AA5 Grumman charging system

[Mark Nestler]

On a 1975 AA5 Traveler my voltage indications occasionally drop off to 12.2 or battery voltage. Normally, there is 14 or 14.1 indicated on the meter. Should the charging system suddenly drop to battery voltage or should it gradually taper off as the battery reaches fully charged? I have changed out the Master Switch and repaired a loose connection on the ALT side of the Master switch. If I cycle the ALT switch to OFF and back ON the voltage indication will jump back up to 14 volts for a period of time until it again drops back to 12.2. I have not noticed it climbing back up to 14 volts unless I cycle the ALT switch.

 

[Bell206]

my voltage indications occasionally drop off to 12.2 or battery voltage.

Well if your static battery charge is only 12.2 volts after being charged at 14.1 volts I'd say you first need to verify the health of your battery and the voltage regulator system for serviceability before throwing any more parts at it. Could be a number of things causing this issue.

 

[Mark Nestler]

The 12.2 value is what is indicated on the aircraft digital voltage meter. I brought the battery home and let it sit on a charger overnight. I checked it with my Multimeter
and got 13.1 volts. Not that it proves that the battery is 100% healthy. The new battery was installed AUG of 2020 and could probably use a load test with someone who has the right equipment.

 

[Bell206]

I checked it with my Multimeter and got 13.1 volts.

Let the battery rest for at least 4 hours, preferably 12 hours, and recheck the resting voltage. Depending on battery model should be around 12.6 volts.

could probably use a load test with someone who has the right equipment.

A poor man simple load test is to apply a .5 - 1 amp 12v load to the battery for 30 mins then see what change to the resting voltage there is. If it is back to your 12.2 reading I'd get the battery properly checked per the OEM procedure. Regardless, I'd also get with your mechanic and find the troubleshooting procedure for your voltage regulator system and start checking voltages. Could be as simple as another loose or corroded connection if your battery is good.

 

[Skip Miller]

Please check your multimeter against a known high quality meter. I've seen multimeters range in price from $8 to well north of $150. (The former being a Radio Shack special, and the latter being a Simpson 260 meter in 1970 or so).