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Alternator & Ignition Light

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roscoe

Jedi Knight
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This goes out to those who have alternators or those who might have an understanding. I switched to negative ground long before I installed my first alternator. I just had to replace it; the first alternator finally lost a diode. I've never had a functional "no charge light" since I made the conversion and to make up for it I put in a small digital voltmeter, which works well. Now, with the new alternator and apparently nothing better to do, I decided to remove the modified regulator I had previously cobbled together to act as a bus bar since I now had an internal regulator. I just spent some extra money on a dummy regulator that has a 50 amp fuseable link ( made by Wosp) and installed the new alternator. Eight years with no warning light was just fine but now I want it to work or die trying.

My issue is this. When I turn on the ignition, I get a nice solid no charge light. When I start the motor, it goes to flickering and never really stays off. Oddly, my cheap little volt meter shows a solid 13.5 to 14.0volts, no jumping around. However, if I measure output at the B+ terminal on the alternator my slightly more expensive dvom flashes voltages between 13.5 and 14.5 flickering very rapidly, sometimes to values slightly more or less than the average 1 volt I see on my dash instrument.

Sometimes the light is off for about half a second, but it always flickers back on, no matter the RPM. My brain hurts from trying to figure this out. The alternator is a Denso, as was used in the '86 and beyond Suzuki Samauri, freshly remanufactured by who ever does that in China and sells them to all the auto parts stores. Nice little unit by the way. It has an S terminal for sensing voltage, which I have not connected, an ignition terminal that turns on the internal regulator, an L terminal which supposedly grounds the no charge light and then supplies voltage when the alternator is spinning, so as to " balance out" both sides of the lamp and cause it to extinguish due to there not being a potential across it. Short of thinking there is a glitch with my new alternator, I'm at a loss. It's probably something obvious but I've already exhausted the internet forums and youtube videos which all make it seem so simple. Any thoughts?
 
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I have a larger 2 wire GM alternator not a Denso and nearly everything electrical makes my brain hurt, but it sounds to me like a fault with the alternator. I can't think of ever having a flickering warning light.

Depending on where you bought it, you might take it to them - I know some auto parts stores can bench test alternators.
 
Is the indicator lamp on the dash an old style filament lamp or an LED ?
 
It's a filament lamp. I may have had the " I've got it moment". I had been doing all of this with the lamp socket removed from the tach housing and dangling under the panel. The light would come on when I turned on the ignition so the ground was there for that and there was obviously power. I figured it all must be correct. Just to tidy up for the night I plugged the lamp holder back into the tach and tried it once more to make sure I hadn't cooked anything in my meanderings. Low and behold, the light went out when the engine started and came back on when shut down. I guess the ground for the lamp comes from the lamp wire on rhe alternator when just the ignition is on, when the alternator comes on line that ground goes away internally and there is voltage on the line. Without the lamp in the tach housing there is no ground for that voltage and perhaps current won't flow to balance out voltage coming from the other wire on the lamp. Does it make sense that a lamp with balanced voltages on both contacts still needs a ground before it will see zero potential across the contacts? I could imagine that answer as either yes or no but never having done that particular experiment I simply do not know and it seems to operate as I hoped it would. At least I won't lie awake tonight thinking about the prince of darkness. I might even hook up the voltage sensing wire tomorrow. It's supposed to be hooked up as close to the battery positive as possible ( again, neg. ground) but I think the hot side of the start solenoid should do.
 
Reid, you are absolutely on the job. I think you changed the title of my post to be specific about the ignition light. If I'm correct, pat yourself on the back for me.
 
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