Alternator Voltage
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Alternator Voltage
I hope some one can help. The voltage meter in my truck starts low at startup 7-9 volts and as I speed up it jumps to 12-14 volts and then stays there. I thought, ok, older truck lots of miles maybe this is normal. This morn. the truck didn't have enough juice to start. Removed the batt's and charged them and the truck starts just fine. Then looked online on how to test the Alternator, no problem seems simple enough, but my volt meter is telling me what appears to be 34volts from both the batt connections and at the back of the alternator. I have an analog volt meter set to read DC on a 50V scale and reading about 32-34 volts?? what am i doing wrong or is the alternator shot?
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Voltage Regulator
Check your voltage regulator on the passenger side fender ( at least thats where they are on 7.3 diesels) the regulator is pretty in-expensive sometimes i have seen where the wires get hot and melt so you may need a new harness connector
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Also i forgot to mention test your alternator with the truck running test from the batt and see what you get then ( should be around 14 ) then turn your lights radio and fan on and check your reading again.
let me know what you get
let me know what you get
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Coolk, I get the same reading from the batt terminal as the cable coming off the back of the alternator, with or without all the electrical gadgets running. I might be reading the multimeter wrong but it seems pretty straight forward. I will check the regulator. thnks
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see the powerstroke is different i think those have the regulator built in the alternator we use a vat-40 to test them but if you dont have test equipment like that you might think about taking it to napa or what ever you have and have them put it on their bench tester and see what they get
Postmaster
Joined: Jan 2003
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From: Durham, NC
First thing, replace your meter!!! If your alternator was putting out that high of a voltage, you wouldn't have a light bulb, or anything electrical still alive!!!! Go to Radio Shack, and buy you a digital meter......
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From: Seattle
Make sure your meter is on DC when you measure voltage. What you described sounds like you could have it set on the 50v AC scale.
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Thanks guys, I am going to buy a new "digital" volt meter and will let you know whats up. My batt was low again this morn. In my original post I had mentioned a low reading from the instrument cluster volt meter (7-9 volts) at startup and while its at this low voltage the alternator is making a grindish noise, but when the meter jumps up to the 12-14 volt range the noise is gone. Is it possible for the bearings in the alternator to slip back into place? an provide normal readings on the handheld multimeter?
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Coolk, yes, there is the one hot bolt on terminal and then a harness. Last night sitting in the drive way at idle the dash meter was in the normal range and I turned everything on (headlights, radio, wipers, ac/fan) and the needle wiggled a little then I tried to lower both front windows and the needle fell almost to nothing. I think I am going to replace the alternator today.