Well I guess they are for trucks that idle for long times with lots of lights. Maybe good for use with the power converter. Is it hard on a hd alternator to use the converter? The question I have asked lots of dealers for years is if one goes bad, how would you know? Thats why I would want them, redundancy, keep going and fix the bad one instead of sitting who knows where broke down. The reason I didnt order it is I figured it would end up needing a belt noone would stock. Theres somthing about dealers, so dam sure of the answers they give you but dont have a clew. One answer that sticks out with me is, "your light will come on, one alternator cant charge the system"

 

I got the duel's because I wanted the redundancy and I figured with the supp. heat, heated seats and all the other electronics it would just be easier on the two instead of just one heavy duty. I would hope that we can tell if one is down and needs to be fixed, but if not I still should not have to worry for at least a couple of hundred thousand miles.

 

I had the HD alternator with mine, and that's all I would really want. Remember that turning two alternators will take more fuel, and there's one more part that can break. Sure there is some redundancy, but at what cost? Do you really plan on driving around for weeks with a warning light on after an alternator quits?

I see no benefit unless you need the capacity.

 

Is there realy a warning light or just a light when there is no charge?

 

No I would't plan on driving around for weeks with one alt down but I could, and not be stranded. I had this happen one time with a car and I was out of town. Long story short I ended getting ripped off at the dealership I had to go to. I ended up in court and won but it cost me $1800 in attorney fees. So the extra $350 for duel alt is worth it to me especially since I drive a thousand miles a week.

 

The PCM directly controls the output of both alternators, and I'm pretty sure there's programming that would detect an ineffective alternator.

 

Those of us who snowplow bought the dual alternators to help with the load from the snowplow motor (high amp draw, low speeds). I had become accustomed to seeing my ammeter dip heavily on my single alternator plow trucks (with an Optima yellow top). Hopefully no more...

 

Below is the operation for the 08 model with dual alternators. Note there are separate DTC's for primary and secondary alternators too. But also note the secondary is only used when the primary is at max; so not really balancing the load between the two. Then again, maybe Ford had a better idea, with the newer models?

From Workshop Manual:
Principles of Operation
The PCM controlled single/dual charging system determines the optimal voltage setpoint for the charging system and communicates this information to the voltage regulator. This system is unique in that it has 2 communication lines between the PCM and the generator/regulator. Both of these communication lines are pulse-width modulated (PWM). The generator communication (GENCOM) line communicates the desired setpoint from the PCM to the voltage regulator. The generator monitor (GENMON) line communicates the generator load and error conditions to the PCM. The third pin on the voltage regulator, the A circuit pin, is a dedicated battery voltage sense line.
The generator charges the battery and at the same time supplies power for all of the electrical loads that are required. The battery is more effectively charged with a higher voltage when the battery is cold and a lower voltage when the battery is warm. The PCM is able to adjust the charging voltage according to the battery temperature by using a signal from the intake air temperature (IAT) sensor. This means the voltage setpoint is calculated by the PCM and communicated to the regulator by the GENCOM circuit.
The PCM simultaneously controls and monitors the output of the generator. When the current consumption is high or the battery is discharged the PCM raises engine speed to increase generator output.
In dual generator systems, the PCM keeps the secondary generator in a standby state where it does not generate current unless the primary generator is generating full power and more current is needed to support the vehicle loads. The PCM monitors the output of the primary generator and adjusts the control setpoint of the secondary generator to cause it to provide additional current when needed.
To minimize the engine drag when starting the engine, the PCM does not allow the generator to produce any output until the engine has started. The PCM turns off the generator during cranking to reduce the starter load and improve cranking speed. Once the engine starts, the PCM slowly increases generator output to help establish a stable engine speed.
The PCM controls the charging system warning indicator by sending a message over the high speed CAN to the instrument cluster (IC). The PCM turns the charging system warning indicator off when generator output begins. The charging system warning indicator is also illuminated by the PCM whenever the key is ON with the engine OFF.

 

I am sure there are applications where the duel alternators are what is needed. When I ordered mine I thought the heavy duty one should do everything I need. It also seemed to me most times an alternator goes bad it is a bearing so with two you double your chance of a bearing going out and destroying the fan belt and stranding you. Just my thoughts.

 

I know I only have one alternator but not sure if it is an "HD" model.

How does a person tell if they have a "HD" alternator ?
Will it say on the window sticker ?

Can a person add the second one later if needed/wanted or does it have to be ordered/built with it ?

 

Here is a thread where we discussed more about alternators. As I mentioned in the thread, for most people, dual alternators will be overkill. For those of us who plow, run salters, external lights and those wonderful tush warmers -- the dual alternators are a great way to manage the load.

Surprisingly, in all the years I have plowed, I have never gone through an alternator. Batteries on the other hand are a different story.

https://www.ford-trucks.com/forums/1...ternators.html

 

It was included in the snowplow prep package and as a standalone option. If you have that package it will be bundled and if it was ordered as a standalone, it will be called out on the sticker.

 

I have have high frequency reading a fault high and it's saying I have 63.47 volts to pcm and that is giving erratic turbo egt and fuel psi reading if it was really pegging boost out at idle the hose would be hard and she would role coal with reading in i took alt off but not sure now it tested OK but that doesn't test frequency so it either alt a wire or pcm I have the manual so maybe I'll figure it out need to get in side snow hit me if any one knows where the wire issues are that's what alt shop guy said when he had another guy asking same thing on his new truck ford makes impossible to get warranty work 100s of miles away to dealer that will touch it lemon truck ford left me hanging after cash back deal it's had so many problems engine head air line broken trans dip stick I'm about pull box and set it better truck