Need Help with Z leveling

I’ve searched and read the other topics regarding z leveling. Still having issues. Here’s my latest numbers.
First: Z1 is at X max position. Z2 is at X 0 position. Both are connected to the correct board positions. the Z axis moves as expected, no racking.

I’m using a touch plate for z leveling.
I home Z by G28 Z0. Both Z1 and Z2 steppers home as expected. Current position is @ X0.
Initiate G38.2 Z0. Z descends as expected. Contacts touch plate and stops.
M114 shows Z of 138.59. Home Z (G28 Z0)
Move X to far end (Z1 stepper side)
initiate G38.2 Z0. M114 shows Z of 135.73.
Delta of 2.86 (Higher number at X0 position).
I enter M666 Z2.8
I then enter M500
Run G28 Z0. Z homes and the stepper at X0 descends slightly, assume this is the offset I just entered.
Double check everything again.
Now, Z level at the X0 side is 140.89 and at X max end is 136.11.
X0 side lowers, as expected, but the Z reading increases? Delta now 4.78.

Am I misunderstanding something here?

Firmware screen shot:

Have you tried M666 Z-2.8?

I can never remember which way it corrects, but it sounds like your correction was in the wrong direction.

Yep…tried that. same issue.

Grubs screws are tight, right?

Yep…grubs tight.

So, this may or may not have been the issue. Others have posted that things were not working as expected, then a day later they did. I thought that maybe something happened in firmware. So I downloaded the latest version - managed to find an 8 gig micro SD and flashed the board late last night. Just finished Z leveling. 2 cycles of adjustment and got to +/- 0.21 mm (0.008 thou). I’m good with that.

Can’t explain it, won’t even try. Could be operator error, could be something else. But it works now and time to move on to the creative side!

I do have a question though. With all this adjustment, I noticed that the EEPROM save locations are counting down…gone from 20 to 8. What happens when / if you get to 0? Smoke/Fire? Crash & burn?

Thanks to all with your suggestions.

I think you can always choose to overwrite an Eeprom slot that had previous values store in it.

just for future reference…how?

Well, I may have misspoken. I think I confused EEPROM with saving mesh records from UBL. I guess I need to retract that answer. :slight_smile:

For what it’s worth, everytime I do M500 to save to EEPROM, it just works. I’ve never been aware of slots for that, or counting them down, or managing them. I need to let someone else who knows more clarify if I’m off course.