ok guys 3.0 v6 91 toyota pickup has a new high output altenator 90 amp less than a week old, a red top optima batterie new in august and i have replaced my 80 amp altenator fuse under my hood today. my problem is when my rpms are at idle like at a stop lite or just ideling my lights dim and battery guage in my truck droppes to almost 10 volts. everthing goes to normal when i bring my rpms up to 1500 or higher. I dont know if i have a short or something anybody had a similar problem to this. i have been having this problem for a bout 2 months. I Do have a 400 watt stereo system 2 kc lites (driving lites). i have had those accesories for over 3 years and never a problem. any suggestions as to what mite be the problem? THANKYOU VERY MUCH

 

Did you get the alternator model that only charges when you rev it up? I forget what it's called, a one wire or something like that. That or do you have the larger pully model? Those would cause these problems...

 

Well, here is what they did. I suspect they changed the windings in your stator from a "WYE" to a Delta. This makes for good output, but robs from the low end. Now delta wound stators work great, if you have smaller sized stator wires. Other wise, like yours does, it produces little at idle. And in addition to that, did they upgrade the rectifier bridge? (Diodes) if not, they will overheat, melt out and you will lose a phase or two and have little to no output.