This statement sure has me confused "Also when I opened the cover to replace the stripped drive gear, the interrupt cup had fallen off. I put it back on the shaft but I don't know it's function." Do you really mean the cup was off when you first looked at the stripped gear or fell off after you had replaced the gear?

Take a look at the limit switch assembly and make sure the down contacts are not touching when the door should be moving down. You may have added problems to your problem.

The interrupt cup was off the shaft and jammed against the logic pc board when I opened the case. Right now the limit switch down contacts are not touching, but as I mentioned, I adjusted the contacts when the motor wouldn't run. However, the door was moving up when the gear stripped. You are right that I added problems to my problem. In fact I think that IS now the problem. Thanks for your reply.

PS I still don't know the function of the interrupt cup.

Hi norcris, the interrupter cup rotates thru a small sensor beam on the rpm board and the pattern of makeing and breaking the beam makes a signal the MAIN logic board needs to see to allow the motor to run. If the cup is off, no signal=logic board thinks the motor is not turning=logic board thinks door is jammed on something.

Push the cup on all the way, its paddles must reach down inot he slot on the rpm board-slot is on side closest ot the motor shaft.

Did you try to change the worm gear??

A

Hi techdave, Thanks for replying - The cup is pushed all the way onto the shaft. I didn't change the worm gear which seemed ok --only the drive gear. They seem to mesh well. I can rotate the shaft with my fingers. Neither up nor down limit contact is touching. The motor still doesn't start. To complete the picture of the situation, the trolley is positioned about half way along the track.

Question: How does the motor start if it requires the on-off signal produced by the interupter in order to run?

Thanks for your help/

yo n, if you get click not a hum, but that's all, check that all motor wires are still connected.

the signal from the interrupter is to keep it running , not for starting.

either motor lead to white should be 1/2 the ohms of red lead to blue lead. No continuity ot the case of the motor.

Thanks again techdave. I checked the wiring and it seems ok. Resistance blue to red = 6.8 ohms; either to white = 3.4 ohms. I decided to give up and bought a new Craftsman 1/2 hp so I could use the existing hardware and just replace the drive head. The manual that came with the new one had more diagnostic information than the original. The new manual says that the repetitive five blink code along with no motor hum indicates the logic board is bad. Anyway I appreciate your help. At least I learned what the interupt cup is for. Thanks again. Oh, incidentally, I had hoped to use my old remotes with the new system. Followed the "learn" instructions but couldn't make them play. I'm guessing that an eight year old remote may not have the so called rolling code technique.

Regards,

norcris

You new model number probably ends in D. Its on 315 Mhz, the old one was 390. Incompatable. Sorry, Dave.

After installing my 1/2 hp craftsman garage opener when I push the elec control it only closes one foot and goes back to open. What do I do ?