JD LA generator output question

I have the hood off my LA to change the head gasket. I now have easy access to generator and cutout relay. All wiring currently removed from tractor. With tractor running should I get around 6v from the F terminal on Genny? I am getting 0.4V. cutout relay is staying open. I do have Johns very detailed troubleshooting guide, but it assumes everything is hooked up.

If I ground the switch and hook everything up as if the hood is will things work as they should assuming genny is good?

It is so much easier working on the genny with the hood off, that is why I ask. Everything was working fine couple years ago and all of a sudden the genny stopped working. Using John's check list I could not find the problem. I am hoping there is an easy way out by simply checking genny at the F post.

Thanks




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Generator motor test is simple and indicates the basic condition of the generator unit alone. Fan belt off, the wire off the A terminal. use a jumper to put battery voltage to the A terminal. (make sure the other battery terminal is grounded to the chassis. The generator should take off and spin rather nicely. Do this for just 20 seconds or so. Next use a screw driver or jumper to prepare to ground the F terminal. Now run the motor test again and ground the F terminal while it is motoring. The generator should slow down rather obviously with it grounded, then speed up when you remove the ground. Limit your motoring to about one minute. If it does as I describe it is likely good. If not, it needs service. Jim

Why is that field terminal connected to nothing?

Thanks. I will give that a try. Sounds simple enough.

I removed all the wiring when I took the
hood off. It does have a wire that
connects to it.

The Motor Test described in my Troubleshooting Procedure can show if the genny itself is okay, if it passes BOTH tests it should be okay.....

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.

Your question With tractor running should I get around 6v from the F terminal on Genny?

The gennys output is on the ARM post and frame/ground NOT the FLD. If running but the FLD isnt connected to where it gets a ground (such as Low High charge light switch or a VR) the residual magnetism in the iron field poles will still yield some output (across Arm & Ground) but the FLD needs a ground for charging purposes.

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 isnt well grounded.

b) IF ITS 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 isnt 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 dont 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 isnt 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 dont charge, you're left with a bad battery or wiring or the Gen itself.

John T

Thank you for the info. I got some voltage out of it tonight. I hooked the battery to it and it did just what you said. So I removed Genny and sanded down the bracket that it attaches to in case it was not grounded well. I am only getting Voltage at about half throttle and up, nothing at idle. Also my multimeter is reading in the low to mid teens. Is that too high for a 6v system? The voltage was jumping quite a bit but that was probably because I was just holding meter loosely against terminal, not a tight connection.