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-   -   RUUD Achiever 90 plus small blower won't turn off (http://www.diychatroom.com/f17/ruud-achiever-90-plus-small-blower-wont-turn-off-16695/)

tahoeboy50 02-06-2008 05:50 PM

RUUD Achiever 90 plus small blower won't turn off
 
I have a RUUD mode UGTA-07EMAES furnace. It was working fine now the small blower stays on all the time, no heat. This has happened before and the service guy reset the over temp switch and told me to clean the filters. I put new ones in and it ran for months. Now it is bad again. The filters are not new now, but they are reasonable clean. Question: could the main blower be running too slow and not enough air going over the burners? Or could someone shut too many vents? Or could the over heat sensor be bad? The furnace is about 4 years old and not used much.. I have the ability to use a volt-ohm meter. What do the lights on the unit tell me???
thanks..

har199 02-08-2009 07:45 PM

If the small blower motor keeps running usually the safety limit switch(over temp switch) has popped and needs to be manually reset.

JohnH1 02-08-2009 09:47 PM

Quote:

Originally Posted by tahoeboy50 (Post 95558)
I have a RUUD mode UGTA-07EMAES furnace. It was working fine now the small blower stays on all the time, no heat. This has happened before and the service guy reset the over temp switch and told me to clean the filters. I put new ones in and it ran for months. Now it is bad again. The filters are not new now, but they are reasonable clean. Question: could the main blower be running too slow and not enough air going over the burners? Or could someone shut too many vents? Or could the over heat sensor be bad? The furnace is about 4 years old and not used much.. I have the ability to use a volt-ohm meter. What do the lights on the unit tell me???
thanks..

Re: Question: could the main blower be running too slow and not enough air going over the burners? Or could someone shut too many vents? Or could the over heat sensor be bad? The answers are Yes, Yes and Yes among many other things. A unit can only cycle on the limit so many times before it becomes weak or fails compleatly. If it is the hi limit failing the tempature rise needs to be checked and compaired to the furnace tag. It is usually in the 30 to 60deg range.:)

beenthere 02-09-2009 07:04 AM

You put new filters in months ago.

Try installing new filters again and resetting.

Air filter looks can be disceiving.

Dick Ecker 09-14-2010 01:06 PM

Ruud Achiever 90 plus small blower
 
I just fixed my Ruud UGRA09EZAJS. This fall when fired up, the forced draft blower (small blower) was found to be running and the gas had shut off.
One of the hard to reach RE-SETTABLE limit switches was open (popped).

I found the culprit right away. A chipmunk had invaded the air intake pipe (3 inch pvc plastic) and partially clogged the pipe with his nest and about 2 pounds of bird seed from my bird feeder.

I used a very big shop vacuum cleaner to altrenately suck and blow on the pipe which enters the burner area in the upper right corner of the inspection area.

I was able to dislodge a nest and tree leaves and a whole lot of bird seed, and suck it up in my shop vacuum.
I have added 1/2 inch mesh hardware cloth screening to my outside air intake and exhaust pipes to prevent future trouble.

If your plenum limit switch is causing your heat to cycle then you might have a dirty filter problem, but, the re-settable limit switches would indicate your problem is with incoming cool air from outside not cooling the limit switch.
This problem caused me quite a bit of trouble.
Unfortunately, restrictions in air intake lines must be cleaned out by opening the pvc pipe at probable joints/elbows to get access with a clean out vacuum cleaner.
Access to the re-rettable thermostat limit switches is extremely difficult and should be addressed by Ruud/Rheem.

hvaclover 09-14-2010 02:32 PM

Reasonably clean is not the same as actually clean.


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