Ms3x GM LS alternator control

[5.3LS10]

I am looking at having the megasquirt control my alternator. What I have had to do.in the past is run a 12v wire either through the dash bulb or a resistor and then to the terminal on the alternator. I believe this is referred to as L or lamp mode. So I need an ms3x output to put out 12v and run inline to a resistor and then to the alternator.

I remember reading in the manual that you can add a 12v wire to the ms3x to output 12v I think on nitrous out or something.

Is there a recommended wire to use or way to configure this?

Thanks
Shane

[prof315]

A standard built MS doesn't have any voltage outputs other than 5VRef, you would need custom circuits for it. The 12V nitrous circuit you mentioned is an INPUT. Also you only want/need/use MS to control the alternator if it is controlled by the factory ECU like most 90's and up Chryslers, 99 and newer Mazdas (Miatas in particular) and other late model cars. GM didn't start doing computer controlled alternators till the mid 2000s. The way you described in your post is the proper way to control a typical GM Alternator.

[5.3LS10]

A standard built MS doesn't have any voltage outputs other than 5VRef, you would need custom circuits for it. The 12V nitrous circuit you mentioned is an INPUT. Also you only want/need/use MS to control the alternator if it is controlled by the factory ECU like most 90's and up Chryslers, 99 and newer Mazdas (Miatas in particular) and other late model cars. GM didn't start doing computer controlled alternators till the mid 2000s. The way you described in your post is the proper way to control a typical GM Alternator.

Thank you for the response. I may have the megasquirt ground a relay and have the path through the relay power the alternator r so that I have the control of waiting a few seconds after start up to energize alternator.

[jsmcortina]

Find attached some draft instructions that may help you.

James

[5.3LS10]

Find attached some draft instructions that may help you.

James

James quick question.

For "Basic ECU Control" on page 56 is the idea that when the ECU grounds the connection so current flows through the ECU and not the alternator and therefore does not excite the alternator?

When the ECU no longer grounds the connection then current flows to the alternator and excites it to start charging?

Just making sure I understand what it is doing.

Also can I use the Boost output for this?

Thanks
Shane

[jsmcortina]

Yes to all of that.

James

[5.3LS10]

Thanks James.

I will get this wired up tonight or tomorrow and test.

[5.3LS10]

James,

Will a 1/4 watt resistor be fine?

[nathaninwa]

I've got a truck style 4 wire alternator that measures in at like 10k ohms. I'm looking to wire this up to sense load as I want to raise target voltage from 13.5 to 14.5. Since I use only the L terminal now with a lightbulb to start charging, megasquirt won't care that it's not controlling that, I can just pick an output and leave it wrapped up, but only wire in the F terminal?

Seems like a basic question, but not sure if ms is able to see the F terminal not used and then not charge correctly

[jsmcortina]

I've got a truck style 4 wire alternator that measures in at like 10k ohms. I'm looking to wire this up to sense load as I want to raise target voltage from 13.5 to 14.5.

How are you going to change the target voltage?

James

[nathaninwa]

Maybe I'm not 100% sure. When I turn on alternator control it gives me a target voltage set point. Figured it did it through the control wire?

I would just like to raise the target voltage point in the end is all

[jsmcortina]

To my knowledge, the voltage is not adjustable on the 4-wire. If it is, I've not found out how.

James

[nathaninwa]

I need to finish my testing. I pulled the gas tank to mount my chute. Should be tonight or tomorrow

My initial testing I used the S wire tied to the charge lug and voltage stayed at 13.5, I then put a 470 ohm resistor in the S line and my voltage jumped to 14.5v

[jsmcortina]

Yes, fudging the Sense voltage should do it, but I'm not aware of a computer controlled method.

James

[nathaninwa]

Just to update this. I used a 1/2 watt 470ohm resistor on the S wire between the charge lug and connector. Voltage starts out near 15.5 volts and drops to 14.4 after about 3 mins of idling maintains that through the rev ran

A 330ohm resistors gave me 14.2 volts

Since the coil packs and injectors are close enough, you could use that power as the S input so voltage is maintained at the coils My wiring is short/fresh enough I'm not seeing any voltage drop but I have on others

[nathaninwa]

Attacking my alternator problem again, once mine gets hot it almost quits charging

So it's going to get warrenteed and I'll get the later 2 wire pwm unit. Looking at the pdf looks like I can hook up the L terminal to pwm output, but what happens to the F terminal? Is it left unhooked or is it still hooked to my charge lamp?s

[nathaninwa]

I was able to get this two wire pwm alternator bolted up today. Pulley center lines and case diameters are different so it took some futsing and a weebit longer belt. But it's ready to test in the morning

It's an 07 Tahoe with the 5.3 motor, DR44 alternator

Looks like I'll be trying closed loop field control using either pwm3 or injector I for output to the L terminal. Does this get setup as normal or inverted since it's looking for a 0-5v signal?

And I'll wire in the F terminal to 12v in