Charging ANOMILIES

The following situation is baffaling to me:
Several times since finalliy starting this Farmall BN I
have had to utilize the crank because the elrctric
starter / battery failed to turn the engine over. This
has often happened when I have started and done several
short low speed runs.
Out of desperation I put e volt meter on the battery
today******** results****** at idle voltage jumps from
5.0 to 12 or 13 v ON A 12 VOLT GENERATOR: at half
throttle the voltage jumps from 5.0 to 18 or 19 volts.
Both flash between the lower and upper numbers and back
down and up again then down.
Here are things I have already completed; re checked the
polarity and ran the gen with field grounded and armature
to battery, opened gen and rechecked brush ware and ease
of movment.
THE GEN IS A DELCO REMY 1101980 6A 18 As per the id tag.
The battery is a small 12v often used on the likes of a
small car and is a closed type so I am unable to check
liquid levels.
All feed wires are new and 10 gage from gen to regulater
to pannel.
!!!!! I am absolutly baffeled!!!!
Any other questions that I may not have addressed
Please let me know and I will do my best to answer.
Other than the above
???? What do I check next, or do????
Thank you for your insights.
Wm

Chuck the digital meter in favor of an analog meter, so you can actually know what is happening.

I will second dumping the digital volt/ohm meter for this application. Get an analog meter and check the voltage with it. The trouble is the digital meter is picking up fluctuations in the voltage that are changing faster than it can display/read them. When you check the same circuits with the analog meter you will see the needle swinging and usually you can see the high/low points.

Then once your getting a reading on your voltage check back with us. I am leaning towards a bad voltage regulator causing/allowing wide/wild voltage swings. Your generator can also have issues that can cause this too. One of them being a bad armature.

Per my Delco/Remy reference the 1101980 is 12V, 12A CW rotation and was originally used on Lauson/Techumseh HH80, HH100, and HH120. Earliest date listed is 1963, and last is 1970. And my suspicion because of the listed application is that it was a starter/generator. Uses Delco D655 (subbed from 1118981) mechanical regulator. It could be 18 VOLTS (potential), if there are no AMPS (flow) your battery is not going to charge. Also generators do not put out much current (flow) until they are pretty well wound up. You need to remember that when those machines were built they were working machines that were going to be operated at full power for a working day, not puttsing around the yard at part throttle. Since you are 12V it may be time to consider an alternator that will charge at lower RPM. If you want to keep that setup, figure out the pulley ratio and engine RPM you want to run at, take the unit AND the regulator to your local electrical rebuilder and have him see what it puts out at your parameters.

Check the battery voltage with the engine off.

If it reads low, try doing a slow charge, 2a or so overnight. If it appears to take a charge, see if it will crank the engine over.

If not, have it load tested.

Once a known good battery is in place, check the voltage at full governed throttle. It should be 13.5-14.5v. If it's higher, the regulator is not working, possibly not grounded, or incorrectly wired. Running it that way will damage the generator and battery.

As noted by JMOR, the digital meter is reading instantaneous samples of a very noisy circuit. All old generator based systems and mechanical regulated alternators are putting out a range of static that averages enough voltage to charge the battery. Using an analog meter (with a needle) alows the weight of the needle and its mechanism to average the voltage and stay pretty much steady. A very good Fluke digital will also do the averaging task. Jim