Page 1 of 1

computer controlled alternator with MS2

Posted: Tue Sep 11, 2012 9:26 am
by olaaf
Hi All

On my ford 4.6, the PCM controlled the alternator. As far as I can tell, one of the 3 pins went to the indicator light on the dash, one went to the “sense” line, connected to 12v, and one went to the PCM.

What is the function of the PCM line, and can I just lift it and not worry? I think I blew out the logic circuitry on my alternator, and I ran with the 3 pin plug unconnected. The battery is over-charging, and I need to rev the engine a little upon start up to kick in the alternator..

Any thoughts?

Thanks
olaaf

Re: computer controlled alternator with MS2

Posted: Tue Sep 11, 2012 9:50 am
by Matt Cramer
I've seen several different ways of doing this. On some cars, the ECU just switches the voltage regulator from high to low voltage mode. On others, it directly controls the alternator field winding.

Re: computer controlled alternator with MS2

Posted: Wed Sep 12, 2012 2:20 am
by olaaf
Hi matt

What do you generally recommend people to do with PCM controlled alternators?

thanks
olaaf

Re: computer controlled alternator with MS2

Posted: Wed Sep 12, 2012 4:53 am
by Peter Florance
olaaf wrote:Hi matt

What do you generally recommend people to do with PCM controlled alternators?

thanks
olaaf
I think it depends on how the alternator functions. That will determine how to control it. Sometimes the wiring diagram will show the internal parts of the alternator. That will help.

Re: computer controlled alternator with MS2

Posted: Wed Sep 12, 2012 6:04 am
by Matt Cramer
Precisely - you need to figure out what the PCM is doing to control the alternator first.

Re: computer controlled alternator with MS2

Posted: Wed Sep 12, 2012 7:56 am
by elaw
olaaf wrote:I think I blew out the logic circuitry on my alternator, and I ran with the 3 pin plug unconnected. The battery is over-charging, and I need to rev the engine a little upon start up to kick in the alternator..
That may be your problem right there. Regardless of what you do with the other two wires, do NOT run with the "sense" line disconnected! When you do that, the alternator may think the system is getting 0 volts and increase its output to compensate... thus overcharging the battery.

I'd try connecting the sense line to (in order of preference) the +12 "main junction point" if your car has one, or the alternator's output terminal, or the battery. Connect an indicator light to the light terminal and the ignition +12 (that'll eliminate having to rev the engine to get the alternator going), and go from there.

Re: computer controlled alternator with MS2

Posted: Wed Sep 09, 2015 4:47 pm
by alga
Here's some info about the Ford alternator control: http://www.napaechlin.com/Ford-PCM+Cont ... ntent.aspx
http://ww2.justanswer.com/uploads/djenn ... 48_alt.png

The two control lines are the voltage command from the PCM to the alternator (voltage encoded by frequency or PWM), and alternator reporting its electrical load with a PWM signal. There's no provision even in MS3 to output an arbitrary frequency, is there?

Re: computer controlled alternator with MS2

Posted: Sat Feb 24, 2018 1:09 pm
by nginmu
I am using the following alternator from a Ford Focus TDci Mk1:

F03093 / C870 / 12A690 / O5 GENERATOR

ACTUAL PART NOS
MS1022118070
A115IM
?M5T1030[0/O]BC

MAGNETI MARELLI

It has the following Smart Charge pins:

pin 1 4-EB6 (GY) DATA LINK, BUS POSITIVE - ALT COM (alt command?) - Gray Wire
pin 2 5-EB6 (BU) DATA LINK, BUS NEGATIVE - ALT MON (alt monitor?) - Blue Wire
pin 3 30-BA10 (RD) PERM POSITIVE

Would I be correct in thinking that if I left pin 2 open (because I am not using a Ford Smart Charge Powertrain Control Module), connected pin 3 to permanent +12V (as per every Focus wiring diagram I've come across), and then connected pin 1 (which would be the alternator command wire from a Ford PCM) to a stable permanent +12V also, the alternator would would read the stable +12V on the command input as a 100% Pulse Width Modulation signal and assume a Ford Smart Charge Powertrain Control Module was telling it to output maximum power possible at all times..

I'm aware that if that *is* how it works, then in a normal, standard realworld battery charging situation there would be allsorts of attendant problems with doing this such as boiling the battery etc. I'd just like to try and find out if I'm understanding correctly the practicalities of how this Ford alternator control system works.

Is it more complicated than just calling pure +12V a valid 100% PWM signal? Is the valid signal a different voltage such as say 5V, is there a particular range amplitude and frequency of PWM pulses at play etc?

Can anyone point me to any datasheets for the Ford alternator data specifications / parameters / protocol descriptions?

Re: computer controlled alternator with MS2

Posted: Sat Feb 24, 2018 1:33 pm
by nginmu
Apologies for the potential double post. Upon a little more searching I found some great relevant info here: http://www.msextra.com/forums/viewtopic ... 31&t=58716