New voltage regulator bad?

fourswild

New User
This is a sequel to my problem with getting my generator to charge the battery on my MF 65.

After determining the old VR cutout relay (A to B) was bad, I obtained a new VR and tested it:

induce 12v to A, hear relay click, read 12v on B and L;
induce 12v to B or L, silence, read Zero v on A.

installed VR, checking grounds and that each terminal reads correctly as wires installed. When complete, prior to polarizing generator in preparation for start, terminals B and L read hot, A and F not, and ammeter is neutral.

Polarized generator: ground F, jump A to B, heard click and got spark. Ammeter reads full discharge -30A
Disconnect neg batt cable, when reconnected ammeter reads neutral.

Start tractor, as it comes up to speed ammeter reads -20A, tried accelerating to 1800 rpm, no change.
Shut down, switch off, ammeter reads -30A, until neg cable removed.

Am I far off in thinking that one of the relays in the VR is a reverse current cutout and that it should be opening when the generator isn't turning? If so, what makes it open when it should?

Any other ideas on what would be causing this discharge?
 
1. I don't know why you were mucking around "testing" a new VR "out of circuit"?

2. The cutout relay points should NOT have closed @ "12 Volts", or when you polarized it without it running

Typically, they don't close until the generator is outpointing closer to 13 Volts.

3. Since the cutout opens when the generator stops putting out more voltage than the battery, and current flow reverses.

If the generator is defective, AND the cutout points closed and never opened when you polarized the generator, since they closed at too low of a voltage, and there never was a current reversal because the generator never charged, the points are gonna remain closed.
 

I'm not quite sure what to make of your reply. It sounds like you are saying the new VR is defective because the points never should have closed either at polarizing or running (if gen is defective), but since they did, they wouldn't re-open because there wasn't a reverse flow. But what closed them initially?

Isn't the flow from the battery to the generator a reverse flow when the engine shuts down? Can the relay coils be operated by flow from either direction?

Doesn't the ammeter showing -20a when running vs -30a when stopped indicate some output from the generator? (I've done several other tests that indicate the generator is putting out current)

Sorry for so many questions, I appreciate your help
 

"Can the relay coils be operated by flow from either direction?"

Yes, in a typical mechanical cutout or regulator, the cutout relay closes at a pre-set voltage, of either polarity.

It is the REVERSAL of current flow (and the resulting magnetic field reversal) in the series winding that helps "kick it out" when the generator stops charging, and DRAWS current.

I am traveling and can't type up a more long-winded reply at the moment.

Hopefully GURUS JohnT or JMOR will chime in.

In the mean time, here's some reading material...

http://www.cleancomputes.com/Cub/Blue Ribbon Service Manuals/GSS-1310 Electrical/Page-01.jpg
 
Bob; The reverse current creates a magnetic field that is opposite the pull-in field. They tend to cancel each other. The spring opens the points. A magnetic field always attracts unless it is from another magnet. Then like poles repel. If the points stick and the generator is stopped, the reverse flow will pull the points tight together again. He may have messed up the points or the pull-in windings with his 'testing'.
 
I'm late getting here, just returned from our local tractor show. I'm unsure if applying all those "test voltages" on a new VR may have messed it up. I will just lay some theory on you and maybe you can figure things out.

Normally the Cutout Relay between the BAT and GEN/ARM terminals should be open UNTIL voltage with respect to ground on ARM slightly exceeds that of BAT to ground at which time it latches in so the genny can charge the battery. When you shut down and ARM voltage drops the relay should open otherwise the battery would reverse discharge quickly and the ammeter would indicate a high discharge rate.

If your ammeter (assuming its wired correct??) swings over to a high - discharge with the tractor not running, the cutout relays points are stuck together or something is wired wrong or theres another problem I haven't yet considered.

Is your new VR suitable for your ground, Pos or Neg??? Did you polarize the genny before start up as incorrect genny polarity can damage a VR??

A good VR just sitting there on the bench should read an open circuit from BAT to case ground and an open circuit from BAT to GEN/ARM since the cutout relay is open. FLD to ground should be very low ohms and GEN/ARM to ground may be like 20 to 50 ohms (sorry no exact specs, that's a guess) as that's the cutout relays shunt winding.

If your BAT to GEN/ARM is a closed circuit the cutout relay is stuck closed.

Most VR's that are 4 terminal with a LOAD terminal has the GEN/ARM terminal underneath or off on one side by itself.

Darn if I know whats wrong not being there

My Troubleshooting procedure can diagnose if non charging is the fault of the genny or the VR.

John T
John Ts Troubleshooting
 
"Normally the Cutout Relay between the BAT and GEN/ARM terminals should be open UNTIL [b:d79000eab5]voltage with respect to ground on ARM slightly exceeds that of BAT to ground[/b:d79000eab5] at which time it latches in so the genny can charge the battery. "

Pretty close & perhaps just wording, but.........VR doesn't care what battery voltage is when cut out closes. That is a designed in pre-set voltage in the cut out itself.
 
I think we basically agree on the operation and theory, perhaps just wording as you noted. The voltage on ARM (even though its a pre set level, say 13 + or -) is normally a voltage that slightly exceeds battery voltage of 12.6, before it latches in. I just wanted to avoid assigning any EXACT voltage to when the relay latched in so I said "slightly exceeds that of BAT...." which it probably is assuming all is good and working. I agree with you in that it don't care about battery voltage as when it reaches say 13 volts it latches (which hopefully slightly exceeds a good batterys 12.6 volts)

When I get in a hurry I don't think out in exact great detail and carefully choose my words as I should MY BAD LOL but hey I answer a ton of questions and try my best to help.

As always fun sparky chattin with you.

John T
 
I never really doubted that YOU knew. :) Comments were primarily for the readers, many of which likely do not know.
 
Yep there"s a lot of this stuff we muddle through probably wrongfully assuming the reader knows a certain amount which he may or may not. I"m long winded and wordy enough as is let alone even more detail in my answers lol. Being an old engineer and technical and spec writer coupled with this attorney thing makes it hard for me to keep it short n simple sometimes, yet other times I"m in a hurry (when I may get in trouble with the correct police lol).

PS as you know (but for sake of readers) its the Cutout Relays SHUNT WINDING TO GROUND that initially is conducting current that senses when its time to latch in (when enough current creates sufficient magnetic field), afterwhich the bigger gauge less resistance series winding is also in the circuit. Then when the tractors is shut down temporary reverse discharge current helps the relay un latch......That"s my understanding at least......

Fun yakkin with ya

John T
 
The reverse current"s magnetic field cancels the shunt"s field and the spring opens the contacts. If the contacts stick, the reverse current will pull the contacts tight together again. (bummer)!
 

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