HVAC help: blank t-stat (by GA [GA]) Sep 23, 2018 12:55 PM
HVAC help: blank t-stat (by fred [CA]) Sep 23, 2018 1:21 PM
HVAC help: blank t-stat (by GA [GA]) Sep 23, 2018 1:46 PM
HVAC help: blank t-stat (by fred [CA]) Sep 23, 2018 1:59 PM
HVAC help: blank t-stat (by gevans [SC]) Sep 23, 2018 2:19 PM
HVAC help: blank t-stat (by GA [GA]) Sep 23, 2018 2:22 PM
HVAC help: blank t-stat (by myob [GA]) Sep 23, 2018 2:24 PM
HVAC help: blank t-stat (by GA [GA]) Sep 23, 2018 2:34 PM
HVAC help: blank t-stat (by GA [GA]) Sep 23, 2018 2:45 PM
HVAC help: blank t-stat (by cjo'h [CT]) Sep 23, 2018 6:51 PM
HVAC help: blank t-stat (by gevans [SC]) Sep 23, 2018 6:55 PM
HVAC help: blank t-stat (by cjo'h [CT]) Sep 23, 2018 7:36 PM
HVAC help: blank t-stat (by gevans [SC]) Sep 24, 2018 4:02 AM
HVAC help: blank t-stat (by Vee [OH]) Sep 24, 2018 4:23 AM
HVAC help: blank t-stat (by Jason [VA]) Sep 24, 2018 9:17 AM
HVAC help: blank t-stat (by GA [GA]) Posted on: Sep 23, 2018 12:55 PM Message:
Painter at a turnover unit complains there is no ac there. If it had not worked two weeks ago I would have both gotten complaints, and noticed it at move out. T-stat screen is empty.
1. Checked all breakers, including the one at the condenser, and none are tripped.
2. Replaced batteries in t-stat. Screen still blank.
3. Installed new t-stat. Screen still blank.
4. Put red wire to green wire at t-stat, and fan comes right on. Put red wire to yellow wire at t-stat and ac compressor jumps on. So I think the wire is not shorted and the units have power.
5. Checked the overflow, and it seems fine and not stuck
Googled around a bit and found it may be either the transformer at the furnace circuit board, or a short in the overflow switch. Do either of these sound correct? If so, how do I test for which one of these is the problem so I know which one to replace? Is there a good DIY website?
Since the unit is empty I'd have to take off work to meet a tech, so it is much for efficient for me to fix this nights & weekends, if I can figure out how to fix it. Thanks in advance for any help. --73.106.xxx.xxx |
HVAC help: blank t-stat (by fred [CA]) Posted on: Sep 23, 2018 1:21 PM Message:
The transformer provides 12V to the T stat. Replace it and see if your T stat gets powered..
They sell for as little as $10. --99.59.x.xxx |
HVAC help: blank t-stat (by GA [GA]) Posted on: Sep 23, 2018 1:46 PM Message:
Thanks. Aftermarket transformers seem to cost about $50 for my unit, per this
https://www.supplyhouse.com/Heil-Quaker-1011626-115V-Primary-24V-Secondary-40VA-Transformer
Are there less expensive ones that will do the same thing that I should be looking at? --73.106.xxx.xxx |
HVAC help: blank t-stat (by fred [CA]) Posted on: Sep 23, 2018 1:59 PM Message:
Shop for a universal transformer. With some skill, you can make it work for your unit.
I have done this before. Disconnect the power to the unit, label the wires with stickers, remove the old transformer, take it to an electric supply outlets. I'm sure they will be able to find one that would have the same wires to fit, for less money.
Since you attach it to the wall of the unit wherever you have space, the actual size wouldn't matter.
And yes, it's 24V, my mistake. --99.59.x.xxx |
HVAC help: blank t-stat (by gevans [SC]) Posted on: Sep 23, 2018 2:19 PM Message:
If you can bring on the fan by touching the thermostat wires together, the transformer is still working. You need a new thermostat.
And no offense, but you need someone else to install it or you WILL need a new transformer.
