PS3 loco "surging"

Usually a tach issue.  Alignment with the striped flywheel, gap to that flywheel, broken wire or bad tach.  Start with an inspection under the hood.

Jon is most likely right.  I've did run across one that had the flywheel loose on the shaft, that will obviously cause this issue as well.

I had my local repair guy replace the tach reader and check everything out. Still does it.

Does it do this at the same locations on the track?  What is the loco?  What is the time interval of the speed cycle?

Might be something helpful in this thread. My problem turned out to be the transformer, but a lot of good ideas here.

https://ogrforum.com/...c/155716354279799980

@Ralph M posted:

I had my local repair guy replace the tach reader and check everything out. Still does it.

Post up the item number of the locomotive, and what did your local repair guy say what he found to be wrong?…..sounds like he tossed parts at it in hopes of a Hail Mary …..

Pat

He assumed like everyone else that it was the tach reader and replaced it. He swears that it operates normally on his test loop. But it acts like this on my layout. I have nearly 100 locos and none of them do this.

Get back to basics.

How does it run in conventional mode?

Run the engine by itself on a test track do the same symptoms persist?

Remove the variables caused by your consist, track, and transformer. Heck I'd even turn it upside down and run it at various speeds with alligator clips providing the power. This will give you good visuals as to the performance of the motors. Monitor amperage draw closely.

Try it without the trailing “A” unit in DCS and conventional.

Possible loose motor.

@Jon G posted:

Try it without the trailing “A” unit in DCS and conventional.

The trailing A unit is a dummy

Wondering now if one of the worms, driven gear or striped flywheels are loose.  Pull the shell, hold the wheels tight while you turn each flywheel.  Run it with the shell off and note the motor speeds.

It behaves the same in conventional mode

Other things I've tried:

Engine reset both feature and factory

TIU reset both feature and factory

Loaded it into a different remote.

Track signal test 10 out of 10

Track voltage 17.9 (using an 18v supply)

@Jon G posted:

Wondering now if one of the worms, driven gear or striped flywheels are loose.  Pull the shell, hold the wheels tight while you turn each flywheel.  Run it with the shell off and note the motor speeds.

I've seen a loose flywheel do some really odd things, especially the one with the tach reader.

Checked both motors: Flywheel, worm gear, motor mounts, Nothing loose.

Thanks for the update.  About a dimes worth space between the tach and flywheel works.  The heavy rubber band used around the motor to secure the wires can be moved up to the bottom of the tach bracket to help pull it away from the flywheel.

@Jon G posted:

Thanks for the update.  About a dimes worth space between the tach and flywheel works.  The heavy rubber band used around the motor to secure the wires can be moved up to the bottom of the tach bracket to help pull it away from the flywheel.

This is one I'll definitely remember for a long time.

I use .8 to 1.0mm spacing for the flywheel sensor, that's the "sweet spot" for the sensor used, the Omron EE-SY124.  I have a .9mm strip that I use to space the sensor.