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My alternator was charging 13.6 sometimes 13.8 at idle, but

Customer Question
Hi there, my alternator was...
Hi there, my alternator was charging 13.6 sometimes 13.8 at idle, but when at high rpm always when to 13.2 or lower, I changed the alternator and still doing the same, now don't go higher than 13.4 at idle and 12.9 when driving, batteries are 1month old and I am using the alternator we replaced, 140 amp.
Submitted: 1 year ago.Category: Medium and Heavy Trucks
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Answered in 1 minute by:
11/26/2016
Technician: oldnewenglandmarine,
 replied 1 year ago
oldnewenglandmarine
Category: Medium and Heavy Trucks
Satisfied Customers: 16,419
Verified

Hi Luis, my name is Jason.

Are you measuring the voltage directly at the battery with a hand held volt meter, or are you relying on the gauge in the boats dashboard?

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Technician: oldnewenglandmarine,
 replied 1 year ago

Are you still with me?

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Customer reply replied 1 year ago
Just what it show on the dashboatd
Technician: oldnewenglandmarine,
 replied 1 year ago

Voltage needs to be double checked at the batteries, you could simply have a bad gauge or a bad electrical connection at the gauge. That is the starting point, did you have any further questions for me on the issue?

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Customer reply replied 1 year ago
RI got now it'seems jumping get between 13.3 and 13.5
Technician: oldnewenglandmarine,
 replied 1 year ago

Voltage needs to be double checked at the batteries, you could simply have a bad gauge or a bad electrical connection at the gauge. That is the starting point, did you have any further questions for me on the issue?

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Customer reply replied 1 year ago
Dont have a voltmeter with me
Technician: oldnewenglandmarine,
 replied 1 year ago

Okay. You did pay the website 26 dollars to speak with me, and they did charge you the 26. How is It I can help you?

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Customer reply replied 1 year ago
Will have to go to a Volvo truck shop next week
Customer reply replied 1 year ago
Just want to know why it's charging somewhat good at idle but not at high rpm?
Customer reply replied 1 year ago
The pulley is good fast
Customer reply replied 1 year ago
For the last couple of days don't want to go higher than 13.5-13.6 even at idle, it just to go all the way to 13.8, 13.9.
Customer reply replied 1 year ago
Batteries are new and already change alternator
Technician: oldnewenglandmarine,
 replied 1 year ago

You are in the boat category, is this engine in a boat or some kind of commercial truck? (D13 engines are used in both)

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Customer reply replied 1 year ago
Volvo 780 commercial truck
Technician: oldnewenglandmarine,
 replied 1 year ago

Okay this is the wrong category. I will opt out.

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Customer reply replied 1 year ago
Ok
Technician: Curtis B., Technician replied 1 year ago
Curtis B.
Curtis B., Technician
Category: Medium and Heavy Trucks
Satisfied Customers: 29,462
Experience: Technician turned service manager on multiple lines of trucks and engines, used in industry.
Verified

What is your concern? Are the batteries going dead, or too low to start the truck? The alternator will not charge more than is needed. With new batteries , it is not unusual for alternator to not charge over 13.5 volts. have one on a GMC that will drop down to 10 olts, then when battery gets a little low, I will look over and its charging 15 volts. It always keeps batteries up , and has caused no problems. I batteries go dead, and truck won't start, then it is a problem that needs to be looked at further!

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Technician: Curtis B., Technician replied 1 year ago

I see question is still open, did you see my response?

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Customer reply replied 1 year ago
truck still doing the same, only charging at idle, batteries almost empty.
Technician: Curtis B., Technician replied 1 year ago

I see no indication that voltage drops below 13 volts. Are you measuring voltage at the batteries ? A battery with 13 volts should have plenty of voltage to start the engine. Are batteries lower than 13 volts? What does the battery voltage drop to when trying to crank? You may have too much amperage being drawn by the starter!

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Customer reply replied 1 year ago
Batts are now ok because I let the truck running 70 hours at idle after someone Jumpstart me.
Customer reply replied 1 year ago
At idle charge goes up very slowly, begin jumping from 12.8, 13.1 to 60 hours later 13.9 . 14.1
Customer reply replied 1 year ago
Running it maintains around 13.2, dropping to 12.9 at night with lights on.
Technician: Curtis B., Technician replied 1 year ago

I really don't see that you have a charging problem. But alternator will not charge more than it sees from battery, I would recommend you take it to a good electrical shop and have them check it

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Curtis B.
Curtis B.
Curtis B., Technician
Category: Medium and Heavy Trucks
Satisfied Customers: 29,462
29,462 Satisfied Customers
Experience: Technician turned service manager on multiple lines of trucks and engines, used in industry.

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