Garage door will not close when it rains

This garage door problem really has me stumped.
Fortunately here in Southern California it doesn't rain too often (except for this year).
But when it does my garage door halts about half way down and then retracts (i.e. opens).
I know this can be a symptom of a door sensor problem. But I just moved in and the infrared sensors, which are usually on either side of the door near the floor of the garage, cannot be located.
It is a Sears 3/4 HP Garage Door Opener (chain drive). Similar to the GDO at http://www6.sears.ca/webapp/wcs/stores/servlet/ProductDisplay?categoryId 686&catalogId001&storeId001&langId=-1&productId8060864
But a bit older, although the GDO technician that came out several months ago said he did not think it was too old (whatever that means). By the way he was also surprised that we could not find the sensors in their 'usual' place.
I lubricated all of the recommended places and even increased the screwdriver adjustment for the door closing speed/pressure. Still no joy.
Any ideas?
As always, thank you for your time.
Michael
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Since you say it happens when it rains, I suspect moisture fouling up electronics. You might try some Caig contact cleaner (Radio Shack) on the controls (remote, wall, opener) and see if the issue goes away.
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snipped-for-privacy@yahoo-dot-com.no-spam.invalid (borgunit) wrote:

i've noticed my garage door gets heavier after a rain. I saw on one door, that said paint both sides, I guess because they warp , when they absorb moisture. good luck.

MONEY , what a concept
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EVERY surface on a door should be sealed to slow water migration. My sisters doors get hard to close when humidity is high but my BIL is too hobbled with arthritis to pull the hinge pins so the bottoms can be sealed.
On Thu, 28 Apr 2005 12:12:03 -0700, BananaRepublican

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I think you are on to something as when I cycled the power the partial closure problem went away. I should add that sometimes it also will not OPEN all the way. It stops 1-2 feet from the fully open position.
Lucky me - I have a closing problem and an opening problem!
By the way, it is a 1/3 HP - not a 3/4 HP as I stated in my previous post. The fact that Sears has this model (139.663701) in a list titled "Model numbers that are no longer Available" makes me wonder if it is older than I thought. Anyway I sent e-mail to Sears to see what they recommend. Unfortunately when I bought the residence the owner's manual was not included.
Thanks to all that replied.
Michael

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Disconnect it and operate by hand and maybe the cause will become apparent.
On Thu, 28 Apr 2005 17:53:46 GMT, "Michael T"

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Broken spring?

86&catalogId001&storeId001&langId=-1&productId8060864
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