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My 2001 f350 7.3 came equipped with dual alt ambulance package system. I am looking to replace both alternators but not sure on what amp each produces so u can replace?
Thanks
Rob
The are both 110A alternators. The only difference between the two is the clocking for mounting. They have the same guts and output.
Just make sure if you are replacing both you get one for each position. Everybody has the upper alternator but make sure you get one specifically for the lower alternator position otherwise you won't be able to hook it up after it's mounted. If it is not an option call whoever you are ordering from and they should know what you need.
I am all about rebuilding stuff if you can however how would you know what’s wrong with it? I feel this is out of my wheel house.
I rebuilt one years ago, don't even remember what it was in but the rebuild kit came with parts and no soldering was required. IIRC there was a diode in there and a couple of things they called brushes. The brushes weren't really brushes but little blocks of something like copper. The failure was that the brushes were worn out and they just kind of sat in there under pressure from a spring. The kit came with two toothpick type things that held the brushes back for assembly and after assembled they got pulled out and the brushes rubbed up against the part that goes 'round. I might not have even used the diode, it's been too many years and too many miles since then.
Do you truly know both need to be repaired? The computer uses the top one on my 2000 as the main alternator. The lower alternator is used as a backup, so it really never gets turned on. My lower did eventually fail at about 325k miles. The upper went at around 250k miles, but you can drive with the upper not working, as long as it's not physically impaired. The computer just doesn't turn it on.
There's also pulley size difference so that the lower one is under driven.
It was recommended to me that if I replace (or rebuild) one I should do it in pairs similar to batteries. Since I wanted to upgrade I got matching units to install (clocked for their respective postion of course).
I rebuilt one years ago, don't even remember what it was in but the rebuild kit came with parts and no soldering was required. IIRC there was a diode in there and a couple of things they called brushes. The brushes weren't really brushes but little blocks of something like copper. The failure was that the brushes were worn out and they just kind of sat in there under pressure from a spring. The kit came with two toothpick type things that held the brushes back for assembly and after assembled they got pulled out and the brushes rubbed up against the part that goes 'round. I might not have even used the diode, it's been too many years and too many miles since then.
The brushes are carbon. They are in most electric motors. Or at least used to be. Most tools, i.e. battery powered drills and such are brushless.
Yes, on my truck (2000 F250) the lower alt never really gets used, as I don't have any heavy electrical loads on it. The computer will use the top one first. If it sees that the top one isn't working, then it turns on the lower one. That happens about 40 seconds or so after start up. It's a different voltage change than when the glow plugs turn off. I run a volt meter on my trucks 24/7, so I'm used to seeing the voltage do certain things. When it doesn't, I start investigating to see why. That's how I found the upper alternator had failed on my truck. But because the lower was now working, I did not have to fix the upper immediately. I actually waited almost a month before I got time to swap out the upper, with the lower taking over duties. The computer always tried the upper first, then turned on the lower. I could watch it happen on the volt meter.
I bought the truck new in Nov 99 and it's got almost 375k miles on it, so I've been watching that meter for a long time.
Yes, on my truck (2000 F250) the lower alt never really gets used, as I don't have any heavy electrical loads on it.
Have you rewired your truck?
Or is your truck's charge wiring stock?
If your truck wiring is stock, how did you determine that your lower alternator "don't have any heavy electrical loads on it"... when both alternators are connected to the same charging circuit?
Originally Posted by U9000
The computer will use the top one first. If it sees that the top one isn't working, then it turns on the lower one. That happens about 40 seconds or so after start up. It's a different voltage change than when the glow plugs turn off.
If you say your lower alternator turns on "about 40 seconds or so after start up", and, you say that event "is a different voltage change than when the glow plugs turn off", then
1. When did your glow plugs turn off? Before the 40 seconds, during the 40 seconds, or after the 40 seconds?
2. What was "different" about the "voltage change" when comparing the lower alternator turning on, versus the glow plugs turning off? Quantify exactly what was the change in voltage that you observed on your 24/7 volt meter?
Originally Posted by U9000
I bought the truck new in Nov 99 and it's got almost 375k miles on it, so I've been watching that meter for a long time.
I respectfully appreciate that you've had your truck for nearly 20 years, but the way you are describing how your dual alternators work is a little different than the way Ford describes how dual alternators work. Your description of your experience is also different than how the originally equipped dual alternators work in my truck, which was also built in November of 99, and which I've owned for just about as long as you've owned yours. Hence the specific questions, because this thread archive, along with all of us who have or are interested in the dual alternator (aka ambulance) package for this application, are best served by having the most accurate understanding of how they work.
Ford describes how the dual alternators work in Section 414-00-2 (Charging System - Description and Operation) of the Workshop Manual, where Ford states: "The PCM only controls the lower generator by turning it on or off... only when the glow plugs are commanded on by the PCM to avoid possible damage (excessive voltage) to the glow plugs."
With this in mind, it is easy to understand observing a change in voltage when the glow plugs are commanded off. And Ford states when the glow plugs are commanded off, the lower alternator is turned on.
Your description implies something else entirely. You imply that the two events, glow plugs off, and lower alternator on, are observably distinct events distanced with time. You further imply that the lower alternator doesn't see the same loads that the upper alternator sees during use, when both alternators are on and connected to the same charging circuit. Since the only "control" that the PCM has over these alternators is turning the lower alternator on or off, and since the lower alternator is only turned off when the glow plugs are on, your earlier statement that "The lower alternator is used as a backup, so it really never gets turned on" appears to be a misunderstanding of how both alternators work together.
Just had my 99 7.3l dual alternator leave me stranded.. I had left for a two hr drive at night and got 20 miles down rd and seen my voltage drop drastically on gauge and lights dimming. In less than ten miles I had to pull over.. truck was dead and batteries to low to restart .. I did have a gen and battery charger with me and boosted for a hr.. then ran the gen and charger and limped it back home..
now when I got it home, my batteries and lights were very low, truck died idling in front of house..
I then left for the night on charger and started up in morning.. I quickly could hear the top alternator was wore out and pully jumpin around like the internal bearings shot.. go back into truck and it was chargeing fine, like there was no problem.. I drove truck for half he to lordco and replaced top alternator 360$$ ac delco, now truck is starting faster than it ever did and no problems..
so my question is is my lower alternator working.. it did charge fine the morning before replacement.. I had just taken it to be the top alt was possible working again, but reading the replies in this thread, maybe ecm said to start lower .. I only replaced top
Is there a way to check bottom and if I pulled over quick enough on the rd, after noticing low volts would of ecm seen the problem and used bottom alt.. don’t want to be caught like this again at 20below, and thinking I should have a spare on hand if need be.. thanks for help
