Voltage Regulator or Generator

[Larry Barnes]

Hi Guys!

My 8N died last Saturday while brush hogging. Found that the battery was drained to less than six volts and it quit in the field. I took the battery out and put it on the charger overnight. Then let it sat unhooked for 24 hours. Checked it again and it showed 7.0 volts all day, so I assume it's OK. Put it back in the tractor and started it. Measured the output from the generator and it said 8.0 volts. So I says to myself, "self, the charging system is working." So I started brush hogging again.

But sure enough, after I had done about the same three laps at full throttle, it died again. So my question is, do you think I need a new voltage regulator...and/or a new starter? Last night I took the battery in and recharged it again, I hope enough to drive the tractor into my shop so I can work on it.

So is a charging rate of 8 volts enough? Does the charging rate increase when you increase the throttle? And if so, isn't it the voltage regulator's job to do that?

While I suppose it would make financial sense to convert it to 12 volt If I've got to replace the regulator AND the generator. But six volts has worked fine. Till now.

I'll appreciate your thoughts. Now I'm gonna go bring it inside before it rains!

Larry in Ohio

 

[JMOR]

There may be more........................but for sure, the battery is a problem! A good fully charged battery, without a generator at all, should run the ignition for many hours. Just as an example, not knowing your specifics, 80A-H battery divided by maybe average ign current of ~1.5 amps= 50 hours.

 

[Jim L WA]

JMOR makes a good point about the health of your battery, but measure the voltage at the battery with the tractor running at different R.P.M.s., The 8 volts out of the generator may be getting lost.

 

[Larry Barnes]

There may be more........................but for sure, the battery is a problem! A good fully charged battery, without a generator at all, should run the ignition for many hours. Just as an example, not knowing your specifics, 80A-H battery divided by maybe average ign current of ~1.5 amps= 50 hours.

You may right. I confess to adding near a half gallon of distilled water to it this morning. How do I test a 6 volt battery that shows it has 7.0 volts? But another thing I noticed is that the tractor's round volt meter on the dash was showing a discharge instead of a charge while I was driving it in to the barn. But maybe that was because I had just taken it off the charger?

 

[Larry Barnes]

JMOR makes a good point about the health of your battery, but measure the voltage at the battery with the tractor running at different R.P.M.s., The 8 volts out of the generator may be getting lost.

When I increased the throttle by half a bit, it just stayed at eight volts. Didn't try it at high RPM though.

 

[JMOR]

You measure battery voltage with a few hundred amperes of load on it.

 

[Larry Barnes]

You measure battery voltage with a few hundred amperes of load on it.

So if it shows 8 volts while running at half-throttle, that's good, right? But if I'm really running it hard under stress, could the battery not be able to keep up? I'm gonna see what I can find out about testing a battery under stress...

 

[Jim.ME]

So if it shows 8 volts while running at half-throttle, that's good, right? But if I'm really running it hard under stress, could the battery not be able to keep up? I'm gonna see what I can find out about testing a battery under stress...

Under stress when running? I don't see the battery being "under stress" once the engine is running (whether charging or not) unless you are powering several banks of stadium lights or such. JMOR's post (#2) should sum up the "stress" the battery is under if it is only powering the ignition. The amount of electrical power the ignition requires to run the engine at full throttle under load, isn't going to change much from electrical power required at idle.

As JMOR suggest in post 6, you need to have the battery tested with a good load tester which can load it with several hundred amps draw. When you tested it with it running and got 8 volts where did you do the test?

The battery hasn't been discharged and charged backwards, has it? When you check it with a voltmeter is the red lead (+) on the + post and the negative lead (-) on the - terminal? Is the tractor still positive ground as it was originally?

 

[Btzj02]

Assuming you have proved the battery good: After running the tractor for a few minutes I would suggest measuring the voltages at the generator and at the 3 voltage regulator terminal screws at different RPMs. Measuring at both the Generator and the GEN terminal screw would rule out any issues between the two points. If the generator is healthy and there is an open circuit between the GEN terminal screw and the BAT terminal screw the GEN voltage would increase with engine RPM and the BAT voltage would not change and simply read the battery voltage. If the Gen screw voltage is measuring a lot higher than the Bat screw voltage I would begin to suspect the regulator is bad. Back when I was trouble shooting a bad regulator I found that hitting the Voltage Regulator cover with a wrench would cause it to work again. That only lasted a week or two before even that would not work and I replaced the Regulator.

 

[Larry Barnes]

Assuming you have proved the battery good: After running the tractor for a few minutes I would suggest measuring the voltages at the generator and at the 3 voltage regulator terminal screws at different RPMs. Measuring at both the Generator and the GEN terminal screw would rule out any issues between the two points. If the generator is healthy and there is an open circuit between the GEN terminal screw and the BAT terminal screw the GEN voltage would increase with engine RPM and the BAT voltage would not change and simply read the battery voltage. If the Gen screw voltage is measuring a lot higher than the Bat screw voltage I would begin to suspect the regulator is bad. Back when I was trouble shooting a bad regulator I found that hitting the Voltage Regulator cover with a wrench would cause it to work again. That only lasted a week or two before even that would not work and I replaced the Regulator.

Thanks. I'll go down and do that. And I am going to take it to a Battery Shop to have it "load tested" today.

 

[Eman85]

I noticed is that the tractor's round volt meter on the dash was showing a discharge instead of a charge while I was driving it in to the barn.

Voltmeter or ammeter?

 

[Jim L WA]

Larry, you are putting the battery back in as positive ground, right?

 

[Larry Barnes]

Hi Guys! Success! I had an old 8N voltage regulator that a friend gave me when he had switched is tractor to 12 volt years ago. Funny, the date stamped on the part was 1949. (My birth year). It took me about a full day and a lot of sore fingers to get mine off and his on. Thought I'd have to take the hood off, but "only" had to move the air cleaner. And I cursed that they held the old regulator on with flat head bolts! But it started right up and produced a steady voltage flow at idle and went up to eight volts at half throttle. I still can't believe that a rusty 75 year old voltage regulator works as good as a new one. Spent the whole day yesterday brush hogging the horse pasture. Life is good!

Thanks for your help.

Larry