Toyota Repair: 1991 landcruiser alternator keeps going out, alternator output, altenators

Question
Maybe this will help , no changes to electical system but a newer Toyota radio/cass/cd, BUT may be you have seen this before and it will help you . when you use the turn signals the volt meter tics up amd down with the indicator flashs. If you can not help , Thanks for trying. John
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Followup To
Question -
I hope you can help about every 6 months the alternator on my cruiser goes out this is number 5 today, it is under warranty at Toyota but I am tired of replacing it. before it goes out the electrical system starts to act up things like the power windows work slowly. The dash gauge is running between half and 18 volts (normal) if you use the windows it will pull the needle down to the middle and if you hold the switch it will drop below the mid part of the range. something is drawing the power or is killing the regulator on all this altenators can you help PLEASEEE ? After a new altenator and same times a battery is put in , it works great for about 6 months sometimes I think it happens between hot and cold weather here in Texas. 80 amp is what toyota gives me it is gas engine.
Thanks, John
Answer -
I can't be of much help with an electrical problem that is this involved, there is obviously something else wrong and you need to ask the dealer to find what that could be, it's not possible for me to diagnose this without actually being able to use test equipment.
Is there any equipment on the vehicle that could draw a lot of current that would exceed the alternator's capcity, something like off-road lights, radio amp etc?
The only other suggestion I have is to go to a 100-120watt alternator.  

Answer
That is an indication of low alternator output or something is drawing way too much current as is the previous stated condition of the windows going up and down slow, I'm kind of lost on this one, have you asked the toyota dealer why this is happening?
Since the warranty on replacement parts is normally 12 months/12,000 miles I'm sure they don't enjoy having to replace the alternator at no charge every six months.