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NAA ampmeter question???

M

Muskellunge

Member
Hello,

I just installed a new 6v batt in my NAA because the old batt tested bad. I polarized the gen by wiring the field to batt momentarily on the volt regulator.... getting a spark. I start her up and she starts strong and runs fine.

I noticed when she's running the amp meter is practically pegged at 30 on the the positive side. When I shut her off, the amp meter goes back to zero.

Is this correct? If not, what could the issue be?

Thanks all,

Muskie
 
Charge the battery fully and try it again.
The generator may just be playing catch up.
Definitely not normal if it stays that way.
 
(quoted from post at 21:04:47 08/26/16) Hello,

I just installed a new 6v batt in my NAA because the old batt tested bad. I polarized the gen by wiring the field to batt momentarily on the volt regulator.... getting a spark. I start her up and she starts strong and runs fine.

I noticed when she's running the amp meter is practically pegged at 30 on the the positive side. When I shut her off, the amp meter goes back to zero.

Is this correct? If not, what could the issue be?

Thanks all,

Muskie
Click to expand...
ou said battery to field. With all wires connected as normal or some other arrangement?
 
Yes, JMOR, Batt to Fld... Just a quick touch with a wire. All others wires appear to be hooked up correctly. I haven't messed with the wires for years.

Although, the gen wires look in poor shape. I ordered a new harness so I plan to replace wires. I'm concerned this pegging ampmeter may indicate something else.... I just don't know what???

Muskie
.
 
(quoted from post at 22:45:44 08/26/16) Yes, JMOR, Batt to Fld... Just a quick touch with a wire. All others wires appear to be hooked up correctly. I haven't messed with the wires for years.

Although, the gen wires look in poor shape. I ordered a new harness so I plan to replace wires. I'm concerned this pegging ampmeter may indicate something else.... I just don't know what???

Muskie
.
Click to expand...
ell, here is what. That was wrong polarization procedure. By doing that you placed a very high armature current thru the VR field contacts (about 15X normal) and welded them closed. Now with those permanently closed, the generator outputs to its full capability 100% of the time. If you are lucky, you may salvage the VR by removing cover , prying open the VR contacts & polishing them. Battery disconnected of course.
Next time follow the "B"-circuit (internally grounded) polarization procedure.
 
(reply to post at 20:00:51 08/26/16) [/

DOH! I did the "A" method for sure.

What you say about welded contacts makes sense because the amp meter is pegged.

Guess I'll have to pull the reg and see if I can get it open. Hmmmmm... Or maybe I'll just replace it.... There is a TSC nearby.

Thanks for the info, JMOR... I appreciate it.

Muskie
Click to expand...
 
I glanced right over the polarizing method, glad JMOR caught it!
If you go to TSC keep your receipt. Maybe they'll take it back.
 

Hmmmm.... Looking at my gen, there are 3 wires. One goes to a ground screw on the v-reg. Wouldn't this make it an "externally grounded" gen, thus use the "A" method to polarize?

Muskie.
 
(quoted from post at 23:48:02 08/26/16)
Hmmmm.... Looking at my gen, there are 3 wires. One goes to a ground screw on the v-reg. Wouldn't this make it an "externally grounded" gen, thus use the "A" method to polarize?

Muskie.
Click to expand...
o. the terminology has to do with whether the field coils inside the generator are internally grounded (thus externally supplied) "B-ckt", as your tractor was made, or externally grounded fields (internally supplied) "A-ckt", as 8Ns were made. Clear as mud, I'm sure, but that is the way it is.
In the B-ckt system, the VR feeds power to the field coils, whereas in the _-ckt, the fields receive power from inside generator and the VR provides a ground path for the fields.

Both A and B types have the case ground on the generator barrel.
 
Thanks again, JMOR!

I took the cover off the V-reg and both contacts are moving when I depress them.

Started it up and the amp meter still pegs +30 when giving half throttle or more.

I guess I'll have to replace the v reg, polarize correctly (B pic) and see what happens from there.

Muskie
 
(quoted from post at 12:33:37 08/27/16) Thanks again, JMOR!

I took the cover off the V-reg and both contacts are moving when I depress them.

Started it up and the amp meter still pegs +30 when giving half throttle or more.

I guess I'll have to replace the v reg, polarize correctly (B pic) and see what happens from there.

Muskie
Click to expand...
eave VT cover off, start engine & open the smaller set of contacts..........that should reduce the 30A charge.
 
