Farmall M alternator

mailman1 · Jan 2, 2018

In the process of getting my M to start better in the last few days I got to thinking about if the 12 volt conversion that I had done some 20+ years ago was charging. I looked and found that the alternator is a Delco-Remy 1100696, 42 amp. 7D18-12v neg. ground. I am going to take it in this A.M. and have it checked to see if it still charges, but my question is most all of the conversion kits that I have found come with a 63 amp. alt. When I did the conversion I still used my original 6 volt coil and 6 volt starter with a resistor. If I remember right I copied the wiring diagram from my neighbor who was a IHC mechanic at the time. Also a lot of the videos and articles I have watched and read mention using a 12 volt coil and a 60-0-60 ammeter. Should I change my ammeter from a 30-0-30 to a 60-0-60 as I have always noticed that it never did show the 30-0-30 to be charging?

henryv11 · Jan 2, 2018

Just put a volt meter on the battery with the tractor running and measure the voltage
should be 13.9 or so. if it is the alt is OK

rustyfarmall · Jan 2, 2018

42 amp is plenty. In the early days of alternators on cars, most were about 35 amp or less. 60 amp and up is only if there are a ton of accessories that consume electricity.

DeltaRed · Jan 2, 2018

No reason to change meter,unless it is broken.Your tractor will never draw that much power.I have 5 of the 63 amp one wire alternators on H/M tractors here. they have the 'old' original meter.No issues.

tractorguy2 · Jan 2, 2018

I have a 30-30 meter on my conversions. They only charge 30 amps
when the battery is almost dead. The six volt coil is fine. The
old IHC coils are better than any new 12 volt coil. I would
check the running battery voltage first.

My guess would be starter brushes are wore out.

DeltaRed · Jan 2, 2018

Yep,a lot of those old starters need serviceing these days.The starter will still spin,but will turn slow and draw a huge amount of amps.Best to take it to local rebuilder.Also many times the battery cables are too small,and corroded.

mailman1 · Jan 2, 2018

I had the alt. checked this morning at NAPA and found out it was toast, and I can get a 63 amp. for $50 so that's probably the way I will go. Is there a way I can check my ammeter to see if it's good or not?

BarnyardEngineering · Jan 2, 2018

What was the ammeter showing?

If it is showing a large negative value while the tractor is running, you missed the step where you swap all the wires on the ammeter because you changed from positive ground to negative ground.

If it is not showing anything, the electrical system is not wired correctly.

If it is showing a slight discharge, either the alternator is not working or the electrical system is not wired correctly.

You need to do some troubleshooting before you start throwing money and parts at it.

old · Jan 2, 2018

My self I buy alternators to fit a 1980 Chevy pickup truck. No power any thing no AC and there in the 40 amp range or so. A tractor has no need for a higher amp alternator since 99% of the time all your doing it running the engine and so you have no lights on or other such draws. I buy my alternators from O'Reilly's for 2 reasons. #1 life time warranty and #2 to only other parts store is auto zone and they well I'll just say they are lucky if they can find a hole in the ground before stepping into it

rvirgil_KS · Jan 2, 2018

The amp rating of an alternator is at maximum rated load and maximum rated rpm, neither of which you will see on a tractor.

recharging battery after starting, 4 amps for distributor ignition and 3 lights you will seldom exceed 30 amps and go down as battery charges. If that is the demand, a 35,43, 67 or 110 amp alternator will all only put out enough to meet the 30 amp or less demand.

AlinMO · Jan 2, 2018

(quoted from post at 11:02:26 01/02/18)
I had the alt. checked this morning at NAPA and found out it was toast, and I can get a 63 amp. for $50 so that's probably the way I will go. Is there a way I can check my ammeter to see if it's good or not?

Turn on your lights. Ammeter should show discharge. If it shows charge, your ammeter wires need to be reversed. When the tractor starts, the ammeter will show a positive charge that tapers to almost zero after battery is fully charged.

gab · Jan 2, 2018

I put a 42A on my Super M because that's what I had laying around. Unless you're installing A/C, power windows/door locks and a rear defogger you don't need a 63Amp. My 30 amp gauge works fine.

mailman1 · Jan 2, 2018

I found a 55 amp. alternator in my shed this afternoon that's just like the 42 amp. that was on there so I'll check it out in the morning and see if it good or not then go from there.

used red MN · Jan 2, 2018

To check the amp gauge do as AlinMO suggested turn on your lights with the engine off. Two
headlights and a rear light will definitely make the ammeter move if it works. Basically the
ammeter should have a wire that connects one post to the positive battery terminal. The other post
should have the alternator lead, ignition power and light power all on it.

Farmall M alternator

mailman1

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henryv11

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BarnyardEngineering

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