voltage testing six volt generator

[drdave]

What is the best way to differentially diagnose the voltage reg. from the generator using a voltage ohm meter?

 

[souNdguy]

Read your manual.

Do a genny motor test... this tells you if the genny is likely good.

You can then try full field tests and use some jumper wires, and look at your ammeter and decide if it is genny or regulator..

First what you have to tell us is WHAT TRACTOR you are working on.. cuz the A-circuit and B-circuit diagnostic techniques are different.

Soundguy

 

[drdave]

It's an 8N, 1947. The genny has three wires and a high/low adjustment screw. Arm is on the back plate and the field and ground are on the side.

 

[souNdguy]

Adjust 3rd brush all the way .. jumper bat to armature.. and make sure case is grounded... do a motor test as in the fo-4 manual.. report back.

soundguy

 

[drdave]

Okay, I went home and did what you suggested last night, and the genny does motor. I looked at the VR and it seems clean, not burnt or welded shut but I will replace it anyway because its relatively inexpensive. I noticed when it motored it spun in the opposite direction of what it would with the engine running which makes sense to me. Buuut....the ammeter still does not show a charge even when I open and close the contacts in the VR. also when using the VOM I can't seem to find a current when I put the probes on the arm, field or grnd posts in any combination. How do I use the VOM to see if it's charging? Oh, the ammeter is the induction type and it does indicate discharge when I start it so I surmise (not assume, you know what that does)it is working.

 

[JMOR]

(quoted from post at 10:58:21 02/22/08) Okay, I went home and did what you suggested last night, and the genny does motor. I looked at the VR and it seems clean, not burnt or welded shut but I will replace it anyway because its relatively inexpensive. I noticed when it motored it spun in the opposite direction of what it would with the engine running which makes sense to me. Buuut....the ammeter still does not show a charge even when I open and close the contacts in the VR. also when using the VOM I can't seem to find a current when I put the probes on the arm, field or grnd posts in any combination. How do I use the VOM to see if it's charging? Oh, the ammeter is the induction type and it does indicate discharge when I start it so I surmise (not assume, you know what that does)it is working.

Well, I'll be interested to see SouNdguy's response to you, but in the mean time, you say, "I noticed when it motored it spun in the opposite direction of what it would with the engine running which makes sense to me.".

That doesn't make sense to me.

When you did the motor test, did you connect a jumper from FIELD to case ground at same time you connected the ARMATURE to the battery? If you did have the FIELD grounded, did it make any difference in motoring speed, etc. whether Field was grounded or not?

About the only way I can see reverse rotation would be if the gen was last polarized opposite of the way you are now motoring it AND that you are now leaving the FIELD disconnected and motoring on residual magnetism only.

 

[souNdguy]

You would measure power across armature and ground.

If the unit motors.. it should charge.

throw the belt back on but don't hookup the field and arm wires... start engine.. check from arm to grnd with a meter.. if no reading on a digital, use a test lamp... if lamp lights.. hook armature to bat contact on vr.. see if meter registers a charge.. if so, your vr cutout is bad.

you can try hooking the field up at that point to.. genny field control may still be functioning.. etc..

soundguy

 

[drdave]

JMOR, thanks for the reply, I did not have the field grounded and when I did the motor test all I did wasrun a jumper from the battery post on the positive side to the arm contact on the genny......oh, I think I answered my own question, I must have reversed the gennies polarity then, ok so how do I unreverse it?