Alternator question

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Yeret

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Hey folks, don't get to post in the first gen forum very often but ever since ma inherited a TBI 318 '91 Dakota, I might be popping in and out a little more often.

Anyway, the Dakota has an overcharging issue with an ECU code that references the voltage regulator. Not knowing the history of the truck and wanting to be safe, we're just gonna replace the entire alternator unit. Now problem one is there are two brand options for the alternator for this year: Bosch and Denso and from what I've been told, they are not interchangeable.

I've already found out that the alternator on this truck is a Denso but I've now found out that there are two options for Denso. One can get either a 90 amp or 120 amp Denso alternator and I cannot determine the output rating of the current alternator. Pops went to Advance Auto earlier today and they claim that the amp ratings are not interchangeable. What I want to know, is this true or is this just think-they-know-it-all parts store guy BS?
 

crazzywolfie

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alternator output should really not make a difference. i put a 120 amp alternator on my 93 that came from the factory with a 90 amp alternator. the only way to see what is on it is if the sticker is still on it. you can see about running the vin and finding out what the stock alternator output was but personally i usually go for the higher output as long as there is really no difference in price.

now i would personally probably test the voltage at the smaller terminals at the alternator. i forget which 1 connects to the asd relay but if it is overcharging there is a possibility that the computer is not accurately seeing what the alternator is putting out. i got a wire hooked to my alternator that i use to jumps the field wire to the alternator output which causes the voltage to drop when it is hooked up. when it is hooked up the voltage output is lower but more consistent especially when put under load like boosting another vehicle.
 

crash68

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I can see there being a difference between the Bosch and Denso alternators. I'm highly doubtful there would be a difference with a higher output version.
Sounds like you need to find a better parts store or possibly a dedicated alternator/starter shop.
 
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