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       #1  

    Generator overload. Gen ovld

    I was AOG in ILG (Wilmington, DE) with a GEN OVLD CAS message the other day. (I’m giving a shoutout to the MRO that helped me get on my way in another post and suggesting a new area for our website). On start up the readings were showing 540 amps from the left generator and even with the engine shut down, still showed extremely high amp readings for a substantial time. QRH says turn off the A/C, then the windshield heat but those are both off on startup. I’m bringing this to others’ attention because the fix does not appear logical and we trouble shot a lot of other items first. There is a Generator Shunt for each starter generator. It is a high amperage very low resistance terminal block (about .1 ohms) that appears to be just a grounding terminal for the S/G, but it is needed to provide an accurate reading for the galvanometer. EMB tech support said to clean the Generator Shunt according to the AMM and if that doesn’t work swap the left and right to see if the problem goes to the other side. Cleaning the shunt is a 60 month maintenance item. Without removing the shunt, one of the first things we checked was the resistance across the shunt and the resistance was nominal. Only after removing it, cleaning it and replacing did we get proper readings, even though we saw zero corrosion on any terminals.
    The EMB service desk was very responsive. The AMM does not have a trouble shooting task for this item.
  2. Username Protected
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    #2  
    Hello Aron,

    The AMM a mentions the GEN OVLD CAS message is triggered when S/GEN 1 or 2 is overloaded and it is inhibited during assisted cross engine start. Not sure if this was your condition when you first got the CAS msg.
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       #3  
    Correct CAS message but what caused the message was the generator shunt resistance increasing making the readings unreliable, not the generator being overloaded. This is a good explanation of how the generator shunt (shunt resistor) works that i found. https://eepower.com/resistor-guide/r...unt-resistor/#
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    #4  
    Oh I see. Yes, you’re absolutely right, this is a very common issue. Cessna citations call it a ground fault and was corrected by bond preping the mating surface of the Generator’s negative terminal. I wish Embraer would implement the type of GCUs found citations which have troubleshooting led indicators. Thanks for sharing (Username Protected)!
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       #5  
    That would be nice!

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