Farmall A electrical issue

Howdy,

Got a farmall A in the shop with an electrical issue. The tractor is 6 volt, positive ground. Not sure what is wrong with it though. The generator and voltage regulator were taken to a shop and checked out okay. When the tractor is not running and the switch is on the third position the lights come on and it shows discharge. In the other two positions there is no change with the ammeter or lights. When running, there is no movement in the ammeter on the first and second positions of the switch but it swings to the discharge at around 15amps when in the third position with the lights on.

I checked the battery and it shows 6.4 volts when the tractor is both running and not running. I have polarized the generator. I am wondering about the switch as to whether it is correct for this tractor. It is a replacement switch and here is what it has on it. At the top there looks to be a resistor with no connections. Below it is a terminal marked F. Below that is a silver box with two connections on it and it is marked Bat. To the side is a connection marked L.

The tractor is wired as follows:

F terminal on generator to F terminal on voltage regulator. A terminal on generator to GEN terminal on voltage regulator. BAT terminal on voltage regulator to BAT terminal on switch. Second post on BAT switch terminal to ammeter. L post on voltage regulator to F terminal on switch. Second post on ammeter to starter.



I also checked my connections with the ammeter with the tractor off. I get 6.4 volts at all posts (except L on the switch and the F on voltage regulator).

I am wondering if the voltage regulator and switch may be incorrect for this tractor. Any assistance in solving this mystery would be greatly appreciated. Thanks in advance and God bless.

--old fashioned farmer

first.. lets see if the generator is doing anything.

lets do a motor test.

pull wires off genny, slip belt off...... jump battery hot to armature.. jump field to case of genny... she should spin

if she does spin:

with her running.. what doe the armature show at mid throttle?

what does she show when you ground the feild again?

Okay you said the generator and regulator have been check out and is good. Do you have a voltage regulator or just a cutout relay????

The wire on the L terminal of the regulator is not needed. That is for an idiot light. Remove that wire and recycle it.

If you have a discharge with lights on and engine off this is normal. With engine on you should have charge then if you turn the lights on with engine running the charge rate will decrease. Be sure to check the fluid level in your battery and one most more importantly check the belt tension on the generator. These generators don't put out many amps when regulated, maybe 20 at the most. The engine must be revved up for the generator to charge. This is why many switch to alternators, they charge at a much lower RPM. If you have a generator and work your tractor like plowing or other field work engine RPMS would be high and the battery would stay charged but few people actually use these old tractors for their original intended use.

A good 6 volt battery should read around 6.3 volts when setting but when coupled to a good working charging system with the tractor at fast RPM the battery voltage should rise to at least 6.5 up to 7+.........

If your what you call Voltage Regulator has 4 terminals (BAT GEN FLD LOAD) its indeed a full fledged Voltage Regulator and NOT a Cutout Relay. That system did NOT use the LowHighDimBright (LHDB) light switch for charge control like the Cutout Relay system used, the VR automatically regulated charge. With the regular lights only light switch (as used with a VR) there would be no connection from FLD on the genny up to FLD on the LHDB switch, the gennys FLD wires ONLY to the VR.

Correct wiring with a 4 terminal VR would be:

BAT to Load (NOT battery/starter) side of ammeter
GEN to gennys ARM post
FLD to gennys FLD post
LOAD feeds hot battery voltage up to loads like
lights and Ignition
Again, NO wire from FLD on Genny up to any light (LHDB) switch

Once you get that figured out heres a procedure to determine (Para 5) if non charging is a genny verus VR or some other problem and in Para 8 how to Motor test a genny

TROUBLESHOOTING CHARGING SYSTEMS

ARE YOU SURE THE AMMETER IS WIRED CORRECT AND WORKS????? If you turn the lights or ignition on (if coil ignition not a mag) when she’s not running, the ammeter should swing over to the - discharge direction, does yours??? Are BOTH the ammeter terminals reading hot battery voltage?? They MUST !!!!!!! There’s but one wire on the ammeters Supply (from battery/starter) terminal while its other Load terminal wires to the BAT terminal on a Cutout relay or VR PLUS wires to feed loads like lights or ignition, unless where a 4 terminal VR is used where lights n ignition are fed from the LOAD terminal on the VR.

To Polarize the Generator, first temporarily dead ground the Gens Field post to case/frame, then momentarily flash jump a wire from the Cutout Relay or VR's "BAT" terminal over to its GEN (or ARM) terminal and you ought to get a small spark. Same things accomplished by momentarily flash jumping a hot wire (BAT terminal on Cutout Relay or VR or starter post etc) direct to the Gens ARM post to get the spark.

