High voltage problem

[rv9aviator]

I am trying to help a friend with an RV 6A solve his alternator problem and could use some advice on where to start. This is a ND alternator with Ford regulator. Everything was fine until the volt meter started showing 15.5 to 16 volts. Then an over voltage alarm came on on one of the instruments. He thought the regulator went bad so he replaced it. He still has 15.5 to 16 volts now. If he didn't have a good ground from the regulator case to the airplane would that have any bearing? He also plugged in a voltmeter in the cigar lighter and it shows the same voltage as the instrument in the panel so I'm sure it isn't the gage. Where should I start looking? Thanks in advance.

[Dean_aeroleds]

Here is a description of how the regulator works:

"The regulator is the brain of the charging system.

It monitors both battery and stator voltages and depending on the measured voltages, the regulator will adjust the amount of rotor field current to control alternator output.

Regulators can be mounted both internal or external. Current technology uses an internal regulator."

So, if the regulator isn't damaged, but is producing a too-high voltage, it is probably because it isn't correctly measuring the battery or stator voltage, and is driving the voltage high because it thinks the battery voltage or stator voltage is low.

Is your battery connected correctly to the alternator?

[rv9aviator]

Will check into that tomorrow. Maybe there is a bad connection between the battery and the alternator. Could a bad battery as in shorted or open cell cause this. BTW, I received my full Aero-LED lighting system from Stein last week and it looks awesome. Can't wait to get it installed.

[aerhed]

You could have high resistance across the field switch or in the field wire. This tells the regulator that voltage is low so the regulator raises it's field voltage. Kind of common on Cessnas with Ford regulators/alternators.

[rv9aviator]

By field switch are you referring to a panel mounted switch to break the field wire from the alternator? I haven't checked to see if he even has an alternator switch yet. The information I have is just from a phone conservation. Tomorrow I will check everything out, but I understand now that I need to check wiring from the battery and the field wire for problems.

[vlittle]

Originally Posted by rv9aviator

By field switch are you referring to a panel mounted switch to break the field wire from the alternator? I haven't checked to see if he even has an alternator switch yet. The information I have is just from a phone conservation. Tomorrow I will check everything out, but I understand now that I need to check wiring from the battery and the field wire for problems.

Here's what I did to fix the same problem on my 9A:



The Ford regulator (I think) has a sense input that could be connected directly to the battery to remove any of the problems of resistance in the Field circuit. I used the Van's regulator, and this schematic solved my problem completely.

V

[rv9aviator]

Thanks everyone for giving me a direction to trobleshoot my problem. It was a simple issue with the field wire coming off the ALT switch on the Cessna type batttery alternator panel switch. Thanks again