Intermittent Battery Light
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Freshman User
Joined: May 2013
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From: Northern KY
Intermittent Battery Light
I’ve tried to search for a situation like the one I’m having but nothing has popped up.
I have an 06 f350 with the 6.0L dual alternator set up. About half the time after start up, my battery light will come on for 1-2 min then turn off. This only happens after startup. I e had the batteries and top alternator checked ay a parts store multiple times and each store says they’re good. I’ve also check voltage on both batteries and I come up with 12.54/12.56.
this is my first diesel so I understand the battery drain of the glow plugs and I suspect this is related but I doubt that it should happen. I’m also not familiar with a dual alternator setup and how it may change the way you should test for charging issues.
Thanks for your input.
I have an 06 f350 with the 6.0L dual alternator set up. About half the time after start up, my battery light will come on for 1-2 min then turn off. This only happens after startup. I e had the batteries and top alternator checked ay a parts store multiple times and each store says they’re good. I’ve also check voltage on both batteries and I come up with 12.54/12.56.
this is my first diesel so I understand the battery drain of the glow plugs and I suspect this is related but I doubt that it should happen. I’m also not familiar with a dual alternator setup and how it may change the way you should test for charging issues.
Thanks for your input.
Lead Driver
Joined: Mar 2013
Posts: 7,460
Likes: 85
From: Kent Station, WA
I'd check and clean all of the positive and ground connections.
I'd also recommend moving this thread to the 6.0 section. Maybe @Krewat @Tom or @redford can help.
Further I believe @Too Many Toys has some information on balancing the batteries to look into.
I'd also recommend moving this thread to the 6.0 section. Maybe @Krewat @Tom or @redford can help.
Further I believe @Too Many Toys has some information on balancing the batteries to look into.
Hotshot
Joined: Dec 2014
Posts: 17,827
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From: Jersey Shore
With a dual alternator setup the PCM flips between the two alternators as the first activated alternator, the second alternator coming on after the glow plugs turn off. So one alternator is alway off with glow plugs.
It may be one isn’t working as it should, but the parts stores testing isn’t catching it, not unusual. It may be a bad diode giving an AC ripple but still showing a decent output, so when the glow plugs are on with the poorly functioning alternator, the DC voltage is OK.
A better testing facility should be able to figure it out, or if you have access to a clamp-on ammeter, when the battery light is on check the alternator to see which is turned on and outputting current.
It may be one isn’t working as it should, but the parts stores testing isn’t catching it, not unusual. It may be a bad diode giving an AC ripple but still showing a decent output, so when the glow plugs are on with the poorly functioning alternator, the DC voltage is OK.
A better testing facility should be able to figure it out, or if you have access to a clamp-on ammeter, when the battery light is on check the alternator to see which is turned on and outputting current.
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Freshman User
Joined: May 2013
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From: Northern KY
Thank you! I appreciate you explaining how that works. I’ll make an appointment with my normal mechanic to have him go a bit further. I was most concerned with figuring out if my FICM voltage was falling too low, but when I monitor the system with FORScan everything looks good.
Lead Driver
Joined: Dec 2006
Posts: 6,496
Likes: 94
From: So. Jersey
TooManyToys hit it on how it works.
What I see is you said that only the top alternator was tested, which tested good.
I did not see that you had the lower alternator tested. I would get that lower alternator tested next because that maybe the one that is faulty when the PCM randomly picks it.
What I see is you said that only the top alternator was tested, which tested good.
I did not see that you had the lower alternator tested. I would get that lower alternator tested next because that maybe the one that is faulty when the PCM randomly picks it.
Hotshot
Joined: Dec 2014
Posts: 17,827
Likes: 3,110
From: Jersey Shore
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Fleet Mechanic
Joined: Jun 2006
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I not familiar with the dual setup, so I’m shooting in the dark. If you have a volt meter, you can do this test yourself. I would disconnect one alternator and start the motor. See what happens and check charging voltage. If the red lite stays on and the charging voltage below 13vdc, it is probably the bad alternator. If the alternator checks ok, shut down motor and re- connect alternator. Repeat test on other alternator.
Ed
Ed
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