DUAL ALTERNATORS
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FTE Legend
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From: Millersville, MD
DUAL ALTERNATORS
Here is a great question which appears down in the Electrical Forum - think we could answer it here?
"My F-350 diesel has 2 alternators. They seem to be okay now, but sooner or later I will have a problem. So my questions is how does the system work? Is one a backup or do they both work at the same time? If one goes bad do they both get replaced? How would I know which is bad?
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Bob
www.oneminutejesus.com
90 E350, 7.3 IDI Diesel, Auto
99 Expedition 4.6, 4x4
2001 F250 SD 7.3, 4x4, CC, LB, SRW, Auto
2001 F350 SD 7.3, 4x4, CC, LB, DRW, Auto"
"My F-350 diesel has 2 alternators. They seem to be okay now, but sooner or later I will have a problem. So my questions is how does the system work? Is one a backup or do they both work at the same time? If one goes bad do they both get replaced? How would I know which is bad?
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Bob
www.oneminutejesus.com
90 E350, 7.3 IDI Diesel, Auto
99 Expedition 4.6, 4x4
2001 F250 SD 7.3, 4x4, CC, LB, SRW, Auto
2001 F350 SD 7.3, 4x4, CC, LB, DRW, Auto"
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Joined: Aug 2006
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From: Whittier, CA
See bulletin https://www.fleet.ford.com/truckbbas/non-html/Q91.pdf
According to that, the PCM randomly selects one alternator to use when the glow plugs are initiated. If the failed (or removed) alternator happens to be the one selected, the batteries would be discharged.
I've never understood the point in having duals the way Ford chose to implement them. They do not combine output to increase available current.
According to that, the PCM randomly selects one alternator to use when the glow plugs are initiated. If the failed (or removed) alternator happens to be the one selected, the batteries would be discharged.
I've never understood the point in having duals the way Ford chose to implement them. They do not combine output to increase available current.
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From: Millersville, MD
This answer now only adds to my confusion.... so what the he double sticks is the purpose of the dual alternators to begin with? Other than it may save someones job???
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See bulletin https://www.fleet.ford.com/truckbbas/non-html/Q91.pdf
According to that, the PCM randomly selects one alternator to use when the glow plugs are initiated. If the failed (or removed) alternator happens to be the one selected, the batteries would be discharged.
I've never understood the point in having duals the way Ford chose to implement them. They do not combine output to increase available current.
According to that, the PCM randomly selects one alternator to use when the glow plugs are initiated. If the failed (or removed) alternator happens to be the one selected, the batteries would be discharged.
I've never understood the point in having duals the way Ford chose to implement them. They do not combine output to increase available current.
used for auxiliary power for ambulance service, etc. but i don't know
if that is accurate..
it is kinda weird that they think that two 110 amp alternators that
don't work together is better than one 275 amp alternator that
just works.
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i was reading something somewhere about the second alternator being
used for auxiliary power for ambulance service, etc. but i don't know
if that is accurate..
it is kinda weird that they think that two 110 amp alternators that
don't work together is better than one 275 amp alternator that
just works.
used for auxiliary power for ambulance service, etc. but i don't know
if that is accurate..
it is kinda weird that they think that two 110 amp alternators that
don't work together is better than one 275 amp alternator that
just works.
After that, both are running.
I have cited that PDF in argument against the status quo of the operation of a single alternator engine NOT activating the alternator during glow plug operation.
Oh well...
Seems bass-ackwards Ford was so concerned about running on the batteries during glow plug operation and yet go ahead and do that anyways.
Josh
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From: Whittier, CA
All together it doesn't make good sense.
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Drive all day, stop at a drive-thru and shut the engine off (because they complain about the noise in the speaker) and then restart. It can take quite a while to kick the alternator on.
Now THAT doesn't make sense. No need to run glow plugs on a hot engine for 2 minutes.
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That PDF just says that only one alternator is active DURING glow plug activation. It says nothing about only one alternator the rest of the time. Why do we thinK that (a) the alternator isn't running during glow plug activation, since that says one is, (b) the dual alternators don't both run during normal operation, since that PDF doesn't address normal operation, and (c) what do you guys with big alternators do with the two fusible links that the alternator output runs through? Do you replace that cable?
Brian
Brian
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I also have 2 alternators and I don't know how it should work, but I can tell you how mine does work. Read volts w/SGII= at start up 12v for about 20sec then 12.5v for 5 sec then 13v for 5sec then 13.5v for 5sec then 14v. So it takes about a nimute or so to get up to full charging voltage.
Chuck
Chuck
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