Honeywell central heating programmer keeps turning on & off

Jakg

I bought my house back in march and it came with a Honeywell ST9400C programmer, connected to a Worcester HeatSlave 20-25 boiler with a Honeywell DT92E Wireless Room Thermostat.

Randomly it gets stuck where the programmer keeps turning on and off with a "click" each time it turns off. It started doing it every 10 seconds or so, then went away but now its come back and is doing it every 2-3 seconds!

I've tried reseating the unit on it's baseboard, all the pins look good.

Quick video of what I mean here - https://youtu.be/gF7VfyUnjH0

I've Googled to no avail so I thought I'd turn to MSE... help?

Ruski

Get onto honeywell customer services - email the link to the video and see if you're lucky - we've had some positive feedback on their customer service recently

Good luck

Russ

southcoastrgi

if it's correctly connected to the base plate then i'd check the wiring connections are done up tight at both ends & not arking

Jakg

To update this - got worse to the point that I couldn't actually turn the heating on at all. No reply from Honeywell, got a replacement for £30 on eBay and now it works perfectly.

bsod

too late for you, some of these Honeywell st9400c timers (made around 2010/11) are faulty and display similar symptoms eg

flashing display and clicking relays

everything on the timer appears normal, but the boiler/pump doesn't fire up

or heating and hot water not working at the same time (and display flashes), but one works at a time intermittently

switching off and on at the mains a few times can sometimes make it work

The workaround is to go into installer mode and turn off the backlight (page 12 of the manual), or call Honeywell for a free replacement (doesn't have to be in warranty)

put switch into run position
hold ok and - for 8 seconds
press ok
there are 8 possible parameters to change, the only one that needs changing is parameter 2 (backlight) to zero (off) using +/- buttons and ok
move slider switch to set heating or water position, then back to run

Jakg

bsod wrote: »

too late for you, some of these Honeywell st9400c timers (made around 2010/11) are faulty

The workaround is to go into installer mode and turn off the backlight (page 12 of the manual), or call Honeywell for a free replacement.

I did come across this, but mine wasn't one of the faulty batch.

The new one I bought from eBay didn't work either in the end! It looked like it worked, the lights came on etc - but it never made the circuit - unless the backlight was off (not quite the same failure as described online).

Luckily, the replacement was part of the faulty batch - so I got in touch with Honeywell (again) and they sent me out an actual new one for free.

Maybe I should just of got a Nest...

bsod

https://nest.com/support/article/What-to-do-if-your-Nest-Thermostat-has-become-slow-unresponsive-or-won-t-turn-on