No Charge

Could be just the brush on your Voltage regulator are worn out. Check that first if you can, it's located in the back of the Alt.
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Hey guys,

I'll be the head mechanic on this car for all things reasonable. As Rv5 says there's absolutlely no charge voltage at the battery.

Mike....I'm a little confused....the alternator has brushes....not the voltage regulator....right? And to check them I'd have to pull the whole thing.....which may be in the cards anyway.

I haven't actually seen the alternator yet, but I assume it has two connections....labeled D and B on Mike's pic as I recall. Is B the battery voltage, and D the charge output? Seems I should start right there...checking those voltages?

Thanks for the help now and in the future, we're gonna need you guys!

The journey begins.....Ross

 

Is your alternator light on when you turn the key on, and then, when you start the car and rev the engine?

 

Ross, the brushes are actually on the regulator itself.
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I would put a volt meter on the B terminal at the back of the alt. and start it up. If you have 0 or low voltage then I would pull the alt and rebuild it. Also disconnect the battery and check it for voltage.

 

Mike...thanks for the pic. I see what you're saying...the brushes are the part the alternator but they are mounted on the same piece as the voltage regulator....I guess to make them easy to get to. I've never seen that before....is there something unique about Ferrari alternators and brushes? Do they wear out really quick for some reason?

 

Steve...is the back of the alternator the most conveinent place to make this measurement, or is there another location easier to get to?

Obviously this car is new to us.....and we're just learning our way around the very tight engine compartment.....

 

Not knowing if you have the car on a lift but if you do it is easy to reach the back of the alt. from the bottom of the car. If not then you still can put it on jack stands and get it from underneath. Also if the dash alt light is burned out I think that the alt won't charge. It should light up when you turn on the key. It usually will go out at about 1000 rpm. You might want to check the bulb. To do that just take a piece of dential floss and wrap it around the black G light and pull it out. Then check the bulb and if it is burned out , replace it and see if it works.

 

Hey Steve,

We do have one of those low lifts...I forget the name now...but it'll work fine for that. But we'll definitely check that bulb first....I was wondering if that would shut the system down. And since this one never lights up that sure is suspicious. We'll report back soon.

Thanks, Ross

 

Steve,

Pulled the bulb. Tested its resistance...13.5 ohms....looks good. Tried it on an external 12 volt source...lights up nicely. Checked voltage at the connector.....12 volts. BUT.....no matter what I did I could not make that bulb lite in the connector. I fiddled with it for 15 minutes and never even got a flash. Moved the contacts of the bulb to many different positions...nothing. At one point I bent them out so far I could see them touching the contacts of the connector (I thnk) and nothing?

Could it be a current issue? A bad connection some place else is allowing the voltage to appear but not even enough current to drive a bulb?

Would it be safe to just jumper this temporarily to check the rest of the system while working on this silly light?

Thanks, Ross

 

Ross, Could your problem be with the light socket ground? When you checked the voltage at the socket did you have your meter ground to some part of the car or to the socket?

 

Hey Walt....the socket doesn't appear to be grounded. So when I measured voltage I measured it across the socket terminals, and across the socket connection points, and from the positive side to the vehicle ground. All readings were 12 volts.

Ross

 

From my understanding, the way this light works is that it measures a difference between the voltage at the battery and the voltage coming from the alternator. before startup, there should be no voltage coming from the alternator and 12+ volts coming from the battery, hence the light comes on. After startup you have the same voltage from the alternator and from the battery (minus losses due to resistance differences); then the light goes out. Specifically, you should have 12 or so volts at both leads going into the alternator light.

I am having a similar problem with mine right now. The light never comes on. When I checked the leads going to the light with the engine off, I have 12v at each lead. This makes me think one of the diodes in the voltage regulator is toast, therefore getting 12v on each side of the light BEFORE starting. Also no charging (obviously) while running.

Does this sound right to those that have had similar problems?

 

Do you mean 12 volts on each side with the bulb in or out? Should take this measurement with the bulb out....

 

You could really use my drawing package. The yellow/green wire from the alternator D goes to the charging indicator light and a yellow/black wire from the light goes to the left fuseblock top fuse 1&2. Without that complete connection the alternator will not charge. Probably a broken wire.

Drawing package details at http://www.paul-bennett.com/Images/Wiring.htm

 

Actually, with the bulb out, I am showing a potential diff. of 12v across the leads, but this does not light the bulb. when I ground the connector that goes back to the alternator (yellow/green, I think), the bulb will light. I checked the ground connection that goes to the starter and it appears secure. I am guessing something has failed internally in the voltage regulator...

Right now I am in the process of removing the alternator (fun). I at least found the threads suggesting to remove at the bracket rather than remove the dipstick. (I do plan on turning that bolt around for future removals however...)

Has anyone had any luck getting the alternator out with out removing the coolant return line? I think Atlantaman mentioned something about doing that a few years back before a car show... Not a big deal if I have to remove it. I just need to plan things out for when I can back to work on it (I am out of town for work for the next 10 days...)

 

BlueMax,

You are getting the exact same electrical results we got. !2 volts across the bulb but no light. If you check resistance on the ground side it is very very high though....too high...not enough current to light the bulb. We had our alternator re-built (and upgraded) for $160 and all was fine.

Ross

 

Paul 308 - got one of these for the Mondial?! Man I could really use one..

 

Ross-

Thanks for the info. That confirms my thoughts exactly. I kinda figured that some diodes got fried in the alternator. Looks like I get to finish pulling the alternator when I get back home... I just have to time it right. It's usually poor form when I've been gone for more than a week and the first thing I do is start wrenching on the 308 when I get home. The MRS. doesn't appreciate that a whole lot.... Go figure.

J