275, amy wiring changes for a modern alternator?

[petebert]

New to me 275 with what appears to be a dead alternator. I tried jumping the wires on the oil pressure switch and it didn't change anything.

Does anything need to be changed since they're self exciting now? I've got an original wiring diagram. Someone before me made a mess of the wires so I'll probably go everything.

Looks like the wire from switch to alternator with the diode should no longer be needed. Looking at the diagram it looks like power is supplied to the fuel and temp gauges when the pressure switch activates? I think I read somewhere to keep the oil switch otherwise it will keep power supplied to those gauges 24/7 ?

 

[Jim.ME]

(quoted from post at 22:38:40 09/15/23) New to me 275 with what appears to be a dead alternator. I tried jumping the wires on the oil pressure switch and it didn't change anything.

Does anything need to be changed since they're self exciting now? I've got an original wiring diagram. Someone before me made a mess of the wires so I'll probably go everything.

Looks like the wire from switch to alternator with the diode should no longer be needed. Looking at the diagram it looks like power is supplied to the fuel and temp gauges when the pressure switch activates? I think I read somewhere to keep the oil switch otherwise it will keep power supplied to those gauges 24/7 ?

It sounds like you are thinking of installing a one-wire alternator. To be clear. How many wires are connected to the current alternator. Only one on the output post (a one-wire alternator), or one on the output post and two to spade terminals (a three-wire alternator)? (Either alternator may or may not have a ground wire to the case which is not counted.) There is no real gain in installing a one-wire alternator, especially if the wiring is there for a three-wire alternator. In fact, the three-wire ones are less likely to cause battery drain and often start charging easier at a lower rpm. In either case installing the right width pulley for the belt is important and using a small diameter pulley usually improves performance.

Depending on what alternator you are looking at installing, the one-wire conversions of the 10SI/12SI three-wire alternators are just that, regulator conversions to one-wire, not any more modern in my thoughts.

AS to your oil pressure switch question. Many Massey Ferguson diesels did not have an ignition switch to control the power to gauges and charging. Given they used mechanical fuel shutoffs a switch could be forgotten, left on, and the battery drained. That is the purpose of the oil pressure switch here, the engine stops, oil pressure goes to zero, and the power is cutoff to the electrical accessories. You need to keep the oil pressure switch, or you will need to rewire those items to add a control switch for those items.

Just my thoughts, others may have different ones.

 

[petebert]

I'm looking at the 3 terminal 10SI which Delco says come with a BAT, a half voltage R and a full voltage 1.

The alternator on there now is a 72amp delco that has a jumper going from BAT to 2 and the wire from 1 leads back the instrument panel presumably but I haven't opened it up yet to see where it ties in.

 

[Jim.ME]

(quoted from post at 10:38:29 09/16/23)
I'm looking at the 3 terminal 10SI which Delco says come with a BAT, a half voltage R and a full voltage 1.

The alternator on there now is a 72amp delco that has a jumper going from BAT to 2 and the wire from 1 leads back the instrument panel presumably but I haven't opened it up yet to see where it ties in.

That sounds like the same alternator you have on it now, the new one should hook up the same. The wire on the #1 (R) terminal would be the one with the diode (prevents feedback into the system from the alternator) in it, which excites the regulator to start it charging. The #2 (F) terminal uses feedback from the battery post of the alternator to regulator to monitor system voltage.