Alternator output - Chevy and GMC Duramax Diesel Forum
07.5-2010 LMM Duramax Powertrain Discussion of components that are directly involved in the power production and all that is needed to get and keep the truck moving . Engine , Transmission Ect

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Old 12-29-2012, 09:06 AM   eBay Motors  #1 (permalink)
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Alternator output

Something I have noticed especially when it is cold outside. My alternator voltage stays at 12 volts or slightly lower when the truck is started then after as much as 3 or 4 minutes later the voltage will start to climb and settle at 14 to 15 volts. Reving the engine will make no difference. Once the engine is warm and started again this will stop. This is a 2008 truck. Is this normal or something to have looked at?
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Old 12-29-2012, 09:31 AM   eBay Motors  #2 (permalink)
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It's normal. The glow plugs and intake heater suck a lot of power. You see the voltage return to normal when they shut off. Nothing to worry about.
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Old 12-29-2012, 09:51 AM   eBay Motors  #3 (permalink)
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Quote:
Originally Posted by JeffCoD-Max View Post
It's normal. The glow plugs and intake heater suck a lot of power. You see the voltage return to normal when they shut off. Nothing to worry about.
Wow that must be alot of power to bring the alt down that much. Glad to hear that is normal. Thanks, Dean
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Old 12-29-2012, 10:00 AM   eBay Motors  #4 (permalink)
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Not sure if it's the case on the diesels or not, but my Grand Prix used to turn off the alternator when the engine RPM's were below a certain level, usually a normal idle, I believe they did this to take load off the engine at idle
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Old 12-30-2012, 09:30 AM   eBay Motors  #5 (permalink)
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Originally Posted by anthonyshaw View Post
Not sure if it's the case on the diesels or not, but my Grand Prix used to turn off the alternator when the engine RPM's were below a certain level, usually a normal idle, I believe they did this to take load off the engine at idle
Like I stated in the original post, reving the engine did not do anything. I believe the heater statement from the first reply, just surprised that it would that that much power to bring the alt voltage down like that. Dean
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