Alternator Output

[nhrocker]

I'm getting ready to do the 136 amp alternator mod this week. I picked up a used alternator at a local pick'n pull to use. It's a 136 amp one out of a Dodge Dakota, same as a V8 Grand one.

My question is what should the output of the alt be?

I had two different ones tested by Autozone (good thing it's free :laugh3: ) and the guy told me that they were both shot. They only put out 11.5 volts. The guys at the yard I got them from said that it's normal for them to not have full output if you test them when they're out of the vehicle and not in an electrical system. Now I need to find out which guy is telling me BS...

 

[Bender]

If the alternator is internally regulated it will put out enough amperage to keep the vehicle system voltage around 14.5 volts. It will constantly adjust it's output to compensate for varying loads on the electrical system. I'd say your wrecking yard is full of it......or the guy testing the alternator has no idea what he's doing. Considering these new alternator testing machines are designed for all different kinds of makes and models if the machine says it's bad....it's bad.

 

[nhrocker]

Well the yard has a 90 day warranty on alts. That's how I've already gotten 2 from them to test. Should I keep going through them till I find a better one? The other option I have is to try to get some of my money back and take a bad one to Autozone to cover the core charge for a new one. That just means around another $175 to spend...

 

[Bender]

Are you pulling these alts yourself? I'm surprised the yard doesn't have a tester there. I'd grab another and try it out....perhaps have another shop test it for you just to be sure. There is always the chance the machine at the autozone you're going to isn't working properly.

 

[ROBZ95Xj]

That just means around another $175 to spend...

Its a Jeep thing, you SHOULD understand.

 

[nhrocker]

Oh, I understand...I just don't have the money. It doesn't help that I've been without a job for the last month and a half. I bought this last batch of parts with money that was supposed to go towards getting my A/C fixed. I figured upgrading other stuff would be more fun :laugh3:

 

[langer1]

I think the guy a Autozone is trying to sell you a new one, two bad ones in a row is hard to belive.

 

[nhrocker]

I came up with a plan to test wether they're BSing me at Autozone...

One of the guys did mention that they had a new one on the shelf and that I could use the old one as the core charge. Well tomorrow I'm going to have them put the NEW one on the tester and see for myself how they compare...If it's about the same reading, I'll know they we're trying to sell me the new one. If the output is higher, I'll know that I actually did get 2 bad ones with identical output.

Thanks for all the input! I'll let you know how it goes tomorrow!

 

[langer1]

Just watch closely and make sure the settings are the same on the tester, It's not hard ar all to make a good alternator test bad.

Try Advanced Auto their sales people are not on comission.

 

[nhrocker]

I went back to Autozone and had them test both the used alt I brought in and then a brand new one they had. I made sure to watch what the readings were, and come to find out they both read exactly 11.5 volts. After seeing that they ended up checking and finding out that there tester needs work or calibration...

So I've decided I'll just put in the used one I got and hope it really does work. Thanks again!

 

[langer1]

It will work, low output just don't happen often, most of the time they work or they don't work at all.

 

[nhrocker]

Well as it turns out, the tester was off. Since the new one read the same (and they guarantee that it's putting out the full amount of volts...) the used one should also be putting out the full amount, hopefully...

If I get around to putting it in this afternoon I'm going to run it up and have it checked on the in-vehicle tester (which they say works).

While I'm at it, does anyone know any tricks for checking the belt tension? I seem to remember seeing someone doing it with a straight edge and a ruler a while back...

 

[Roll-over]

I went back to Autozone and had them test both the used alt I brought in and then a brand new one they had. I made sure to watch what the readings were, and come to find out they both read exactly 11.5 volts. After seeing that they ended up checking and finding out that there tester needs work or calibration...

So I've decided I'll just put in the used one I got and hope it really does work. Thanks again!

A dollar says the tester never gets "fixed" they pulled a similar fast one with a VW alternator several years back.

 

[nhrocker]

I'm giving them the benefit of the doubt. I try not to come to conclusions about this kind of thing. They've tested the one that I have in there now and told me it was fine, and I was prepared to drop cash for a new one (glad I waited and got a 136 amp one!)

 

[langer1]

I think from what I've seen at Autozone it's more of a case of the Sales people not knowing how to use the equiepment than trying to just make a sale.