MPCNC Rambo Dual endstop ALARM:8 (Homing fail)

2 year old MPCNC Rambo Dual endstop GRBL on CNCjs. was running beautiful 2 months ago. started it back up, hit the blue homing button and X moved 3mm in positive direction and ALARM:8 (Homing fail). Did status report ? on each of 4 switches X1(<Idle|WPos:3.000,-1.500,0.000,3.000,-1.500|FS:0,0|Pn:YXYH>) Y1=Y gone, X2=X gone, Y2=Y gone. Turned soft limits off and jogged machine, all move correctly. Moved X and X2 to start touching switches and hit homing X keeps going in negative direction skipping belt teeth. have not changed anything sense last run.

$0=10 (Step pulse time, microseconds)
$1=255 (Step idle delay, milliseconds)
$2=0 (Step pulse invert, mask)
$3=21 (Step direction invert, mask)
$4=0 (Invert step enable pin, boolean)
$5=0 (Invert limit pins, boolean)
$6=0 (Invert probe pin, boolean)
$10=16 (Status report options, mask)
$11=0.020 (Junction deviation, millimeters)
$12=0.002 (Arc tolerance, millimeters)
$13=0 (Report in inches, boolean)
$20=1 (Soft limits enable, boolean)
$21=0 (Hard limits enable, boolean)
$22=1 (Homing cycle enable, boolean)
$23=27 (Homing direction invert, mask)
$24=500.000 (Homing locate feed rate, mm/min)
$25=2000.000 (Homing search seek rate, mm/min)
$26=250 (Homing switch debounce delay, milliseconds)
$27=3.000 (Homing switch pull-off distance, millimeters)
$30=1000 (Maximum spindle speed, RPM)
$31=0 (Minimum spindle speed, RPM)
$32=0 (Laser-mode enable, boolean)
$100=100.000 (X-axis travel resolution, step/mm)
$101=100.000 (Y-axis travel resolution, step/mm)
$102=400.000 (Z-axis travel resolution, step/mm)
$103=100.000
$104=100.000
$110=7200.000 (X-axis maximum rate, mm/min)
$111=7200.000 (Y-axis maximum rate, mm/min)
$112=400.000 (Z-axis maximum rate, mm/min)
$113=7200.000
$114=7200.000
$120=400.000 (X-axis acceleration, mm/sec^2)
$121=400.000 (Y-axis acceleration, mm/sec^2)
$122=200.000 (Z-axis acceleration, mm/sec^2)
$123=400.000
$124=400.000
$130=600.000 (X-axis maximum travel, millimeters)
$131=600.000 (Y-axis maximum travel, millimeters)
$132=120.000 (Z-axis maximum travel, millimeters)
$133=600.000
$134=600.000
$140=135.000
$141=135.000
$142=135.000
$143=135.000
$144=135.000
$150=0.000
$151=0.000
$152=0.000
$153=0.000
$154=0.000

Sounds like the switches are wired wrong. Should be wired normally closed.

Also, if it actually skipping belt teeth and not just skipping steps (not that easy to tell the diff), then your belts may be too loose. I always make a sharpie mark on my pullies, so I can see visually if I’m dealing with slip vs skip.

thanks for the help. Set $5=1 and homing works, my concern now is GRBL says i need a pull down resistor, what size and where to put it.


thanks again