Regulator?

[68niou1]

Hi guys, Early Rotax 912 UL 80 hp, just installed a MGL Extreme and I keep getting over voltage alarms- voltage varies from 13.5 all the way to 16.7. I changed the regulator with no difference. My question is what is normal? My friends Rotax does not vary any where near this much. My problem is this might be normal for my plane, I just have never had instrumentation to know. Thanks-

[PapuaPilot]

No that doesn't sound normal. A regulator usually holds the voltage within 0.1 volts.

I don't know your system, but typically 12 volt systems will regulate around 14.0-14.5 volts.

Do you have any intermittent loads like flashing lights, strobes or wig-wag that draws high amps? That could be a cause.

Can you adjust your over voltage alarm threshold on the MGL? If so try increasing it to 16 volts or higher.

Does your electrical system have a big capacitor in the charging system? It could be a cause if it has gone bad.

[68niou1]

No that doesn't sound normal. A regulator usually holds the voltage within 0.1 volts.

I don't know your system, but typically 12 volt systems will regulate around 14.0-14.5 volts.

Do you have any intermittent loads like flashing lights, strobes or wig-wag that draws high amps? That could be a cause.

Can you adjust your over voltage alarm threshold on the MGL? If so try increasing it to 16 volts or higher.

Does your electrical system have a big capacitor in the charging system? It could be a cause if it has gone bad.

Thanks for the reply-

Basic system with no lights, just basic radio,intercom, gps, MGL and transponder. I do not believe it has a capacitor in the system- but I am careful not to kill the master before I shut the engine off. I'm wondering if there is something wrong with my sense wire, anything special I should look at impedance wise on that wire?

Thanks again,

Scott

[PapuaPilot]

Again, I don't know your system. Do you have a schematic?

The sense or field wire could be possibilities. It could also be a problem with he alternator.

[68niou1]

Found it. Turned out to be a loose screw on the back of a circuit breaker(the one that is hooked to the sense wire). Amazing how a loose screw can cause such huge deviation! Thank you PapauPilot for your input-

Scott

[efwd]

Sweet! If only all the electrical Gremlins could be resolved this quickly.
Eddie

[jiott]

I still think you need to install a large capacitor like all the Rotax installation schematics show.

[68niou1]

I still think you need to install a large capacitor like all the Rotax installation schematics show.

Definately a good idea, I agree.:D

[Slyfox]

scott. one thing you need to know about the rotax regulator. they do not like to be shut off when the engine is running. do not, I repeat do not check the alternator like we were taught in flight school. just look at your voltages and say, yup it's working. turning off the field for the alternator will kill the regulator. take care.

[68niou1]

scott. one thing you need to know about the rotax regulator. they do not like to be shut off when the engine is running. do not, I repeat do not check the alternator like we were taught in flight school. just look at your voltages and say, yup it's working. turning off the field for the alternator will kill the regulator. take care.

Thanks Steve- appreciate the input:D

[Esser]

scott. one thing you need to know about the rotax regulator. they do not like to be shut off when the engine is running. do not, I repeat do not check the alternator like we were taught in flight school. just look at your voltages and say, yup it's working. turning off the field for the alternator will kill the regulator. take care.

I’ve been looking through th deep dark places to find information on this. One source says once the field is energized, you can’t turn off the output of the alternator. AeroElectric Connection touches on PM alternator such as the Rotax internal alternator, then it says it will discuss more in the next chapter, and the. In the next chapter doesn’t really say anything.

So my question to you is removing the field what is cooking all these regulators? Another forum said that if you ran the ext. alt and the internal alt in parallel like Rotax suggests, the ext alt would take all the load (higher set voltage) and the internal alternator would continue to make power but would not be using it (until the ext alt was fully loaded and the voltage dropped to the same level the int alt was set at) and toast the regulator. I have read in a few places to keep the regulator happy, keep load on th internal alt.

I guess my question is, is it actually safe from a regulator health point of view to run these alternators in parallel with the int alt taking almost no load?