Hi,

I'm actually a Firebird TA owner, now about to install my 3rd alternator. I've seen many threads about alternators failing and also about pulsing lights... but never yet an explanation of why this is really happening (the pulsing) or is it fixable... until now...

-I found the (factory) info below on a forum dedicated to another car, which continued to use the same alternator after the Firebird ceased. It <appears> to be applicable to our cars as well (I think).

And (if I'm right) adding such a sense wire will improve the performance anyway, since the alternator voltage sensing is better. They were just mean/lazy leaving it out on birds etc...

-So, does anyone else have info on this? Perhaps it's already well known as a fix? (but I didn't notice any posts about it...).

kr

Dermot.
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Condition/Concern:
Customers may have comments of a flickering light condition in the
IPC, interior lamps or headlights. This condition is most likely to be
noticed when the engine RPM is low and when high electrical load requirements are in place on the CS-130D generator.

Recommendation/Instructions:
Vehicles with the listed condition have been found to have a pulse
width charging modulation that ranges alternately from 2% to 97% duty
cycle. This can be observed by checking terminal f with a fluke meter in the
percent range (hertz button pressed twice) and in AC volts.

In order to correct this condition, install a external sense source through the unused "S" terminal at the generator. The generator four-way connector must be replaced with part number 15306009 in order to gain access to the generator sense terminal, which is terminal position d on the connector. The modification involves supplying battery voltage from the battery stud (B+) on the back of the generator using a 0.5-millimeter wire and a ring connector. Next install the appropriate female terminal on the end of the wire and put it into the terminal d position in the new connector (15306009) and install the connector on the generator. This procedure should only be
used for the condition mentioned; other conditions, such as headlights dimming, will not be corrected by the aforementioned procedure.

 

maybe because the stock CS130 is pretty weak to begin with?? ......and you never know what you get with a crappy reman???

 

True about the rebuilt units, but the std alt should be enough for a standard car without much pain, and for sure it shouldn't do odd things like pulse the lights! That was why I was interested in this "fix" and wondered if anyone had actually done it...

-D

 

The flickering light issue is a sign that one of the diodes in the full wave bridge rectifier is dead, and this is part of the voltage regulator.
Alt's produce A/C current, which must be rectified to DC to be of use in a car. A full wave bridge conducts on both sides of zero (think of an A/C sine wave here), or 100% of the charge cycle. When one of the diodes goes away, it still conducts for 50% of the cycle - and you get flickering lights, because the other 50% is dead. You can't see this on the testing machine at the parts store because the meters can't react fast enough to track it, and it'll still show 13v output.

Here's a pic of one:

http://en.wikipedia.org/wiki/Diode_bridge

Bottom line is this...if you have flickering lights, you have a bad alternator.

Tip: anytime you buy an alternator, have the guys at the parts store put it on the machine to prove it's not DOA before you take it home, especially if it's a reman. It still won't find the bad diode, or the diode put in with a bad solder joint, but at least you'll see if it does anything at all or not.

 

Well yes, I know all that, and indeed what a diode bridge is, and 3-phase, and a fair bit more, since I'm an RF/electronics engineer of 30 yrs standing... but this is a specific problem, which I've seen many say happen, often people just change the alt, or fiddle with earths, and it goes away...

But the text in my 1st post is a FACTORY fix for pulsing lights on cars which don't have the alternator sense wire connected and use CS-130D alts - and I think that includes ours. The 'fix' was released after firebirds stopped production.

In any case I will put it on my new (original delco) alt, because remote sense is ALWAYS better than local, IMHO - but I was interested if others knew about this or it has been done by anyone. And it looks like the answer to that is NO in fact.

kr D.