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 Venstar T1800 backlight failure
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CDWillison
Junior Member

31 Posts

Posted - 05/11/2013 :  2:08:48 PM  Show Profile  Reply with Quote
We have recently had a problem with our venstar T1800. After just over a year of service the backlight seems to have failed (both button lighting and display letting, in all backlighting modes) given the price of this little gadget I am loath to replace it just for the backlight. Has anyone else had this issue is there any sort of simple fix (possibility to replace LED??)

Tfitzpatri8
Administrator

USA
10835 Posts

Posted - 05/11/2013 :  4:46:53 PM  Show Profile  Reply with Quote
I looked at the manufacturer's website and found something in the Troubleshooting section that might apply ( http://www.venstar.com/Support/?tab=troubleshooting ):

quote:

Erratic Operation, Partial Display, or Fluctuating Temperature
Symptom: This can be caused by a poor connection between the sub-base of the thermostat and the connection pins on the thermostat circuit board. Poor connection is usually caused by the sub-base being flexed against an uneven wall.

Correction: Loosen the screws that attach the sub-base to the wall, allowing it to flatten out, then snap thermostat back onto the sub-base.



If that doesn't fix it, there's also an email address on the same page for Venstar tech support.
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martynggreene
Starting Member

USA
3 Posts

Posted - 06/20/2013 :  08:09:16 AM  Show Profile  Reply with Quote
I installed 3 T1700's in March 2010. 2 of them have recently lost their backlight and on the other the LCD failed in March 2012. I reset them to factory defaults but that had no impact. I have emailed Venstar to complain about it, although I recognize that they are all outside the 1-Year Warranty period. It seems like a design or manufacturing issue to me.
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Tfitzpatri8
Administrator

USA
10835 Posts

Posted - 06/20/2013 :  08:23:45 AM  Show Profile  Reply with Quote
Did you follow that link above? There's a note in the troubleshooting section on the Venstar site about how poor connections between the thermostat and its wall mounting plate can cause display symptoms--doing a software reset won't help a bad physical connection. You might want to unplug the thermostat, verify the mounting plate is flat and level, inspect the pins for any damage, then carefully re-seat it.
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martynggreene
Starting Member

USA
3 Posts

Posted - 06/20/2013 :  7:18:55 PM  Show Profile  Reply with Quote
The new thermostat I bought works just fine in the same mounting plate. The ones with problems don't. It is not the mounting plate.
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[email protected]
Starting Member

1 Posts

Posted - 08/20/2013 :  11:49:38 PM  Show Profile  Reply with Quote
My T1800 backlight just went out as well -- after only 30 months. The product comes with only a 1 year warranty and my credit card provides an extra 1 year -- which is 6 months short of the failure. I am going to call Smarthome and bring this design flaw to their attention and see what they can do. We spend a premium to buy these home automation capable products and expect them to work.

My backlight was set to come on every night on the auto backlight mode setting... ironically, I was recently thinking of switching that to OFF and have it only come on when buttons are pressed.

quote:
Originally posted by martynggreene

I installed 3 T1700's in March 2010. 2 of them have recently lost their backlight and on the other the LCD failed in March 2012. I reset them to factory defaults but that had no impact. I have emailed Venstar to complain about it, although I recognize that they are all outside the 1-Year Warranty period. It seems like a design or manufacturing issue to me.

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Yepitsme
Starting Member

USA
1 Posts

Posted - 01/02/2014 :  8:49:26 PM  Show Profile  Reply with Quote
My T1800 thermostat is only 6 months old and the backlight has failed. Has anyone found a resolution to this problem?
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stusviews
Advanced Member

USA
15854 Posts

Posted - 01/02/2014 :  10:32:20 PM  Show Profile  Visit stusviews's Homepage  Reply with Quote
At only 6 months, there's a warranty solution.

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Please don't PM with questions that can be asked in a forum.
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arturk
Starting Member

USA
1 Posts

Posted - 10/27/2015 :  6:18:17 PM  Show Profile  Reply with Quote
I know this is very old thread but since I found solution I wanted to share it. I know there is many of you ot there still using Venstar T1700/T1800 thermostats.

