Generator Check

[strausbo 2]

I have a K181 with a starter generator on it. I have it installed in a B-80 tractor. It starts nice and runs well. I used an old wheel horse ammeter in my setup to monitor the generator. My question is this: When the engine is running, I do not see any needle movement on the ammeter. It stays on zero. I have no way (yet) to apply a load to see if it will change. Should the ammeter show a slight charge when the engine is running (needle slightly off zero toward the plus side)? How can I check the ammeter to verify that it is working? I want to verify that the generator is working. Any other help/suggestions would be appreciated. Thanks in advance.

strausbo

[W9JAB 156]

You could load it with a blow dryer or heat

gun across the batt. you should see that

meter move :thumbs:

[strausbo 2]

I am surprised that there have been only one reply to this question?

[Kelly 1,028]

I just seen it, if the batt. is fully charged it should not read much at all, try hooking up afew lights to load the batt. and see what happens, or if all else fails use a test meter to see the out put of the gen.

[IDriveWheelHorse 0]

I agree with Kelly.

Check the output at the generator.

Your rectifier or voltage regulator may be bad. I know alot of the time on the stator charging system the gauge will "flicker" back and forth between 0 and +10 while running, and this is normal.

Also, on a point ignition system or while cranking (or even if you turn on headlights) your ammeter should show draw (needle pointing to the - side).

My two cents, if your gauge is bad, throw in a Volt gauge from harbor frieght for 8 bucks.

Shows voltage instead of amps... (In my opinion, more modern and fool proof)

[Kelly 1,028]

Watch using a volt meter, I have not done it yet to see, but I was told the tractor will not run with that set up??? I don't know why?? I've been meaning to try it.

[Save Old Iron 1,563]

strausbo,

i must have missed your post completely

a couple thoughts

1/ run the battery down with some 12 volt accessory or headlight - something that will draw significant current. When the battery voltage is down around 11 volts, start the tractor and the ammeter should jump to the + charge side - by a considerable amount.

2/ as suggested before - check the battery voltage while the tractor is not running - should be around 12.something, and then again with the tractor running. The voltage at the battery will depend on the mechanical settings of the regulator assembly. As primitive as they are, its hard to quote an exact voltage expected, but it should be up over 13. something - ideally around 13,6 volts.

3/ the ammeter can be checked with a couple of jumper leads. Jumper one side of the ammeter to a 12 volt lamp/ headlamp- the other to the battery. With a headlamp, the current draw should show up around the 3 - 5 amp range. Just reverse the leads to the ammeter and now the pointer should show an opposite 3 - 5 amp indication. You could also do a continuity check with the low range on an ohmmeter. A good ammeter will actually show up as almost a short circuit on an ohmmeter. A defective ammeter will show up and an open circuit.

4/ you could TEMPORARILY (less than a minute or so) ground the Field terminal of the regulator, that will force the SG motor to produce maximum output, Even with a fully charged battery, the SG motor will attempt to overcharge the battery and show a charge on the ammeter. Of course, make the check and remove the ground from the field terminal, You should be able to accomplish the check in less than a minute and then remove the jumper to prevent overcharge of the battery.

Personally, I would check the ammeter gauge first, then perform the other tests as you see fit.

And Thanks,

Checking an ammeter gauge - a good lesson to post in an upcoming SOI University class.

[Save Old Iron 1,563]

Watch using a volt meter, I have not done it yet to see, but I was told the tractor will not run with that set up??? I don't know why?? I've been meaning to try it.

depends on what you mean by substituting a voltmeter for an ammeter.

YOU CANNOT just take out the ammeter and wire the same leads from the ammeter to the voltmeter. Ammeters have an internal shunt inside to act as VERY LOW ohm resistor and the ammeter pointer actually reads a very small voltage dropped across this low resistance shunt.

A voltmeter is purposefully designed with a VERY HIGH internal resistance so as now to draw any significant current from the circuit it is placed into - no significant current (more than a few milliamps) will flow thru a voltmeter.

So, if you remove the ammeter - connect those two wires together with a ring terminal , place the ring terminal on the voltmeter + side and run a ground lead from the voltmeter - to the chassis, yes, the voltmeter will work in the ammeter chassis hole

diagram to follow in case anyone is interested in this conversion.

p.s an ammeter is actually a millivolt voltmeter in disguise. an ammeter will read what SMALL voltage drop is developed across an internally mounted shunt (resistor).

[Save Old Iron 1,563]

here you go

to replace the ammeter with a voltmeter in the existing chassis cutout

Attached Image (Click thumbnail to expand)

[IDriveWheelHorse 0]

here you go

to replace the ammeter with a voltmeter in the existing chassis cutout

Thanks Kelly and Save_old_ iron....

That makes sense being an ammeter reads amps (Flow of current) would be both positive leads to the gauge.

Now that I know, I will have to give it a shot.

I will have a write up on here eventually on a couple modifications that I have done on my 8-25 and Boat.. could be used on just about anything with a battery. Works similar to that of the Battery light in automobiles. I use a comparator circuit to measure voltage at two spots, and when the voltage reaches a threshold it illuminates a battery light letting you know that you have a fault in your charging system or a low battery.

Same circuit for a temperature light and oil pressure light.

I am going to build one for my C-145 and put it in place of where the hour meter would go (if it had one).

Like I said I will have a write up and pictures soon. Someday... If I ever get a couple consecutive days off of work. :thumbs:

[Save Old Iron 1,563]

I use a comparator circuit to measure voltage at two spots, and when the voltage reaches a threshold it illuminates a battery light letting you know that you have a fault in your charging system or a low battery.

Same circuit for a temperature light and oil pressure light.

IDriveWheelHorse

your reading right from my book, perfect idea.

I have started to put together a few ideas on LED indicator gauges to incorporate in my C175 rebuild . Replace the dash panel with smoked Plexiglas, mount gauge like indicators behind the panel and get Decal Wizard to print off some transparent gauge "faces" custom made to look like anything you like.

Thinking of calling the project the "BlackHawk BlackHood" with a high tech military type look. Magnetic based safety switches, forward looking infrared readout for possum avoidance during night time mowing, depleted uranium pinion gears, all the good stuff.

We should chat one these nights !

If you need any help - let me know.

[puddlejumper 67]

QUestion SOI since 1 ammeter wire is hooked directly to the positive side of the battery wouldnt you ned a switch in your ground wire to keep from draining the battery during shutdown hours.

Or is the resistance highenough that it would take months.

[Save Old Iron 1,563]

Good catch - overlooked that concern

but your right - with just a few milliamps flowing thru the gauge, it would take MONTHS to drain the battery.

However, I think you point is valid, I would prefer to have nothing connected to the 12 volt wiring with the ignition switch off.

Realistically, a voltmeter would be an extremely low failure rate item and if it were to "short out" , the small gauge wiring internal to the meter would fry and act as a fuse to keep the voltmeter + terminal from shorting to ground.

As far as battery drain, lets say we have a 240amp hour battery.

Voltmeter draws - lets say - 0.010 amps - so it will draw 0.010 x 24 hours = .24 amp hours per day

240 amp hours / .24 amp/ hr per day = 1000 days for the battery to reach a discharged state from the voltmeter current.

These calculations are theoretical and and rough cut, but you get the idea on how insignificant the current drain thru the voltmeter will be. The self discharge of the battery would be more significant than the voltmeter drain.

really good point - thanks

[JimD 3,345]

I use a comparator circuit to measure voltage at two spots, and when the voltage reaches a threshold it illuminates a battery light letting you know that you have a fault in your charging system or a low battery.