down limits wont stop door

having trouble with my limit switch.  i just installed and a new one.  the up limit seems to work okay but the down limit doesnt stop the door when its supposed to and goes all the way to the end.  there is a 1 sec pause on the down cycle but then it continues as its supposed to.   I have also replaced the rpm sensor.   sometimes i can adjust the down limit way back and it does stop like its supposed to but as soon as i start moving farther down, it wont stop.   any ideas?

It's great that you tried adjusting the down limit. Try it again and this time do it gently. With every adjustment, check the door's movement and continue the process until you find the proper adjustment.

Another possibility lies in your garage door motor. Check if the motor is working correctly.

It sounds like you're having some issues with the limit switch on your garage door opener, specifically with the down limit not functioning properly.

A few things to consider based on the information you've provided:

New Limit Switch Installation:
Ensure the new limit switch is installed correctly and making proper contact with the limit switch actuator on the door.
Check that the limit switch is securely mounted and not shifting position as the door moves.
Limit Switch Adjustment:
The fact that you can sometimes get the down limit to work by adjusting it back, but then it stops working again, suggests the limit switch may need further fine-tuning.
Try making very minor adjustments to the down limit setting, testing it, and then making additional adjustments as needed.
RPM Sensor Replacement:
The RPM sensor is responsible for providing the door position feedback to the opener's control board.
Since you've already replaced this, the issue is likely not with the RPM sensor itself.
Pause in Down Cycle:
The 1-second pause you mentioned on the down cycle is a normal safety feature, but it should then stop the door at the set down limit.
This suggests the limit switch is not properly communicating the door's position to the control board.
My recommendation would be to carefully re-check the installation and adjustment of the new limit switch. Ensure it is making proper contact and not shifting position. You may also want to consult the manufacturer's installation instructions to verify you have the switch set up correctly.

If possible, we are happy to provide online guidance and help, you can contact us: CHI Hardware Co., Ltd.

Or you can directly send us an email about your problem, and we will reply to you as soon as possible after seeing it.
Email: chi@chihw.com