Alternator Wiring

hearnc843

Member
I have a MF 175 that is having some electrical issues. I recently rewired and fixed all of the lights. It turned out the old glass tube fuses were rusted real bad, and wires were heating up, voltage was low- it was a mess. After putting in new blade fuses, acid now leaks everywhere when the tractor is running, leading me to believe the alternator is overcharging the battery.

I not been able to locate a wiring diagram with an alternator- this tractor originally came with a generator (I bought it with the alternator already on it)

I have drawn up this rough sketch of the current schematic, and included a picture of the alternator. The "BAT" terminal on the alternator is connected to one side of the ammeter, and the other side of the ammeter is connected to the battery via the starter solenoid top connection. Should this "Bat" side of the alternator be going through the regulator before connecting to the battery?

Any help is greatly appreciated.

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Do you have a multimeter? I just installed a new alternator on my 135 and it was reading about 17V from the alternator BAT terminal to ground, and about 14V across the battery terminals (about the max you'd want to see at the battery)

I have a low-res 135 wiring diagram but it looks like "the other side of the ammeter is connected to the battery via the starter solenoid top connection" is correct. I can't make out what terminal the other side of the ammeter is connected to. I'll hopefully be getting my shop manuals this week and will upload a better diagram.
 
Thanks for the response-

I just metered the alternator, I got a over 17V. The battery is getting the same readings- a little over 17V. I cranked the throttle a bit, and the voltage kept going up. At 1500 RPM
it was at 18V. I cut the tractor off, but the meter was till creeping up (almost to 19V), I didn't want a battery acid mess again. If I keep the RPM at about 1000, the voltage at the
battery will stay around 12V.

Could I have the belt on to tight? Or do these alternators have internal regulators or something? I am getting way to much voltage.
 
(quoted from post at 13:28:36 09/22/20) Thanks for the response-

I just metered the alternator, I got a over 17V. The battery is getting the same readings- a little over 17V. I cranked the throttle a bit, and the voltage kept going up. At 1500 RPM
it was at 18V. I cut the tractor off, but the meter was till creeping up (almost to 19V), I didn't want a battery acid mess again. If I keep the RPM at about 1000, the voltage at the
battery will stay around 12V.

Could I have the belt on to tight? Or do these alternators have internal regulators or something? I am getting way to much voltage.

Looks like you have a 10DN alternator, external voltage regulator. Either the regulator isn't working or isn't wired right.

My alternator wiring looks different than yours - but I haven't verified mine is right either. I'm going to be tracing my wires this weekend (my ammeter isn't working but battery is charging) so if you don't get any other help, I'll report back.
 

You can simplify the wiring a LOT with an internally regulated alternator, but I'm not sure I'd replace a working alt just to simplify the wiring.

That said, I'd ditch the ammeter in favor of a voltmeter. It's a bit more useful in my opinion.

I can't help you on the regulator wiring, I pulled mine off when my genny died, upgraded to an internally regulated tach drive alt. and ran a heavy automotive battery cable directly to the battery and ground.
 
No, that diagram is not good.

My suggestion, upgrade the alternator to an internally regulated 10SI. You can get them with a tach drive if you want to keep that feature, otherwise that is the most common, economical alternator in the world! It is the same mount as the one you have.

Assuming yours is diesel, here is a better diagram that shows the simplified internal regulator alternator. Scroll down to the second diagram.
175 Diagram
 
I would rather not buy a new alternator, I know this one works. I found this diagram when searching- it is exactly how my wiring is done. Does this look correct?

I have been reading about the 10DN, and it seems that the "F" is what regulates the output of the alternator. If this is the case, them I am thinking that my regulator is bad, but the wiring is correct.(as long as that diagram looks good)

And it seems it is ok if the "R" remains disconnected. From what I have read, the "R" was a DC channel for accessories that required DC.
175 diagram
 
Thanks ptfarmer- I am going to run these tests tomorrow. Wiring matches what I have on my tractor, so it must be the alternator or the regulator that gone bad. I have heard about the Big Dean CD, how can I get a copy? Does he sell them?
 
Thanks everyone for the help. It was the regulator that was bad. It has probably been bad for a while, but I never noticed because the battery was always dying. The rusted up old school glass tube fuses were arcing, causing undercharging and low voltage amperage in the whole system. When I fixed these with the new "blade" style fuses it unmasked the problem- bad regulator so the whole system was seeing the 17-18V max of the alternator. Hopefully this aftermarket regulator lasts- I dont believe Delco makes them anymore.
 
(quoted from post at 17:20:49 09/26/20) Thanks everyone for the help. It was the regulator that was bad. It has probably been bad for a while, but I never noticed because the battery was always dying. The rusted up old school glass tube fuses were arcing, causing undercharging and low voltage amperage in the whole system. When I fixed these with the new "blade" style fuses it unmasked the problem- bad regulator so the whole system was seeing the 17-18V max of the alternator. Hopefully this aftermarket regulator lasts- I dont believe Delco makes them anymore.

Glad you got it worked out. I'm having the same problem now (battery overcharging). Did you go with a modern solid-state regulator replacement or an original electro-mechanical type? Going to pull my voltage regulator apart and try cleaning the points.
 

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