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Old 03-04-2012, 03:05 PM   #1
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thermostat LED screen dead


people,

Another ac problem this week....LOL

This time, my Mother's house- shes not a member here, so hey, I told her Id post it- her Honeywell thermostat all of a sudden went dead, no led light showing the temperature. Its a Honeywell T8411R. Not sure if that helps.

I went to the box and no breakers are flipped/tripped. It worked yesterday.

Only other thing I can offer is I drew the colored wires:

On the left side, Green, Blue, Red, Yellow

On the right side, White, Orange.

Tips/advice always appreciated!!!

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Old 03-04-2012, 03:32 PM   #2
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thermostat LED screen dead


It looks as though this thermostat is dependant on power from the furnace.

Meaning it has no batteries.

If you have a volt meter measure voltage from terminal R and C. You should have 24 vac. If you do then its the stat if you do not then there could be several more things to check.

Such as
1. Power to the furnace
2. Power out of the transformer
3. Fuse blown on the control board (If you have one)
4, Open circuit from furnace to stat

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Old 03-04-2012, 03:47 PM   #3
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thermostat LED screen dead


If it has batteries change them. If not they die from old age and sometimes people accidentally zap them with static electricity. Most likely old age.
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Old 03-04-2012, 06:11 PM   #4
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24Vs from the transformer check it right down in the furnace.solid stat board(if it has one) lite up leds? at the stat subbase jump R to W see if you get a cycle....can you read 24Vs off blue/yellow of the TR
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Old 03-04-2012, 06:53 PM   #5
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thermostat LED screen dead


Thanks, people, for the help. No batteries visible when I snapped off the stat from the wall plate. Man, I know the above steps to check are kinda tricky for me- a novice here, but maybe I could buy a new one at HD and snap in in and see if it works, then if still it doesnt, I could return it in good faith(?), and go from there? This way, if the stat is bad, problem solved, I figure, eh?
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Old 03-04-2012, 06:55 PM   #6
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Quote:
Originally Posted by biggles View Post
24Vs from the transformer check it right down in the furnace.solid stat board(if it has one) lite up leds? at the stat subbase jump R to W see if you get a cycle....can you read 24Vs off blue/yellow of the TR
Now, this I can do easy. Have to wait til my next visit to Moms house, though. Could be a few days, so I appreciate the patience meanwhile, until I post results....
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Old 03-12-2012, 08:11 PM   #7
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Quote:
Originally Posted by Plumber101 View Post
It looks as though this thermostat is dependant on power from the furnace.

Meaning it has no batteries.

If you have a volt meter measure voltage from terminal R and C. You should have 24 vac. If you do then its the stat if you do not then there could be several more things to check.

Such as
1. Power to the furnace
2. Power out of the transformer
3. Fuse blown on the control board (If you have one)
4, Open circuit from furnace to stat
Took a while, but got over there and Plumber101 was right- blown fuse in circuit board/control board(?). So, I poked around a bit (with power off!), and found the low voltage wire bundle at the outside of the house where it exits the metal channel were all chewed up./chaffed! Geez- probably rats/squierrels.

Well, pretty good detective work for a greenhorn. Of course, with the great help from the members here. So nnow, gotta find a way to feed/force a new wire sheath/bundle down the chute from the attic. Maybe I can crawl closest possible to the eave, then lower the end of the wire with a 2-3 oz lead fishing weight? Then I need to cut all, and twist tie each color and wrop well with tape, huh?

Thnaks!
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Old 03-13-2012, 09:23 AM   #8
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thermostat LED screen dead


Try This: Join old stat wire to new stat wire by twisting them around one another length wise and tightly wrap them in two layers of GOOD electrical tape.

Now with one person in the attic pulling the old wire up thru the wall/ceiling and one person at the stat exit point feeding the new stat wire, run the new wire.

hope this helps....

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