Re: Farmall Cub Charging Issue

Posted by John T on May 15, 2017 at 10:09:48 from (216.249.81.101):

In Reply to: Farmall Cub Charging Issue posted by James Port on May 15, 2017 at 09:26:23:

I would first see if non charging is due to a voltage regulator problem versus the genny itself. If you take a jumper and ground the gennys FLD post and she charges then but NOT otherwise, the genny itself is okay so the VR is bad or its not well grounded. Try a jumper wire to ground the VR and see if that helps. Often a good cleaning of the gennys commutator and insure the brushes are held down good n tight and aren't worn down too low will help. Insure the genny and VR BOTH have good grounds and polarize the genny and try it again. If all fails see below

Heres my Non Charging Troubleshooting Procedure for Class A Charging Systems. In Para 5 it tells how to effectively by pass the Voltage Regulator functions to see if failure to charge is the fault of the genny versus the Voltage Regulator. It also has a Motor Test to test the genny.

If you havent polarized, you may wanna do that just to make sure!!!!!! Temporarily ground the Gens Field post to case then momentarily flash jump a wire from the VR"s BAT terminal over to its ARM (or GEN) terminal (or direct to ARM post on Gen) and you ought to get a spark. Always try the simple fixes first!!!!

1) For a good working Gen to get to and charge the battery, it has to have a path usually from the Gens ARM post output,,,,,,,,,,,To and through the cutout relay portion of the VR (between its ARM and BAT terminals),,,,,,,,,Up to the Load (NOT to battery) side of the Ammeter (if it has one),,,,,,,,,To and through the ammeter (if it has one),,,,,,,,,,From BAT side of ammeter to ungrounded battery post, often via the starter lug post. Is yours wired that way or equivalent ??? The ammeter (if it has one) should read hot battery voltage on BOTH terminals, does yours??? Even if an ammeter were stuck (but still continuous) as RPM increases the battery voltage should rise from 12.6 to near 14 volts (half that for 6 volt) and/or the lights glow brighter. Have you tried that in case the ammeter isnt working right???????

2) If the above is so, the BAT terminal on the VR MUST ALWAYS READ HOT BATTERY VOLTAGE. Does yours??? If not, the Gen cant get to and charge the battery.

3) The Gen to VR wiring is as follows:

BAT on VR to ammeters load (NOT battery) side

ARM (or GEN) on VR to Gens Armature post.

FLD on VR to Gens Field post.

(L) Load (if you have a 4 wire VR) up to BAT supply input terminal on switch to feed loads like lights and ingition.

4. THE GEN AND VR MUST BE WELL GROUNDED AND THE BELT GOOD N TIGHT. If any doubt, run a ground wire from the grounded battery post or clean solid frame member direct to the Gen and VR and see what happens?????????????????????????

NOW, if the Gen and VR are grounded,,,,,all is wired correct,,,,,,,,BAT terminal on VR is HOT,,,,,,,,Belt is tight,,,,,,,,,ammeter is good n continuous n works but she wont charge, have you had the batteries tested lately????? Is there electrolyte above all the plates and no cells have a gray or milky appearance?????? A bad battery may not accept a charge you know!!!!!!!! If she dont, proceed below to see if its a Gen or VR problem (AFTER you have insured the wiring per the above)

TO DETERMINE IF ITS A GEN OR VR PROBLEM

5. With the tractor running, temporarily ground the Gens Field post to case. If she charges then, the VR may be bad, or a wires missing from VR"s Field post to the Field terminal on the VR, or the VR isnt well grounded.

6. If she still dont charge, leave Field grounded and jump a wire across from the VR"s BAT and ARM terminals (jump by passes the cutout relay) and see if she charges. If then but not otherwise, the VR"s cutout relay isnt working correct (maybe points burned/carboned/resistive)

7. With the 2 steps above, you have basically by passed the VR functions, so if she still dont charge, you"re left with a bad battery or wiring or the Gen itself.

8. MOTOR TEST. You can Motor test the Gen. If its grounded and you remove the belt and apply hot battery voltage direct to its ARM Post, it should motor n run well (Armature n Brushes and Commutator okay). Then if you ground the Field and it slows down some, the Fileds probably good. If it passes both those tests, it should charge, and if not, it may be a wirign or battery or grounding problem.

9. Typical Gen problems may be the brushes are worn down or the hold down spring assemblies are stuck/corroded/dirty and arent pushing the brushes tight down against the commutator. Check those things out. Worse may be bad fields or armature etc. Air and WD 40 etc can clean and free them, the hold downs must be free n snap and hold the brushes DOWN TIGHT.

SUMMARY: Check the wiring,,,,,The Genny and VR grounds,,,,,,Insure BAT on VR is hot,,,,,,,check battery (maybe load tested and Specific Gravity checked),,,,,,,,,good tight belt,,,,,,,insure ammeter is continuous (BOTH sides HOT),,,,,,see if battery voltage rises above 12.6 (6.3 for 6 volt) and/or light glow brighter,,,,,,,,,do the Field and cutout relay VR by pass checks,,,,,,,,insure the Gens brushes arent worn down and the hold down springs are free n clean and push the brushes down tight,,,,,,,,,,,check the connections,,,,,,,,,try the Gen Motor Test to see if its good.

You may just have a bad battery or bad ground or connection if you say the Gen and VR are okay.

Good Luck n God Bless, let us all know.

John T

• John T's Charging Troubleshooting

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