Honeywell digital thermostat no display

[Harry Bloomfield]

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

As cheap as maybe £10 and might well come in handy in the future.

 

[Harry Bloomfield]

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

Not usually where there are replaceable batteries fitted, the batteries maintain the clock when mains power is absent.

 

[RajaStyle]

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?

Thanks all managed to do it, just used this article and scraped the connectors on the circuit board and seemed to sort it.

 

[Steamerpoint]

I had the same problem. Blank screen. Changed batteries, but still nothing. Wondered if one if the kids had knocked it off the window sill and batteries weren't making proper contact. Took back off by pushing two clips in battery bay so I could see the circuit board then from the back eased the positive battery terminals inwards towards where the batteries would be. I then popped the batteries back in the bay and straight away it powered back up again.

So there seems to be a design fault centered around the positive battery terminals. They are recessed and it is possible for the body of the battery to sit against the plastic in front of the terminals, without the positive part of the battery actually making contact with the positive terminals.

Popped the back on again and still working a treat.

 

[Harry Bloomfield]

So there seems to be a design fault centered around the positive battery terminals. They are recessed and it is possible for the body of the battery to sit against the plastic in front of the terminals, without the positive part of the battery actually making contact with the positive terminals.

Not so much a design fault of the unit, more a to do with the variations in design of the batteries. I've come across the issue before, where the positive cap, is not as proud as normal - and they simply will not connect, where the battery holder has a recessed terminal.

 

[JohnD]

Duracell batteries are not quite normal dimensions

 

[CBW]

Not so much a design fault of the unit, more a to do with the variations in design of the batteries. I've come across the issue before, where the positive cap, is not as proud as normal - and they simply will not connect, where the battery holder has a recessed terminal.

I’ve had the same issue with the batteries that Honeywell supply, so I think it’s a crap design.