Alternator mystery
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Joined: Aug 2012
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Alternator mystery
For the years that I've owned this truck, it has done this weird thing with the alternator when I start it.
As soon as it fires up the battery voltage gauge is very low, and sometimes the battery light is on with it. After a few minutes and pulsing idle, it'll go to normal range and the idle smooths out with it.
I've cleaned the terminals and posts several times and it tends to help for a short time but always goes back. When tested with a multi meter, the alternator is not cranking out any amperage when the truck starts. As soon as the gauge goes to normal range, the multi meter is reading the appropriate 14.3-14.5 voltage for charging. I've never seen an alternator take so long to start working properly. Is it the voltage regulator, or is this normal? Like I said, it has been like this for years with no issue but I'd hate it to become an issue as I do use this truck all the time for work. This is the only diesel I've ever owned so I'm not sure what's standard or not.
Thanks in advance for any replies.
As soon as it fires up the battery voltage gauge is very low, and sometimes the battery light is on with it. After a few minutes and pulsing idle, it'll go to normal range and the idle smooths out with it.
I've cleaned the terminals and posts several times and it tends to help for a short time but always goes back. When tested with a multi meter, the alternator is not cranking out any amperage when the truck starts. As soon as the gauge goes to normal range, the multi meter is reading the appropriate 14.3-14.5 voltage for charging. I've never seen an alternator take so long to start working properly. Is it the voltage regulator, or is this normal? Like I said, it has been like this for years with no issue but I'd hate it to become an issue as I do use this truck all the time for work. This is the only diesel I've ever owned so I'm not sure what's standard or not.
Thanks in advance for any replies.
Hotshot
Joined: Jan 2012
Posts: 11,132
Likes: 3
From: Southern West Virginia
The gauge is low when it first starts because the glow plugs are pulling a lot of power. When the Wait To Start light goes off, doesn't mean the glow plugs did. When the gauge jumps up to normal is when the glow plugs actually kick off. The battery light being on could be a poor connection on the single wire connector on the alternator. That is the wire for the battery light and sometimes they get damaged from the heater hose laying across them.
Tuned
Joined: Jun 2004
Posts: 472
Likes: 4
From: Goodyear, AZ
Like the other guys said, the glow plugs continue to draw power after the wait to start light goes off and you start the truck. The ECM will allow the alt to start charging once the load is off from the glow plugs
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fordbroncodave
1994.5 - 1997 7.3L Power Stroke Diesel
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May 7, 2013 01:16 PM
