Series C Amplifier Voltage Issues

I have been chasing this issue for at least a month now.

I have a Fanuc 18M Control on a Grinder. My first issue was a 414 error on the Y axis. Long story short after talking with Fanuc:

First diagnostic was Amplifier so I replaced that: Worked for a few days and repeated Error

Second diagnostic was motor: I got the rebuilt, worked for a few days and repeated the Error

Following the books with a 1 bit in the OFS in DNG 204 leads me to Motherboard and Axis Daughter Boards. So we found rebuilts of both: Worked for a few hours then repeated error.

Next we looked at the Amplifier again, as we could have had a bad motor, replaced amplifier and the bad motor took the amplifier out again. Company that sent us the amp kindly replaced it under warranty and we tried again. Worked for a few hours and repeated.

Next we swapped the motors and the issue follow the motor. So we bit the bullet and bought a brand new motor from Fanuc: That worked for a day and a half, but now brought us a more common 411 error and 410 error. Now if I do get a 414 error which only seems to happen if I can actually get the machine to move and it over travels. I get an 8 on the Amp LED.

Now I am looking back at the amplifier. I am getting a solid 220v into all the amps, but on my Y axis Amp I am fluctuation from 110V to 160v (idle) on all three legs output. While the other Amps are solid at 160V constant. Not sure what this means but since X and Y are the same motor, i would think the output voltages should be the same.

The issue now follows the amp and not the motor, if I change Amplifiers

I have tested connections on the cables and see no short to ground and have continuity through all the wires.

Any thoughts as I wait for Fanuc to call me back again???

Thanks for any info
Josh

IIRC these are the drives with the sub miniature connectors plugged into the bottom?
I had one where the connector was bad, if I wedged the connector up into the socket it would run.
Due to all the different scenarios you have, with new motor, new amp, it sounds like it could be cable/connector problem.
Al.