Honeywell digital thermostat no display

[RajaStyle]

Hi All

The screen has gone blank on our honeywell digital thermostat (pic attached), I've changed the batteries but nothing.

Any ideas what it could be and if a replacement is required is it easy to replace?

Many Thanks

 

[CBW]

Daft question, but did you use good quality batteries and insert in the correct polarity?

 

[JohnD]

Did the display go faint before it disappeared?

take out the batteries; check that they are good, clean the terminals with a nylon toothbrush and the lightest possible smear of WD40, check the direction of fitting of the new batteries.

i've heard that Duracell batts are slightly non-standard and not always a good fit.

Some of these timers have a built-in backup battery to keep the clock going during power loss, often bright green cylindrical. Nominally, it is not replaceable, but a person skilled in electronic assembly can solder in a new one. I think they last 5-10 years

is your stat wired? Or wireless?

 

[RajaStyle]

Did the display go faint before it disappeared?

take out the batteries; check that they are good, clean the terminals with a nylon toothbrush and the lightest possible smear of WD40, check the direction of fitting of the new batteries.

i've heard that Duracell batts are slightly non-standard and not always a good fit.

Some of these timers have a built-in backup battery to keep the clock going during power loss, often bright green cylindrical. Nominally, it is not replaceable, but a person skilled in electronic assembly can solder in a new one. I think they last 5-10 years

is your stat wired? Or wireless?

The stat is wired.. I tried two different types of batteries checking they are in the right way before inserting still blank and didn't go faint before disappearing that I am aware of.

I'll try cleaning the terminals with brush and wd40 as you suggest and let you know if worked.

 

[JohnD]

I think in some cases, the display goes blank if the electrical supply from the boiler goes off.

 

[JohnD]

btw, if it is wired, it is usually very easy to fit a replacement thermostat.

the stat is usually just an on-off switch, the boiler is not aware of the timer and thermostat controlling the switch.

You probably have two or three wires (plus an earth) in the cable in the wall. is that right?

 

[RajaStyle]

Yes I believe its just 3 coloured wires from memory, can it be replaced with a manual one or best to do like for like

 

[JohnD]

you can get a manual one cheaper. I like the electronic programmable ones. You can also get remote control versions operated by a smartphone, or learning your usage pattern, if you want

I don't like cordless or wireless ones, they go wrong too often, and cost more.

honeywell programmable 7-day ones are my favourite.

Examples

 

[RajaStyle]

I think in some cases, the display goes blank if the electrical supply from the boiler goes off.

How would I check this to rule it out?

 

[JohnD]

with a multimeter accross the coloured wires in the back

and verifying that your boiler is turned on, and the timer is at a "on" period.

 

[CBW]

How would I check this to rule it out?

Is the boiler or fused spur turned on?

 

[RajaStyle]

The stat is wired..

I'll try cleaning the terminals with brush and wd40 as you suggest and let you know if worked.

Brush and wd40 didn't work unfortunately. Found this article which may be worth a try?

https://polarclouds.co.uk/dt90e-repair/

The digital programmer is lit up And working fine just the room stat that's dead. Does that mean anything by way of electrics are fine?

 

[CBW]

You could try it, but seems a faff fo me, they’re cheap enough to replace.

 

[RajaStyle]

You could try it, but seems a faff fo me, they’re cheap enough to replace.

Thanks maybe your right £40 it is, hopefully it doesn't turn out to be the electrics

 

[CBW]

Thanks maybe your right £40 it is, hopefully it doesn't turn out to be the electrics

A multimeter is also cheap enough, if you want to rule that out 1st.