MF-65 diesel generator to alternator wiring.

[jaka]

After obtaining some excellent advice to my questions I've drawn out my wiring plan to hook up my 3-wire alternator. I would appreciate any comments on correctness. I plan on wiring the light switch on the always on side so that they can run off battery if needed.
My old Massey only has an ammeter and an Oil Pressure gauge.
See attachment.

 

[Down South]

I haven't looked at your diagram.

But with a 3 wire, 10si internal regulator alt. The easiest is to pick up a replacement plug at the auto parts store.
It has a larger red wire and a smaller white wire. The red goes to the batt post on the back of the alt, with the batt main (10ga) which goes to the amp gauge.
The white goes to the oil pressure switch on the engine. Turns on and off with the oil pressure.

Ds

 

[Soundguy]

well.. a few things.

1, the #2 sense line can be safely shunted right over tot he charge stud.

in a car with 45 miles of wire.. sure.. measure vdrop at the battery terminal. in a tractor with 8' of wire... why?

also.. if you want your center 0 ammeter to ACTUALLY read net charge and discharge.. you need the output of the alternator and ALL electrical loads like lamps and ignition on the SAME side of the ammeter. the other side of the ammeter has 1 connection.. to battery hot.. or solenoid battery hot.

that way charge thru the ammter shows positive.. discharge thru the ammeter shows negative.

during normal operation. alt carries loads and sends charge to battery.. thus you see a positive deflection when charging/running with lamps on.. but when shut down, swings negative showing lamps discharging bat..

also.. most alts need 350 rpm to start turning on.. if oil pressure comes up FAST in that machine.. and or start is quick.. you may not be powering #1 long enough .. if it is as with most older machines and cranks a second or 3 and takes another for OP to come up.. should be ok.. i still think I'd have that feed off run not start.. start will stop having power on it as soon as you release.. run will maintain power any time key is on.. when key off.. it's dead. adn #1 will be open once op comes up anyway.. so my vote is run op feed thru run... just me..

soundguy

 

[ThomasH]

What Soundguy just said is exactly correct...

 

[The kid]

If your upgrading the charging system, why are you staying with an ampmeter and oil pressure power switch? Won't the alternator's output exceed the ampmeter's input under certain conditions? My switch has acc to the left, off, then run, momentary start. Let's just say someone left the keys and a light on. Battery run down. You jump it and start it up. The alternator outputs to maximum to the battery exceeding the amp rating of the ampmeter. Is that possible?

 

[Soundguy]

non inductive amp meters are shunt voltmeters.

meaning.. inside that ammeter is a bar of metal.. as current passes thru that bar ( shunt ).. a very slight voltage drop occurs.. that is displayed as an AMP reading on a calibrated scale.

I have only once ever heard of a shunt failing. even if you are out of range on the meter.. the shunt should pass the current.

I'd be more worried about the WIRE from the alternator stud to the meter..

most people wire 14awg!! you are lucky to get 10 or 8. the shunt inside the meter should handle what 10 or 8 will.

initial high charge rates will drop off quick too.

also.. charge rate will depend on alternator. you can get old delco 10 si that are 30's and 40's amp range etc..

lotsa variables.

but yeah.. theoretically if you had some monster CCa battery int here that was near stonne dead, and a high perfromance 90 or 120a special delcotron .. you might start load testing the the wireing and possibly the ammeter. I'd suspect the wires and crimp or soldered connectors to go befor ethe ammter does.. unless the wires are larger than 8awg. Can't tell you how many 'smoked and burnt' wire harni i have repalced on machines I bought where there was obviously dead short of wire harness to chassie and let bat discharge thru ammeter to burn harness, and yet.. still have a working ammeter...

not saying it couldn't happen.. just saying i trust the ammter to run out of range a bit before you would experience any issues.

 

[jaka]

Lots of good info here to digest and I defer to those who have the knowledge. After reading the comments I will change the hookup for the lights. I also plan on replacing the ammeter with a voltage meter. I noticed that my oil pressure gauge is just a tubing connection so cant use that one for the exciter wire. It's a good point on the jumper wire to the Bat terminal since I only have about 6' feet of wire involved in going to the positive post on the battery. Thanks for all the good comments.

 

[Soundguy]

be aware that you can't repalce a ammeter with a voltmeter without changing the wireing.. ammeters are a series device.. volt meters are a parallel device.

if your ol pressure setup is not a sender /lamp, and is a mechanical cap tube.. you will need an ign switch exciter.. preferably use a diode for reverse current isolation or an accy type switch.

 

[CNC Dan]

if your ol pressure setup is not a sender /lamp, and is a mechanical cap tube.. you will need an ign switch exciter.. preferably use a diode for reverse current isolation or an accy type switch.

You can tee in an oil pressure switch if you want to have both gage and switched alt. feed.

 

[Soundguy]

sure can.. but that is getting to be one big oil contraption on the side of the engine waiting for a branch to come along.

If going this route I suggest using a plain cap tube from the puckup and routeing it to a safe place unde rhte hood then t off there.. unless the piclup spot on the block is sufficiently shielded that a t and nip could go in and be out of harms way.