What runs this thing? Is it PCM controlled? I notice that on initial startup the alternator only puts out 70 amps and the batteries are at 11.5 volts, then the exciter wire jumps up then the amperage output will jump to 100 and the voltage jumps to 14 as soon as it does. I don't have a wiring diagram handy at the moment. Has anyone simply put the exciter wire to a switched ignition source?
Alternator Exciter Wire
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dentexpowerstroke
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Which colored wire are you talking about? I have a diagram in the garage I can look at.
On edit: brain fart, I have the diagram for a 6.0. I don't know if they are controlled the same way but if it's the wire I'm thinking you're talking about it gets power from the cluster on a 6.0.
On edit: brain fart, I have the diagram for a 6.0. I don't know if they are controlled the same way but if it's the wire I'm thinking you're talking about it gets power from the cluster on a 6.0.
Same alternator pretty much... It's almost like the alternator isn't put into high gear until the glow plugs are turned off which makes no sense.... why let the batteries suffer while the glow plugs are on?
Strictly Diesel
Active member
PCM controlled. Because of the factory dual alt setups, the PCM chooses between 2 different wires to excite. In single alt trucks, there is a "loopback" in the plug on the passenger side inner fender. That loopback completes the circuit to the single alt if the PCM chooses the second alternator. If you want a second alt, just mount it up and get the harness that goes from the alt to the plug on the inner fender, remove the loopback and plug in the harness...done.
You probably could wire the alt to a key on, but the factory setup seems to work fine.
I believe that the jump from 11.5 to 14 volts is happening when the GPs shut down and are no longer drawing on the electrical system...but I could be wrong. Not sure how the alt would like being asked for full output on cold startup with the GPs at full tilt...it might shorten the life of the alt and it might be easier on the alt the way it's coming online now.
You probably could wire the alt to a key on, but the factory setup seems to work fine.
I believe that the jump from 11.5 to 14 volts is happening when the GPs shut down and are no longer drawing on the electrical system...but I could be wrong. Not sure how the alt would like being asked for full output on cold startup with the GPs at full tilt...it might shorten the life of the alt and it might be easier on the alt the way it's coming online now.
It seems like the glow plugs would better if they had more voltage when running. The alternator goes from 70 amps of output to 100 amps at idle when told do so. It is actually putting out less amperage when the glow plugs are on than after they are off... kind of backwards to me.
^^^^^^^^^^ this
like i said.. after the glow plugs shut off the amperage out of the alternator goes up.
Aaron S
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Although ive never checked the amperage output of my alternator. I have had the auxiliary idle controller for quite a while and my battery voltage has always been the same as what your describing.
I cant remember why, but one cold day I put my hand on the alternator just after starting it and was surprised at how hot it was. Since then, the glow plugs are disconnected if the temps stay above 50F.
I cant remember why, but one cold day I put my hand on the alternator just after starting it and was surprised at how hot it was. Since then, the glow plugs are disconnected if the temps stay above 50F.
hwrdbd
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I personally wouldn't be concerned about sending more amps to the glow plugs once the truck is already running. They did their job and got you started, and although they stay on a bit after startup, I don't think that is their critical time. The truck is running, more than likely idling to warm up, so jacking up the glow plugs isn't going to affect much. Just the way I look at it.
TERRCO
Member
Could this be to prevent damage to the alternator? The guy that rebuilds all my starters and alternators always says please don't jump start a car with the vehicle running. He says it is real hard in the alternator. He says you can let it charge the other cars battery but before you crank turn your vehicle off.
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if the alternator has a bad diode, they'll run hotter'n a 10 pekkerd billy goat.
just running glow plugs for a minute or two after start-up won't really save/hurt much.
PsdPullerJr
Member
This got me wondering over the past couple days. Why would the PCM choose which alt to turn on? Wouldn't it just fire up both of them if it has dual setup?
Strictly Diesel
Active member
No, in a dual alt setup they do NOT both run at the same time.
PsdPullerJr
Member
Interesting. I would have thought they would both come on at the same time. What's the point of having 2 if only one runs at a time?
