues. I checked the voltage across the battery terminals when the car was running and the reading I got was the same when the car was not running so I figured the alternator was not charging. I also measured the voltage from the negative battery post straight to the charging lead on the alternator, it only measured the battery voltage. If the battery read 12.2 Volts so would the alternator.

So I took the alternator off and thought I would get it tested before I replaced it, the store that tested it said it was good, so I assumed it must be the voltage regulator.

So I put it back on and I am still only getting the battery voltage reading on the leads from the alternator. It is definitely not charging. The battery slowly goes down and so does the reading from the alternator.

Am I missing something here, if the alternator is good should it not be putting out 13 volts or higher regardless of the voltage regulator if I am measuring the voltage at the alternator.

The belts are tight also and they are not slipping.

Any suggestions before I just replace my alternator? Is it possible that they tested the alternator wrong?

 

Doubtful. I'm not ultra sure how the wiring works, but the voltage regulator may not be energizing the alternator properly. My money's on the voltage regulator. Go to Napa and pick up a quality Echlin unit, I bet everything works fine after that.

 

hiya! do you have an idiot light in the dash? it should go on when ignition is on (so you know the lights working) and it should be off when the car is running (alternator is charging.
In a lot of cars it works in such a way that they put + one side of the lamp (the side away from alternator) and the lamp is then grounded through the alternator (this will cause the lamp to light up). when the engine is running then you'll have 12V on the alternator side as well (plus on both sides of lamp will cause the lamp to be off).

If that bulb is no good then you won't get this effect and the outer coil of the alternator will not be 'energised' -> no magentic field, nothing for the inner coil to use-> no charge.

I cannot say for 100% if your setup uses that exact same system. I was just following Tads thought. So if you have one of those idiot lights and it never comes on chech that bulb. any other case let us know if you have idiot light and when it's on or off

Kalli

 

oh and make sure you have ground on the alternator. that was boogers problem once (engine not grounded)

 

I don't have an idiot light on the dash, I recently replaced all the bulbs in the dash so I am sure there is no idiot light.

I did check the ground just to be sure.

I guess my next step is to replace the voltage regulator.

 

what i meant with idiot light is: either you have a "ALT" lamp in the dash that goes on when you turn on ignition (like the oil lamp). or you have a voltage gauge in the dash. either or.

 

just to answer OPs question a bad ground is the following: lets say you have two lights and you connect both ground wires of them together and put that to the chassis. they should get ground off the chassis. But when the ground is bad (that chassis is not grounded at that point) the current will go from one of the light bulbs to the other (via that cable) and find ground elsewhere. The effect is that multiple lights come on that are in no way related to each other. The most famous example is if you drive behind someone and he steps on the brake and on the left hand side of car (correct) the brakelight comes on and on the right hand side all three lights but half dim.
So when people hear multiple lights on at same time they think ground problem.
This is not the case in your car (i'm quite sure). I am with what mark and Tad are saying you have a batterywire connected directly to the lights or the switch or fuse

kalli

 

I just replaced the voltage regulator, Works Perfect now. I guess I did not quite understand how the charging system works.

Thanks Again,

p.s. Kali, I think your last post was meant for a different thread.

 

yah :-) sorry. that was for the lights stay on man