I removed the noise filter from the alternator power wire and connected it as it was originally.

Starting the car is fine, and the GEN light lights for an oh so brief time. It goes out as usual.

This time, I was watching the volt gauge. I watched as I revved the motor.

When the engine RPMs reach 2000 the volt meter starts dropping from what I assume is upper 14V. The system voltage drops when the engine RPMs reach 2000. Then, at around 2500, the system voltage drops enough or below the battery level, cause the GEN light to come on.

Which blips up past 2500 cause the GEN light to come on even before the gauge reads the drop in system voltage. If the RPMs never get that high the voltage stays up in the 14V area and the GEN light never lights up.

Why, when the the engine RPM rises does the system voltage drop? I am assuming this same thing happened with the previous alternators as the GEN light symptom never changed and the only thing different now it I have an analog gauge I can watch.

I do remember from having the digital gauges that my system voltage was never much above 11V at the gauge and it would in fact change with RPMs. I just wrote it off as a bad after market install and the gauges were the suspect.

Now, with an analog gauge telling me the same thing I am needing to look into other aspects of the charging system.

 

Get your voltmeter out and put it on the 2 wires on the side and see what do in the same test. Also chect the alternator AT the output same test

 

Hmm...me thinks I'll need extra hands for this one.

 

Maybe you need "two" idiot lights.

 

Maybe when I have the two alternators I will.

 

I was going to suggest trying the same test you did at the beginning with one alternator. I am guessing at this point you are still running one.

 

Yes, the two alternators are on my 405, which won't go in for a while. I want to drive the car for the rest of the summer, and I may even put that swap off until next fall.

Right now I still have the hot 350 I built for it a decade ago.

 

My initial guess would be a bad regulator in the alternator.

 

And you think that between a stock 60 amp SI, a 135 amp SI, and a 100 amp CS I would have three bad regulators in a row?

 

Possible, but I wouldn't take those odds to Vegas.

 

 

I think one idiot light should suffice.

 

I'm sorry, which forum is this?

 

Matt hook up the light like we talked about in the other thread and that will narrow it down to the alternator if it still does it.Well no there will be one more poss. variable and that would be the pos lead going from the alt to the starter term.

 

Thanks bud. I will hopefully have the time to do that after work one of these days. I want to get it sorted out by next weekend when I want to start on mounting the hood.

 

D_Boy....
Have you searched for old threads on the alternator topic? I don't know about it, but I remember something about two wires inside the alternator possibly getting switched and ending up with similar symptoms to what you have going. Of course, I have CRS syndrome...but sometimes my memory works. Hope you track it down.

 

My best guess is your not an electrical tech.

 

I did make sure I had everything wired correctly but there is really nothing to screw up. I did not rebuild this CS130, and the plug has lettered leads to corrispond with the two factory wires and the BAT wire.

The only thing I see that isn't 100% common with everyone else's car is I have a ground coming out of my harness that I bolt to the case of the alternator. It was there when I got the car so I have continued to use it.

I wonder if that wire is not a ground at all. I tested it, and it grounded out...but maybe it was just not being used properly.

 

Hey DB. I have seen this happen before. It may,or may not, be the case here. At idle and slow RPM,the charge was fine or marginal. Upper RPM.voltage drop. In this case, the fault was in belt slippage.

 

That wire on my car goes back to the battery ground at the frame