Over the years I have acquired 4 thermostats for my House. I use them in Hydronic Radiant Floor setup with 4 Heating and 1 Cooling zone. They are part of my home automation system controlled by ISY-99i. In addition to many cool features I really like display backlight. Over the years backlight started fading and failing on one, then second and finally third unit. Usually it took 18-24 months for backlight to fail completely.
I searched web for solution but could not find any. However I found many reports about backlight failing for other users.

Finally I decided to try figure it out myself. After close inspection of the oldest unit, one of the resistors brought my attention since it looked really badly burned.

I am talking about resistor R45 you can see on below picture:


Here is another view, note how PCB trace is peeling off:


This is how slightly smoked but still working backlight resistor looks like:


On above picture you can see this is 470 Ohm (Code: 471). When I measured resistance on units with non working backlight I got nearly "infinite" resistance. This indicated completely burned resistor. Smoked one with backlight still working showed exactly 470 Ohms.

It looks like those SMD resistors do not have enough wattage for this application. I decided to use standard 1/4W Carbon Film "through-hole" type. You can get it at your local Radioshack. This type is easier to solder and another benefit is that exposed copper wires will provide additional cooling preventing resistor from overheating again.

I de-soldered old resistor by heating end with good trace/pad first (one not peeling off). This order is important if you do not want to mess-up good pad and it makes removal easier too. Just heat resistor end with the tip of your soldering iron and lift it slightly up. Trace on the other end will bend easily since it is detached from PCB due to heat damage. Them you can de-solder the other end or just simply cut loose part of the trace along with te resistor with utility knife. Be careful not to damage anything else or cut other traces. As alternative, if you have wider tip you can attempt to heat up entire surface of resistor hoping that both pads will get undone and resistor will stick to the tip of you iron. Do not heat for more that few seconds, otherwise you may damage PCB board badly and brake thermostat completely.

Form and cut connections of replacement resistor and make sure it fits in place perfectly. You are going have to scrape little bit of green protective enamel from trace right below mounting bolt so you can solder the other end of resistor. One end I solder to original pad.

This is how it should look like when it is done:
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Be very careful not short any connections when soldering. You will need low power iron with fine point/tip.
Inspect connections, if you are not certain you can use Ohmmeter to verify conductivity and check for possible shorts.

When you reinstall repaired thermostat you may realize backlight is not as bright as it was when unit was new. This is sign of backlight element aging as it is "fluorescent" kind and not LED. For this reason I turned backlight on all of my thermostats to "OFF". Check section 8 of Owner's Manual - "Turning On/Off the Backlight". By doing this backlight will only turn on for 8 seconds after pressing any key. This will ensure backlight will last for the lifetime of your thermostat. If you use "Auto" or "On" mode, it will continue wear out and will eventually get completely dark.

Good luck!
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xlurkr
Junior Member

43 Posts

Posted - 10/27/2015 :  9:26:21 PM  Show Profile  Reply with Quote
You are awesome.

I have one of these tstats, and though the backlight is fine, I now know what to do if it fails.

This is what the internet is for. Thank you.

-Tom
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martynggreene
Starting Member

USA
3 Posts

Posted - 11/03/2015 :  5:18:05 PM  Show Profile  Reply with Quote
I followed arturk's directions in replacing resistor and now have a T1700 with backlight to use as a swap in when others fails. I will keep a pack of 470 ohm resistors around. Great research and instructions. Thanks
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greanleaf
Starting Member

USA
1 Posts

Posted - 05/29/2016 :  2:37:32 PM  Show Profile  Reply with Quote
I followed Arturk's instructions, and had the same burnt out surface mount resistor on my T1700 thermostat. I replaced it with a 1/2 watt 440ohm carbon film through-hole resistor that I had laying around and the backlight works again! Thank you!!

Edited by - greanleaf on 05/29/2016 2:38:29 PM
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GordonGale
Starting Member

USA
1 Posts

Posted - 11/01/2019 :  7:21:49 PM  Show Profile  Reply with Quote
How can I get Arturk's reply with the pictures that are no longer included?
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BLH
Advanced Member

6178 Posts

Posted - 11/11/2019 :  03:44:50 AM  Show Profile  Reply with Quote
I have not seen the photos in any other places. I suspect the photo hosting site is either gone or the photos where too old to continue to host them.

You may find R45's ID silk screened on the board and replace it with the 470 Ohm 1/4W.
If you feel confident enough to do it without photos.
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