I'll give that a try. We have a storm blowing through now(Michigan) so it will be in a bit.

So, if opening the smaller contacts does reduce charge..... This would indicate faulty reg?

Muskie
 
(quoted from post at 14:25:38 08/27/16) I'll give that a try. We have a storm blowing through now(Michigan) so it will be in a bit.

So, if opening the smaller contacts does reduce charge..... This would indicate faulty reg?

Muskie
Click to expand...
es. I see no other possibility if all wiring is correct.
 

Well, when I open the set at the bottom (near arm)with the tractor running, it drops the amp meter to 0'. If I open the top set (near Fld) when the tractor is not running the amp gauge drops to -30.

This sounds like a bad V reg?

Thanks,

Muskie
 
Muskie, what part of Michigan are you in?
If you're close to me (Ionia County) I might have a VReg.
 
(quoted from post at 19:27:24 08/27/16)
Well, when I open the set at the bottom (near arm)with the tractor running, it drops the amp meter to 0'. If I open the top set (near Fld) when the tractor is not running the amp gauge drops to -30.

This sounds like a bad V reg?

Thanks,

Muskie
Click to expand...
do not understand what you are trying to tell me. The two sets of contacts are identifiable by the cut out contacts being large and robust AND being normally open. The field contacts by being smaller & more delicate AND being normally closed.
With all turned off, you need finger pressure to close the cut out contacts and finger pressure to open the field contacts. Please re-state your previous description in terms of field contacts and cut out contacts. Thanks.
 
OK... So it goes like this:

Tractor not running, top set open, bottom set closed.

Tractor running.... Both sets closed

[i:3074152e4d]Well, when I open the set at the bottom (near arm)with the tractor running, it drops the amp meter to 0'. If I [b:3074152e4d]CLOSE[/b:3074152e4d] the top set (near Fld) when the tractor is not running the amp gauge drops to -30.[/i:3074152e4d]
 
(quoted from post at 11:39:48 08/28/16) OK... So it goes like this:

Tractor not running, top set open, bottom set closed.

Tractor running.... Both sets closed

[i:c2ee570507]Well, when I open the set at the bottom (near arm)with the tractor running, it drops the amp meter to 0'. If I [b:c2ee570507]CLOSE[/b:c2ee570507] the top set (near Fld) when the tractor is not running the amp gauge drops to -30.[/i:c2ee570507]
Click to expand...
hat tells me that it is wired correctly. That lower set should open or oscillate between open & close when battery is sufficiently charged to bring battery voltage up to around 14.5volts. That will then reduce the full charge amperes that you are seeing. Measure battery voltage while running (after running for several minutes at speed). If voltage is reaching about 14.5v & lower field contacts remain closed, then I say that field sensing portion of VR is bad.
 
(quoted from post at 12:10:02 08/28/16)
Yup... Thanks again for the time and info!

Muskie
Click to expand...
f charging won't bring battery voltage up near 7.25v, then it will continue to charge hard trying to bring it up. That is, with a good VR. If rising beyond 7.6v and still no reduction in charge current, then likely VR bad.
 

I srarted her up and the initial reading at batt was 7.2v. After several minutes it read 7.6v. This reading maintained. Never did the bottom (field) contacts open. They remained closed. The amp gauge was bouncing around between +10-+20.

Muskie.
 
39743.jpg

There we go with the pic.
 
(quoted from post at 13:07:32 08/28/16)
I srarted her up and the initial reading at batt was 7.2v. After several minutes it read 7.6v. This reading maintained. Never did the bottom (field) contacts open. They remained closed. The amp gauge was bouncing around between +10-+20.

Muskie.
Click to expand...
ell, it sounds like it was trying to function, since current came down from 30 to 'bouncing around 10-20'. Watch and see if it continues to raise battery voltage beyond 7.6v and if current continues to lower. The VR will not function exactly right without cover installed, because of temperature & even magnetic field will be somewhat altered by the presence.absence of cover.
 
I'll do that, JMORE. I have some mowing to do, so I'll install cover and keep my eye on amp meter. If it stays in the + 20 range, I'll replace the vr

Muskie
 
Keeping your receipt is often no longer always necessary (if you pay with a CC, which you should. The clerk can just look up your receipt and print out another
copy. Its all in a computer somewhere.
 
Update.... I installed cover on VR, mowed for a half hour or so, and VR finally came down. Appears to be functioning normally now.

Thanks for the help!

Muskie
 
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