TROUBLESHOOTING A CHARGING PROBLEM IN CLASS A DELCO TYPE SYSTEMS

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,,,,,,,,,,to and through the Cutout Relay (between its GEN and BAT terminals, regardless if on a VR or Relay),,,,,,,,,up to the Load (NOT to battery) side of the Ammeter,,,,,,,,,to and through the Ammeter,,,,,,,,,,from BAT side of Ammeter to ungrounded battery terminal, often via the starter lug post. Is yours wired that way or equivalent ??? The ammeter 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 and/or the lights glow brighter (half that on 6 volt systems). Have you tried that in case the ammeter isn’t working right?????

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

3) The Gen to VR (if it has one) 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 ignition.

WIRING ON CUTOUT RELAYS: They wire BAT side to ammeters Load terminal,,,,,,GEN side to gens Armature post. On cutout relay systems, the Gens Field post is wired to the light switch where it gets a dead ground for high charge or a resistive ground for low charge. Therefore, there must be a good connection from the Gens Field post up to the switch PLUS the switch is good and it’s well grounded !!!!!!!!

4. THE GEN AND VR OR CUTOUT RELAY 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 see what happens????????????????????????????

NOW, if the Gen and VR are grounded,,,,,all is wired correct,,,,,,,,BAT terminal on VR or Cutout Relay 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 the battery checks okay, 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 OR CUTOUT RELAY PROBLEM

5. a) VOLTAGE REGULATOR SYSTEM: With the tractor running, temporarily ground the Gens Field post to case. If she charges then but NOT otherwise, the VR may be bad, or a wires missing from VR's Field post to the Field terminal on the VR, or the VR isn’t well grounded.

b) IF IT’S A CUTOUT RELAY SYSTEM and she charges only if you dead ground the Field but NOT otherwise, its either a bad switch or the switch isn’t well grounded or else the wires bad or open from the Gens Field post up to the switch. INSURE THAT GOOD SWITCH GROUND AND WIRING

6. If she still don’t charge, leave the Field grounded and jump a wire across from the VR or Cutout Relays BAT terminal over to its GEN terminal (jump by passes the cutout relay) and see if she charges. If then but not otherwise, a VR's cutout relay isn’t working correct (maybe points burned/carboned) or a Cutout Relays NOT working or not wired correct.

7. With the 2 steps above, you have basically by passed the VR or Cutout relays functions, so if she still don’t 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 and have the Field Post dead grounded to frame, it should motor n run well (Armature n Brushes and Commutator likely okay). Then, if you next remove the Fields ground and it speeds up some, the Fields probably good. If it passes both those tests, it should charge, and if not, it may be a wiring or battery or grounding problem. The hot battery voltage may be taken off the VR's BAT terminal or the starter post or the battery itself for this test.

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 and they cant be worn down too low.

SUMMARY: Check the wiring,,,,,the grounds,,,,,,insure BAT on VR or Relay 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 (half that for 6 volt system) 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 the Gen and VR or relay are okay.

Good Luck n God Bless, let us all know.

John T

Your statement: "The wire on the L terminal of the regulator is not needed. That is for an idiot light. Remove that wire and recycle it. "

John, FYI On Farmalls (Deere and others also) that used a 4 terminal (BAT FLD GEN LOAD) Voltage Regulator the L terminal is used to feed hot battery voltage up to LOADS like lights and ignition.

With only a 3 terminal (BAT FLD GEN) VR having no LOAD terminal, loads were fed instead off the Load (NOT battery/starter) side of the ammeter.

Hope this helps, post back any questions, best wishes n God Bless

John T

Thanks John.

Got a feeling wiring at the switch may be the issue so will re-wire per your instructions. Then will go through the rest. I appreciate the help. Electrical work is not really my thing but I would love to learn as much as I can for future reference. I don't like to give up because I don't know something. I can always learn new. God bless.

--old fashioned farmer

Yep its a huge diffrence if you have a Cutout Relay and LHDB switch versus a Voltage Regulator and a regular light switch. With the relay the gennys FLD post wires to the LHDB switch for charge control while with a VR and regular light switch (NOT for charge control) gennys FLD wire to FLD on VR NOT to light switch

John T

Howdy,

Well, got the problem figured out but in a way I don't usually like to do...by accident. I did a check on my wiring and got it straight. After that I started through your checklist and kept coming up empty. I was on the portion checking the regulator when I got a wire bumped against another and got a good spark and my ammeter showed a constant discharge. I figured I had fried something but it turned out good. I popped the top off my voltage regulator to see corrosion inside on the points. I decided to recheck the regulator with the ground at F terminal test and low and behold the ammeter showed charge. So, my issue was in the regulator. I can't say why it never showed before as I had done the tests a day or so ago. Anyway, I decided to replace the voltage regulator. Now on to the carburetor. Thanks again John! God bless.

--old fashioned farmer