In the last couple weeks I have noticed that when I start my truck, the alternator is at about 8 to 10 on the gauge. When I rev it up, the gauge will show at about 12.
I am thinking that the alternator is on its last leg. My question is what size do get. I've seen some posts about 120 amp Alternator? Is this what everyone is using?
glow plugs could still be on, mine reads low untill they turn off on initial startup in the morning then voltage goes up on its own, depends alot on how long the trucks been off though.
an alternator will not put out full amperage until it reaches 1,800 rpm. after it can drop back down and continue full output,they will always produce a little more at a higher rpm though.
My '02 owners manual says the glow plugs can be activated for up to 2 mins after the truck has been started, you'll see a large voltage drop when glow plugs are on, I would not be quick to put an alt. based on your volt gauge. You should have a full charging sys check done before replacing the alt.
Mine will run that same voltage until the glowplugs are turned off. If you leave early in the morning with your headlights on you will see them instantly get MUCH brighter when the GP relay shuts down.
I try to leave the truck running with just the parking lights all the way down the driveway (couple minutes or so) just to give the poor alternator a chance to get some voltage up before I slam it with the headlights and bump the amperage that much more.
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