PS. 24 volt transformers are generic. I can buy them all day for under $10 bucks. Or even better, rob one off a dead furnace or air handler. Free. --98.122.x.xx |
HVAC help: blank t-stat (by GA [GA]) Posted on: Sep 23, 2018 2:22 PM Message:
Thanks Gevans. I did replace the thermostat - but even the new one is blank...I suppose it is possible the old t-stat went bad and the new one I bought was a bad one, but I think its unlikely. What else should I check? --73.106.xxx.xxx |
HVAC help: blank t-stat (by myob [GA]) Posted on: Sep 23, 2018 2:24 PM Message:
call me crazy but I think the batty operate t/states show somehting even when not hooked up? It uses 2 AA batt's? I guess you put newer ones in and the rigth polarity-- sorry just asking.
As far as transformer-- use OEM parts. No "make it work" on furnaces. --99.103.xxx.xxx |
HVAC help: blank t-stat (by GA [GA]) Posted on: Sep 23, 2018 2:34 PM Message:
Also Gevans - no offense taken, but in reading your comment more closely, you warned I should not install the tstat. To clarify, I did not accidentally touch the wires as described in my first post - I turned the power off at the breaker, isolated all the wires, then methodically only touched red to yellow and turned power back on at breaker, and later red to green in order to test it, as I was taught to do many years ago. Was I taught incorrectly and and is that is not a good test? --73.106.xxx.xxx |
HVAC help: blank t-stat (by GA [GA]) Posted on: Sep 23, 2018 2:45 PM Message:
myob - the more expensive t-stats might, but I just tested mine at home, which has 2 AAA's replaced a few weeks ago (ie they are fine) and as soon as I remove the T-stat from the wall mount the display goes blank.
As for the rental, when the t-stat first went out, I used AAA batteries I had, and when that did not work, I bought new batteries, and 2x checked they were properly installed. The new T-stat I bought uses a flat coin type CR2025 battery that came with it. I also replaced that with a new CR2025 I had and it still does not work. I've replaced many t-stats over the years and never had a problem. --73.106.xxx.xxx |
HVAC help: blank t-stat (by cjo'h [CT]) Posted on: Sep 23, 2018 6:51 PM Message:
GA,I don't like thermostats that have to have batteries.and why was your painter complaining about the A/C,thought he was there to work,instead of just being in a cruise environment.........charlie........................................ --32.214.xxx.xx |
HVAC help: blank t-stat (by gevans [SC]) Posted on: Sep 23, 2018 6:55 PM Message:
GA:
You are using the correct test. I was concerned that you did not know there had to be transformer power for this test to work, but were considering the possibility of a bad transformer. This indicates a lack of basic electrical circuit knowledge... something most people are deficient in.
I did not intend to slur your abilities, but rather to save your transformer and your pocketbook by suggesting you get someone qualified to hook it up.
As far as I know, every thermostat that takes batteries will operate without hooking up ANY wires. If you are getting a blank screen, the problem is with either the thermostat or that batteries. --98.122.x.xx |
HVAC help: blank t-stat (by cjo'h [CT]) Posted on: Sep 23, 2018 7:36 PM Message:
GKARL, I think Gevans went to Blarney and kissed the Stone, but forgot to mention it...................charlie.................. --32.214.xxx.xx |
HVAC help: blank t-stat (by gevans [SC]) Posted on: Sep 24, 2018 4:02 AM Message:
cjo'h,
not the first time I have been told that. LOL --98.122.x.xx |
HVAC help: blank t-stat (by Vee [OH]) Posted on: Sep 24, 2018 4:23 AM Message:
If the unit works by touching wires you need a new t-stat/control, if you can find a mechanical one that would just fine, I use the blue ones from supply house with 3 inch numbers, kinda like adding grab bars in every shower it just makes sense. --76.188.xxx.xx |
HVAC help: blank t-stat (by Jason [VA]) Posted on: Sep 24, 2018 9:17 AM Message:
Just brainstorming here, but it sounds like your thermostat is missing a common from the transformer. Check for a bad joint in the air handler.
Your methodologies for testing are spot on, by jumping R to G, you’re energizing the blower relay. However, that relay has its common sourced directly from the air handler, which is independent from the Tstat.
Check voltage between r and c (common). If you don’t have 24vac there, that’s your problem, an open common. --65.118.xx.xxx |
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