Garage door problem - troubleshooting suggestions


We've had a problem with our garage door opener for a few months now, and since winter is coming we are using it a lot more. I can't really afford to call someone out right now, so I've been trying to figure out what I can do to try to troubleshoot the problem myself. Here is what I've come up with so far. Does anyone have any suggestions? Might I be barking up the totally wrong tree? Thanks! -Bob
The problem:
The garage door will not close normally with a single push of the operation button, or through use of the remote control. To close the door, we need to hold down the button until the door is completely closed, otherwise, the door closes a couple of inches and immediately "bounces" back open.
This situation is unacceptable both because of its inconvenience and because it's potentially unsafe for our three cats and one two year old.
The parts:
There is an Allister Access 3000 automatic garage door opener. There are two screw terminals on the opener have a two-conductor wire attached that leads to the left side (standing in the garage facing out) entrapment photo sensor. There is another two conductor wire that leads to the right side entrapment sensor from the left sensor.
Troubleshooting technique:
1) Using my digital multi-meter, touch one lead against each of the screw down terminals of the closer and check for any voltage when the door is attempt to be closed. TODO: see if I can find out what the expected voltage should be.
2) If I get a voltage measurement on step 1, then check the conductors going to the left-side sensor for voltage and see if it's similar. If it's not then I can assume that there is a problem with the cable run from the closer to the left sensor. If there is, then go to step 3.
3) Check for voltage at the left sensor terminals that lead to the right sensor. TODO: see if I can find out what the expected voltage should be here. If I get voltage here, then go to 4.
4) Check the conductors at the right side sensor for voltage. It should be the same as 3. If it isn't then I can assume the there is a problem with the cable run from the left sensor to the right sensor. If it is the same, then go to 5.
5) Assume the problem is either faulty sensors or misaligned sensors. Is there any way to test the sensors? Perhaps with short speaker cable runs and holding them directly across from each other?
6) Buy new sensors.
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Bob the Brewer wrote:

Typically, you can override a safety sensor reversal by holding the manual button down.
Does the light bulb on the motor unit flash when the door is trying to close and bouncing? Not sure if all units operate this way, but some units will flash the light if the door is reversed because of the safety sensors.
Look at the safety sensors themselves. One is a light source, and the LED indicator on it should be lit all the time. The other is the receiver, and if everything is OK, the LED indicator on it should also be lit. If there's a problem, the LED could either be flashing, or totally out.
If you think it's the sensors, there's a couple of possibilities: - Dirty lenses, clean them. - Sensors knocked out of alignment, align them. - Broken wire to sensor, fix it. - Too much direct sun on receiver sensor, shade it or reverse source and receiver
I would check the above possibilities before I bought new sensors. I actually had the 3rd problem at one time. New house, builder-installed opener, worked fine January through June. Then we started having problems with the door not closing, but only in late afternoon. Conclusion - summer sun in late afternoon was blinding the receiver. Solution - positioning a plant near the garage to shade the offending sunbeam.
Hope this helps, Jerry
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Sounds like the auto-reverse adjustment is too sensitive. It's supposed to reverse when it senses some resistance, like that of a car roof, but if it is automatically reversing without hitting anything, either the adjustment is out of whack (that you can fix), or the door and springs are way out of balance (that requires a pro to fix).
To see if the door is out of balance, disconnect it from the opener and pull it halfway down, then let go. Does it stay there? If so, it's ok. If it goes up more than a few inches(as I'm guessing it will), the springs need to be adjusted or replaced. Look at the size of those springs - do you want to mess with them?
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The Solution:
The photoelectric eyes should have LEDs which supposed be lit, if one is out or flickering Check the electric eye's for alignment, dust, dirt or other obstruction. Check the eye's wires to see if it may be disconnected or damaged, reconnect or replace as needed.
Rich http://www.garagedoorsupply.com
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Rich wrote:

I agree with Bob. This sounds like a down force setting problem. The doors are typically set up to reverse if either the force becomes too great, or the sensing beam is interrupted. If the door starts down, then reverses, it's not likely a photo sensor issue, because if that were the problem, it should not start to move. There should be an adjustment on the opener for both down and up force limits. Also, make sure the door is nearly balanced and moves up and down with little force.
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The stop adjustment for the closed state of the door is out of adjustment. Make your door stop earlier.
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Thanks for the replies so far!
snipped-for-privacy@mucks.net wrote:

I might not have described what it does very well.
If I push the button on the remote control or on the wall control, it starts going down, then immedaitely stops and goes right back up. It doesn't go down more than an inch or two before stopping and coming back up.
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Bob the Brewer wrote:

Might or might not move at all if it's the safety sensors. Worth a look.
If it moves an inch or 2 and reverses, other posters could be right, could be down force sensor, may need adjustment, or door could be binding, or springs could need adjustment. Springs, I wouldn't touch them myself, too dangerous.
Jerry
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wrote:

So it reverses at a mid way point ?..................If so then unhook the drive and open the door by hand. See if you feel any out of the ordinary drag on the door. See if it seems to be counterbalance properly.
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