BCdawg57

iTrader: (1)

Greetings

Some history of my current problem:
I did my LT1 swap around 2008, and since then for besides a few issues here and there the car has ran great. I have the vette serpentine setup, and I used a speartech wiring harness to mate up to the factory body harness. About a year ago I started having intermittent charging problems. I first noticed my voltmeter on my cluster would drop from the 14 volt range to the 11 volt range, it would go back and forth without any noticeable pattern. I figured it wasn't correct because these are known to crap out on these cars. Understand this car does not get driven that much, so any dead battery problems i had I assumed were due to sitting in a garage not being driven, with a 4-5 year old battery. After i let the charging problem dissuade me from driving the car for a while i decided to buy a new battery. Plopped it in and the car drove good for about a week. The voltmeter still read low, but remember i assumed that was faulty. One night a few nights ago a came home after a 25 minute drive, shut the car off for about 5 minutes, tried to fire it back up and click click click. I jumped it pulled it into the garage and busted out my multimeter.

So obviously at this point I assume its an alternator problem, i started with some basic checks after i charged the battery.

Across battery terminals: 12.5v
Battery to b post on alternator 12.5v
Ground on alternator is good
battery while running 12.3-12.7v mostly 12.3 range
alternator while running same as above, even with rpm 1500-2000
I recieve voltage to the 1 red wire on the connector.
Resistance from +battery cable to alternator connector about 460ohms
I went over all of my cables by the battery, checked all my fuses and did not find any problems.
I hooked up free scan just to see what it said and it said it was charging at bout 11.7v

I took the alternator off and took it apart to start checking componets
All the diodes on the rectifier seemed ok, stator has no resistance, brushes still make good contact and the rotor has continuity where it should ect. I did not check the voltage regulator because I do not know how. So according to these tests im not convinced i have an alternator problem. I cleaned all the contacts up and put it back on the car with no change in charging. So I take it back off and take it to autozone and have them test it. It passed 3 times.

I dont know where to go from here, any suggestions?

Thanks

ULTM8Z

What style alternator is this? CS144?

There's no sense wire hooked up to it? I assume the one red wire on the connector is the excitation wire (L wire I think)... Can you get a wire from the S terminal over to the + on the battery to see if that wakes it up? Maybe when they tested it, they had the S terminal hooked up.

BCdawg57

iTrader: (1)

Good idea however I'm not sure how I would do that, the plug literally rests on the valve cover and is hard to access.

​​​​​I did go out and play with it some more and even though all my grounds tested good with an ohm meter I thought maybe the same wasn't the case when the current was higher so I cleaned up this mess of grounds near the fire wall

started the car and it started charging at 13.5-13.7v. I then turned in my high beams and fan motor and it reverted to what it was doing before.

So now I'm thinking grounds, I should probably come up with a better solution than what is in the picture. Just not sure what.

BCdawg57

iTrader: (1)

Just in case anyone has a similar issue ill post my solution. Keep in mind i only know enough about electricity to get me in trouble.

I did what is called a voltage drop test to try and figure out where my bad ground was. This is done by placing your multi meter leads on the 2 ends of whatever you are testing. In the case of a vehicle, a reading of more than 0.2 volts DC is a problem. This is because if there is resistance in the circuit you are testing it will try and bypass that resistance by going through the multi meter, and thus is read as voltage. I placed a lead on negative battery terminal and the other on my alternator casing and was reading 2.xx volts. Since my acc bracket grounds the alternator i probed my negative battery cable because it connects between the block and the acc bracket. What i found is when i put this engine together the bracket was powder coated, and the powder coat was still on the bracket. I filed all this off and my problem was solved! I don't know why is just now started happening, but whatever pathway the ground was taking apparently ceased to be sufficient.