Generator charge circuit troubleshooting

   / Generator charge circuit troubleshooting #1  

BobReeves

Platinum Member
Joined
Aug 9, 2003
Messages
502
Location
Tulsa OK
Tractor
Ford 3000
Finally finished the hydraulics overhaul on my Ford 3000 this morning. Had a little trouble getting it started, replaced the fuel filter but the book didn't tell me I also needed to bleed the injector pump. All it said was to bleed the filter, hard lesson. In any case I had a battery charger connected to it when it started, not sure if the charger had anything to with it or not but now the generator light stays on.

The IT manual is pretty much worthless except it does have a wiring diagram. I haven't worked on a generator charging circuit since the early 60's and am pretty much at a loss as to how to trouble shoot the charging circuit. Have a good meter and am pretty good with electrical stuff but don't want to jump in blindly and mess something up that may not be broke.

Can someone run through a basic troubleshooting procedure for a generator charging circuit? Like can I just stick 12 volts on the field to see if the generator is working without smoking anything? How does one determine if the regulator is working?

thanks
Bob
 
   / Generator charge circuit troubleshooting
  • Thread Starter
#2  
Looks like it may be the regulator. Just started it again and had 13.0 volts at the battery and milivolts on the field. Will have to pull the hood off to get good access to the regulator but am I headed the right direction?
 
   / Generator charge circuit troubleshooting #3  
Keep in mind that a nice new GM one wire alternator is only like 50$. With new regulator, bearings, etc.

When my IH dozer was charging at 18 volts (can you hear the battery boiling?) I just did the quick and easy GM 1-wire instead of repairing and troubleshooting the old system. It turned out very well in that case.
 
   / Generator charge circuit troubleshooting #4  
</font><font color="blue" class="small">( Looks like it may be the regulator. Just started it again and had 13.0 volts at the battery and milivolts on the field. Will have to pull the hood off to get good access to the regulator but am I headed the right direction? )</font>

I'd say so. But unless you find a simple mechanical
problem such as a bad connection it would probably
be easier to swap the alternator with an automotive unit
of similar footprint. Doing so you will likely increase
your charging system's ampacity as well.
 
   / Generator charge circuit troubleshooting #5  
Presumably you have a unit that outputs DC directly. I have a JD 4100 that outputs AC to a rectifier/regulator which complicates matters. I posted a similar thread here - may want to read. At this point, it seems my whole problem was poor connections. A VM attached to the battery w/engine on now reads 12.5-14. I traced all the wires from alternator to battery. Alternator was delivering 20-50v (low-high rpm) AC. I found many dirty connections. There were also protection relay's and diodes. They all seem to be OK, but presumably somewhere in the path I had bad connections, as I could never keep a charge on the battery. Now I appear to be OK.. with >12V DC and amps flowing on the battery cable when I run it.
 
   / Generator charge circuit troubleshooting
  • Thread Starter
#6  
Opened up the regulator and wow what a mess of corrosion and burnt contacts. NH says $35.00 for a new one and have 4 in stock, will probably go that route after I make sure the generator is OK. Still wondering if I can stick 12 volts on the field wire to test the gens output?

Wouldn't mind upgrading it to an alternator and the additional power would be welcome but don't want to loose my tach and hour meter which runs off the back of the generator. Afraid it would end up a can of worms with a special aftermarket alternator. The generator does fine when it's working.
 
   / Generator charge circuit troubleshooting #7  
</font><font color="blue" class="small">( Opened up the regulator and wow what a mess of corrosion and burnt contacts. NH says $35.00 for a new one and have 4 in stock, will probably go that route after I make sure the generator is OK. Still wondering if I can stick 12 volts on the field wire to test the gens output?)</font>

IIRC energizing the field winding directly with 12V you will get
a much higher output voltage from the generator. So if you
do so make sure the output of the generator isn't feeding back to
the battery/electrical system.

</font><font color="blue" class="small">(
Wouldn't mind upgrading it to an alternator and the additional power would be welcome but don't want to loose my tach and hour meter which runs off the back of the generator. Afraid it would end up a can of worms with a special aftermarket alternator. The generator does fine when it's working. )</font>

Ah, ok. Didn't realize there were other dependencies. At $35 for a
new regulator that isn't too bad. Contrast that with a new 40AMP
alternator in my L48 weighs in over $600 -- HA!
 
   / Generator charge circuit troubleshooting
  • Thread Starter
#8  
Thanks for the help, found this in an old thread on Yesterdays tractors, sorry didn't get the posters name. Think it was quoted from the Ford service manual. Sounds like a safe way to check the generator...
**************************
Disconnect the two wires from the terminals on the generator noting which went where.

Jumper the two terminals.

Connect a 20V DC volt meter to one of the terminals and the black/common lead to ground.

Crank the tractor and run at ****IDLE SPEED****

note the voltage reading.

Slowly increase the engine RPMs

The generator voltage should rise smoothly and rapidly with RPM's.

Do not allow the voltage to exceed 20V's and do not run the tractor for long wired like this. If the voltage rose smoothly and rapidly above 15 volts and holds steady at the same RPM's then the generator is working most likely.
 
   / Generator charge circuit troubleshooting #9  
</font><font color="blue" class="small">( Disconnect the two wires from the terminals on the generator noting which went where.

Jumper the two terminals. )</font>

Hmm. Looks like this is expecting residual magnetism
in the stator/field to self-excite the generator and drive
the field at a reduced voltage. If this shouldn't work (ie:
no voltage output from the generator) you can remove
the jumper and try to drive the field at a low voltage with
the engine at idle. An adjustable DC power supply would
be ideal here but if you can find a dash dimmer switch and
a 12V battery that would work as well. Make sure you have
2V or less going into the field before the rotor is in motion.
If you can't get the voltage across the field down low enough
try adding a light bulb as a dummy load in parallel with the
field winding.

You can increase engine speed and/or field voltage+current
to verify this causes a corresponding increase in generator
output voltage.
 
   / Generator charge circuit troubleshooting
  • Thread Starter
#10  
Generator passed the test, off to NH to pick up a regulator. While I was at it cleaned all the conectors so as soon as I get back with the regulator it should be good to go.

Thanks,
Bob
 
 
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