1961 Cessna 172 B O300 generator

Did you turn on the engine? Just wondering cause you know the post is epically short.
 
You may want to charge the battery and get it charged back up while we sort through your post. Lot to analyse...
 
Battery taking out of aircraft and charged at a 2 amp rate. Battery is only one month old. After charge over night, voltage read 12.6 volts. Battery reinstalled in aircraft. With master on, voltage read 12.6 at accessories plug. Aircraft is a 1961 Cessna 172 B.
 
Yes. Engine running at 1600 rpm with no charging on amp meter.
 
Here's what LEO the AI Chat Bot says to do:

Flash the generator field​

Flash the generator field is a process used to restore residual magnetism in the exciter and generator fields of a generator. This is necessary when the generator voltage does not build up and the generating system does not have field flash capability.

Why is Flashing the Generator Field Necessary?
Flashing the generator field is required when the generator voltage does not build up and the generating system does not have field flash capability. This condition is usually caused by insufficient residual magnetism in the exciter and generator fields. Residual magnetism can be restored by flashing the field, causing a current surge in the generator.

How to Flash the Generator Field
There are several methods to flash the generator field, including:
  • Using a Battery: Connect a 12-volt battery to the exciter field while the generator is at rest. Remove the exciter field leads from the voltage regulator and connect the battery to the exciter field. This will restore the residual magnetism necessary to begin voltage buildup.
Precautions
  • CAUTION: Failure to remove the field leads from the regulator during flashing procedures may destroy the regulator.
  • Ensure proper safety precautions are taken when working with electrical systems.
Conclusion
Flashing the generator field is a simple and effective way to restore residual magnetism in the exciter and generator fields of a generator. By following the methods outlined above, you can ensure that your generator is functioning properly and producing the desired output.
AI-generated answer. Please verify critical facts. Learn more
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How old is the generator?

Just get to overhauled and once that's done think about troubleshooting
 
flyboy95977 said:
Battery taking out of aircraft and charged at a 2 amp rate. Battery is only one month old.
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FYI: charging a depleted battery at 2A vs following the OEMs recovery charge instructions can cause a permanent loss of battery capacity.

As to the original problem not enough info even to make an educated guess. Perhaps chase some voltages with a meter to find where your voltage starts and stops? Or get someone to help before more battery loss occurs.
 
This is not a problem for an aircraft owner to solve. It's for a capable mechanic. An owner can cause significant damage by fooling with stuff he doesn't understand, and then the expenses really pile up.

For instance, nothing shows on the ammeter at 1600 RPM. That could mean a bad generator, bad or corroded connections, bad regulator, bad master switch (which, in a 63-year-old Cessna is highly likely, as the lube in the push-pull master switch goes hard with age and prevents the regulator control contacts from contacting), bad generator fuse (it can look good but be corroded inside and not conducting), or even a bad ammeter. If you don't know how the system works and can't read the wiring diagram, and don't have (and don't know how to use) a multimeter, you have little chance of fixing anything.
 
I agree with Dan that some of this is best done or supervised by

an A & P although the Cert alone will not make them extremely generator

knowledgeable. All tests with the engine running should be done with

lights and avionics OFF.

The most difficult part of diagnosis would be dropping the cowl.

There are several ways of doing this.

Some would involve using your Harbor Freight Aircraft Test Lead Kit.

Momentarily grounding the FIELD terminal should give full generator output.

Note Momentary!

However; there can still be issues with whether Gen is charging or charging

and not indicating.


There are those that will say just install an Alternator.

That is nice but not exactly plug n play especially if done correctly.

Gens do suffer from lack of knowledgeable maintenance though.
 
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