# alternator wiring woes !!



## pnmng49 (Sep 7, 2014)

New owner of MF 135 diesel and new member of this forum. 

The tractor was not charging so I decided to upgrade to an alternator system.

Here is what I did:
Removed old generator and voltage regulator.
Fitted a used Delco 12si alternator onto old brackets (alternator checked out okay at auto parts store)

Wiring:
From Battery Positive to Starter Solenoid (Large Lug) to one side of Ammeter to one side of Oil Pressure Switch
From other side of Ammeter to Alternator Output (Large Stud) to #2 blade terminal of Alternator
also from this side of Ammeter to one side of Push Button Start Switch (momentary switch)
From other side of Push Button Switch through Neutral Safety Switch to Starter Solenoid (Small lug)
From Oil Pressure Switch (other side) to #1 blade terminal on alternator
also from other side of Oil Pressure Switch to Fuel Gauge to fuel sensor

Results:
I get around 13.6V at the Alternator Output (it doesn't increase as RPMs increase)
Fuel gauge is pegged to FULL (tank is half full)
Oil Pressure gauge doesn't show any pressure
Ammeter doesn't work(however, it didn't work before I created this mess)

Can someone help me fix this mess ??


----------



## pnmng49 (Sep 7, 2014)

No one can help me untangle this mess?


----------



## oldtom (Oct 23, 2010)

have you got this sorted out yet?Bye


----------



## pnmng49 (Sep 7, 2014)

No Sir. Any help would be greatly appreciated.


----------



## oldtom (Oct 23, 2010)

edrok 1.what mod si ?alternator have you got? you say that you have ran out put wire ,from large lug though amp gauge and oil pressure sender? ok run the out put wire from large lug should be marked bat to pos post on the battery in your case though the Amp gauge use a wire of 4-5mm dia and mount so that in can not rub though and short out now is this alternator off a gas or diesel engine? may have to check on drive pulley size and try putting both of the lugs on to the same stud at amp gage you saying that its not working I get back to you


----------



## pnmng49 (Sep 7, 2014)

It is a delco remy 12si alternator.
A 4mm wire connects from battery positive post to starter positive post.
From starter positive a #10 wire goes to the ammeter and then to the oil pressure switch.
I don't know what vehicle the alternator came off.
I used the pulley from the old generator.
Does it matter which side of ammeter or oil pressure switch these connections are made to?


----------



## oldtom (Oct 23, 2010)

pnmng49 said:


> It is a delco remy 12si alternator.
> A 4mm wire connects from battery positive post to starter positive post.
> From starter positive a #10 wire goes to the ammeter and then to the oil pressure switch.
> I don't know what vehicle the alternator came off.
> ...


1, the alternator needs to be at 1400-1500 rpm speed to start charging that way you need the correct size pulleys put the line-wire from +out from alternator to large stud on you starter ,amp meter will only show currant going in to the battery more on a discharged battery and less as charge comes up to full. 2, run the wire to the start switch from large terminal on the starter though neutral switch to small terminal on starter solenoid so it will not start when in gear. 3.run a wire from one of the terminal no the back of the key start switch that powers up when in the run position to oil ,fuel, gauges you may have to remove fuel gauge sender from the tank and see if its still working


----------



## pnmng49 (Sep 7, 2014)

Thanks oldtom,
The alternator does seem to be putting out some charge (I can feel the magnetic field at the back of the alternator) the volt meter reads around 13.4V not the 14.4V output I thought I needed. Regarding the non working oil pressure and fuel gauges (they both worked before I pulled the old generator) they are wired from the other side of the oil pressure switch which I thought opened and stayed hot once pressure built up. Is this correct or not?
This tractor has a momentary switch (push button) in the starter circuit. I don't think I can power the gauges from the run position because there is no run position in the start circuit that is why I tried supplying power to all gauges through the oil pressure switch but its not working. Do I have any options?


----------



## oldtom (Oct 23, 2010)

ok to increass voltage may have it change pulley should be around 2,25-2.50-1.00 of engine speed. I see is diagram:: at binatani.com under mf135 and that MF take feed from amp gauge though oil pressure you can replace amp gauge with a volt gauge so you no the charge of the battery. back in the 70 when I work for MF the tractor had a key switch Bye


----------

