Amp draw at idle, help please!

[Ryleighsdad]

Well my car stranded me today. 95 Gt. Turns out the alternator that was less than 6 months old was burnt up, and it killed the battery as well. Replaced both of those, and the new alternator is only putting out 30amps at idle. I read that it should be around 45amps. Also it idles a bit rough. Putting out 13.7 volts.

The car has an aftermarket stereo, and it has an alarm but it is disconnected from power.

What could be causing an amp draw?

 

[Ryleighsdad]

Ok, new symptom. The brand new alternator I just installed today is now fried and not producing power. Immediatly after I installed the new one the volt gauge on the dash would only read on the N, at one point it shot up to the R and stayed for a min or two, then dropped back to the N, and now its barely in the normal range and falling. When I pulled in just now my headlights and gauges were barely working.

 

[ratio411]

The only thing I can really tell you is that after getting some bad alternators right out of the box, now I have the parts store test the new alternator on their bench before I take it home. I had them do it for an alternator I bought just a couple weeks ago, and I apologized for making him do it, but explained I lived 20 miles away and didn't want to have to drive back, and I have had to do it before. He laughed and said he understands, and that they had gotten a whole pallet of new alternators in once that every single one was bad, so he didn't blame me.

 

[Ryleighsdad]

After I installed the alternator (in the parking lot at the store), they tested it and said it was making 13.5 volts and 30 amps. It was tested at the battery terminals. I guess that means that it could have been reading the batteries voltage not what the alternator was making. Damnit, this car is starting to piss me off.

 

[ratio411]

Well, a volt meter at the battery can be done by anyone, and tell you a bit, but the machine in the store tests the actual functions of the internal regulator and such. More than you see at the battery termnals.

 

[Ryleighsdad]

He checked it with the handheld tester. I guess I can take the alt. off and take it to be bench tested tomorrow.

 

[HISSIN50]

It's weird that your alt's output was so low but the voltage was so relatively high. If a load was introduced, did the output fall into the toilet? The alt might have a bad diode.

Good call on the bench test. Pulleys and other ancillaries can affect the idle output, but a big case 3G should put out over 60 amps at idle.

Are you sure none of your wiring was affected during the initial incident?

 

[Ryleighsdad]

You wouldn't believe me if I told ya but here goes.

It was the gauge cluster plug. The side that has the battery light. The excite wire for the alternator runs through the battery light and back to the alternator. if the pin on the plug is not seated correctly the alternator will not get a proper signal and it wont generate. I fixed my pins and it works fine now!

 

[HISSIN50]

The alt should not have functioned at all without the excite signal. Weird. Was the battery-light proving-out?

For info's sake, the signal runs through a resistor in parallel to the bulb. This allows the alt to excite if the bulb burns out.

 

[Ryleighsdad]

Thanks for fixing my miss information. The bulb was not out. The connections where the plug go were all messed up and not making connection.

 

[revhead347]

That sounds familiar. My alternator failed because the printed circuit burned a circuit out. I put another printed circuit in and it burned up in 5 minutes. I thought for sure it was another problem. Turned out I had 2 bad printed circuits in a row.

Kurt