Ford 4100 alternator

4100

New User
Can anyone ID this alternator. Looks like I may need to replace. Or modify wiring.
mvphoto16361.jpg


mvphoto16362.jpg
 
Looks like the factory Motorola unit. I would clean up that rusty terminal with the large red wire going to it and see if that helps.
 
12 volts from that terminal. Not sure if other wires are connected corectly. Thinking of rewiring and maybe with another alternator.
 
It's a 32 amp Motorolla. Expensive little bugger. I'd check to see if the reg or the battery sensor is bad first. Basic test... full field the alt by hooking a jumper wire from a Bat source to the top blade with the blue/red wire. If it makes 14v while full fielded, the alt is probably OK. Those things are somewhat notorious for having bad battery sensors and bad regulators. The bat sensor is in the bottom of the tray. If you unhook the wires and jumper the wires together in the harness and it charges, then replace the sensor. If it doesn't charge, I'd probably replace the regulator... after having inspected the wiring between all components. Those connections on the alt are not doing you any favors either...

Rod
 
Rod, the Motorola systems did not use the battery temp sensors. It was the Lucas/Magneti Marelli systems that did.

Supposedly the Motorola systems were also temperature compensating, but this function was done within the regulator itself.

Biggest problem with the Motorola systems from my experience has been worn brushes, followed by poor connections between the alternator - regulator - key switch.
 
The light comes on with switch on, goes out after motor starts. But alt doesn't put out more than 12v. when read at battery and alt hot terminal, and the battery discharges. Suspect it's wired incorrectly, I haven't traced back to ignition switch yet. I haven't used it in years and suspect a worker has "fixed" it.
 
It will take you 10 min to check these things out... Good multimeter is all you need. If the alt is bad then I would certainly go with a Delco. I've done several of them... but I see no reason to throw away a good Motorolla if it's working. They are a very good alt. If you do end up converting, you need good wiring anyway so it doesn't hurt to check that. I usually just unhook the reg and tape up the field wire at the alt, then hook the large wire to the BAT connection, jumper terminal 2 onto the BAT terminal and hook the other outside wire on the alt to terminal 1... IIRC, the other wire on the back of your MOTO is a ground. Otherwise I don't alter the wiring harness on the tractor. You may or may not get away with the top mounting bracket you have... but you will probably need to modify the lower bracket to slide the Delco further ahead and you'll probably have to change the pulley's unless you score a delco with a 1/2" pulley.



I'm not going to debate with Bern about the existence of the battery sensor on this tractor. It's 15 years since I had one with that Moto alt and I thought the sensor was there but I could be mistaken. If it's not there, it's one less thing to check.

Rod
 
Thanks. I was under the impression that there was not a voltage regulator with this setup. I didn't see one. Would you know where its located? or what it looks like? Behind the instrument cluster maybe ?
 
Regulator should be on the panel just in front of
the fuel tank...just behind the battery. Roughly 3"
square, about 1/2" thick.
 

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