MF 245 Diesel Battery/Alternator problems

Jimmy Herring · Oct 22, 2023

Hello, new member but have been reading some great post regarding the 245's.
Can someone tell me what size diode I need going to the # 1 wire on the alternator?
I do have a 3 wire alternator part #7127103.
I have noticed that some use a 63 amp but my book says a 32 amp.
I was told that I might not need the diode with the newer alternator.
Tractor serial #9A342643, 12 volt.
It was my uncles and he let several folks work on it and it has always had charging problems.
My dad and I think we have most everything wired correctly by the wire diagram.
May go ahead and put a new oil pressure switch on it just to be safe.
Any help or insight would be wonderful.
Thanks,
Jimmy

Dieseltech · Oct 22, 2023

Check the oil pressure switch first, it could be bad. I just
replaced one on my neighbors MF 175 that had gone bad.
The switch turns on both alternator and fuel gauge on diesel
tractors.

onefarmer · Oct 22, 2023

I agree with one thing added. If the pressure switch is bad it might not be able to handle the load. Who knows what else has been added to the system. I made my 175 so it activated a relay which would then energize the system, and added a few circuit breakers for wire protection.

used red MN · Oct 22, 2023

The AGCO parts book shows Delco internal regulated
alternators are OE for all applications of the 245 in
your serial number range. So you are not doing any
kind of a conversion. The number one terminal being
connected to the oil pressure switch drops the
connection to the alternator when the engine is not
running so no diode is needed to negate an engine off
draw. The other purpose for the diode does not apply
on a diesel, on a spark ignition engine it is used to stop
feed back from powering the coil when the engine
ignition is shut down not allowing the engine to stop.
But that only applies when powering the number one
excite terminal with the ignition circuit. On a gas
engine if you choose to energize the excite circuit
through an oil pressure sender the diode is not
required in that configuration either.

Jimmy Herring · Oct 22, 2023

Thank you all for the replies.
I have ordered a new switch and will replace. I'm sure my uncle never replaced it.
It's still a great tractor with lots of power.
Looking forward to many more years using it.

4play · Oct 22, 2023

The 245 is a great tractor, I hope it still has plenty of life for you to enjoy. I deleted the oil switch on mine, everything is powered through a regular ignition switch, I guess a toggle would work if security wasn't an issue. There is no need or reason to use a diode, I also converted to a delco 10si alternator.

hearnc843 · Oct 25, 2023

Here is a link to a rebuild thread on a Delco 10DN, 3 wire alternator. Ebay sells the kits. Not terribly difficult, pressing in the diodes is the most challenging task, making sure you don't break them.
10DN rebuild

MF 245 Diesel Battery/Alternator problems

Jimmy Herring

New User

Dieseltech

Well-known Member

onefarmer

Well-known Member

used red MN

Well-known Member

Jimmy Herring

New User

4play

Well-known Member

hearnc843

Member

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